WO2024090370A1 - Magnetic domain wall moving element, memory device, and data writing method - Google Patents
Magnetic domain wall moving element, memory device, and data writing method Download PDFInfo
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- WO2024090370A1 WO2024090370A1 PCT/JP2023/038152 JP2023038152W WO2024090370A1 WO 2024090370 A1 WO2024090370 A1 WO 2024090370A1 JP 2023038152 W JP2023038152 W JP 2023038152W WO 2024090370 A1 WO2024090370 A1 WO 2024090370A1
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- G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
- G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/82—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by variation of the magnetic field applied to the device
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B61/00—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
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- H10N50/10—Magnetoresistive devices
Definitions
- the present invention relates to a domain wall motion element, a memory device, and a data writing method.
- Patent Document 1 describes a method for manufacturing a domain wall motion element in which a magnetization free layer is formed so as to be magnetically coupled with both a first and a second pinning layer whose magnetization directions are fixed in opposite directions, and a domain wall motion region in which the magnetization direction is set to the first direction or the second direction is formed in the magnetization free layer.
- Magnetic memory devices as non-volatile memories are able to retain internal data even when power is not being supplied, which is a great energy-saving effect.
- Such magnetic memory devices use ferromagnetic materials, and the magnetic pole information (information on the perpendicular binary state) is recorded internally as digital information.
- magnetic memory devices using ferromagnetic materials have a limited domain wall motion speed, so there is a limit to how much the operating speed can be improved.
- the technology described in Patent Document 1 is related to the initialization of domain wall motion elements, and does not solve these problems.
- the present invention was made in consideration of these problems, and realizes a domain wall motion element, memory device, and data writing method that can improve the domain wall motion speed.
- the domain wall motion element is made of an antiferromagnetic material having a non-collinear spin structure, and is provided with an antiferromagnetic layer having a domain wall that moves in one direction when a current is applied.
- the antiferromagnetic material may be any one of Mn3Ge , Mn3Sn , Mn3Ga , Mn3Rh , Mn3Pt , and Mn3Ir .
- the antiferromagnetic material may have a kagome lattice as a crystal structure, and the one direction in which the domain wall moves may be a direction approximately perpendicular to the normal vector of the plane formed by the kagome lattice.
- the antiferromagnetic layer may be made of a single crystal.
- the domain wall motion element may further include a spin Hall layer that contains at least one of Pt, Ta, and W and is stacked on the antiferromagnetic layer, and that exhibits the spin Hall effect when a current is applied.
- a spin Hall layer that contains at least one of Pt, Ta, and W and is stacked on the antiferromagnetic layer, and that exhibits the spin Hall effect when a current is applied.
- a memory device includes a domain wall motion element having an antiferromagnetic layer made of an antiferromagnetic material having a non-collinear spin structure, a write unit that writes data into the magnetic domain by determining the magnetization direction of the magnetic domain in the antiferromagnetic layer, and a read unit that reads the magnetization direction of the magnetic domain that has moved within the domain wall motion element by applying a current to the antiferromagnetic layer.
- the writing unit may have a photoelectric conversion element that outputs an electrical signal according to input light, and may use the electrical signal output by the photoelectric conversion element to control the magnetization direction of the magnetic domain and write data to the magnetic domain.
- a data writing method includes a first step of writing data to a magnetic domain by controlling the magnetization direction of the magnetic domain of an antiferromagnetic layer made of an antiferromagnetic material having a non-collinear spin structure, and a second step of moving the magnetic domain in one direction of the antiferromagnetic layer by applying a current to the antiferromagnetic layer.
- the first and second steps may be repeated multiple times.
- the present invention makes it possible to realize a domain wall motion element, a memory device, and a data writing method that can improve the domain wall motion speed.
- FIG. 2 is a diagram showing a magnetic structure of a non-collinear antiferromagnetic body according to the first embodiment; FIG. 2 shows the anomalous Hall effect of Mn 3 Ge.
- FIG. 1 is a diagram showing a method for domain wall motion in a Mn 3 Ge thin wire.
- FIG. 2 is a diagram showing the magnetic domain wall motion of Mn 3 Ge in time series.
- 1 is a graph showing the state of domain wall motion in Mn 3 Ge.
- FIG. 13 is a diagram showing a state when a shift current for moving a domain wall flows in a kagome plane of Mn 3 Ge.
- 1 is a graph showing the state of domain wall motion in Mn 3 Ge.
- FIG. 13 is a diagram showing the positional relationship between a shift current and a Kagome surface.
- FIG. 1 is a diagram illustrating the mechanism of domain wall motion in a ferromagnetic material.
- 1A and 1B are diagrams illustrating a detailed mechanism of domain wall motion in a ferromagnetic material.
- FIG. 1 is a diagram showing a detailed mechanism of domain wall motion in Mn 3 Ge. 1 is a graph showing the relationship between the width of a domain wall and the amount of spin accumulation in Mn 3 Ge. 1 is a graph showing the domain wall velocity of each material measured by an experiment.
- 1A to 1C are configuration diagrams showing variations of domain wall motion elements.
- FIG. 11 is a schematic configuration diagram of a memory device according to a second embodiment.
- FIG. 1 is a diagram showing the mechanism of domain wall motion in Mn 3 Ge.
- FIG. 2 is a block diagram showing a unit relating to control of a register section.
- FIG. 2 is a detailed configuration diagram of a magnetoresistance element.
- First embodiment (1A) 1 is a diagram showing the magnetic structure of Mn 3 Ge, an antiferromagnetic material having a non-collinear spin structure (hereinafter also referred to as a non-collinear antiferromagnetic material), which is an element of a domain wall motion element.
- Mn 3 Ge has a crystal structure in which kagome lattices made of magnetic atoms Mn (manganese) are stacked in the c-axis direction, and FIG. 1 shows the magnetic structure of one kagome plane of the kagome lattice.
- Ge germanium
- Mn forms a hexagonal structure on the inside.
- the direction of the spin of each Mn atom is indicated by an arrow. Note that in Fig. 2 and subsequent figures showing the kagome surface of Mn 3 Ge, the direction of the spin of each Mn atom is similarly indicated by an arrow.
- Fig. 1(A) the spins of adjacent Mn atoms are offset by 120 degrees from each other.
- This structure is called an inverted 120-degree structure, and Mn 3 Ge is in an antiferromagnetic order (or chiral antiferromagnetic order).
- the Mn spins in the entire hexagon exhibit a weak ferromagnetic moment, also called a magnetic octupole, which determines the micromagnetization direction of Mn 3 Ge.
- the magnetic octupole has a magnetization direction H1 shown as a downward arrow in Fig. 1(A).
- the orientation of the magnetic octopole is opposite in Fig. 1(A) and (B).
- the state of Fig. 1(A) and (B) can be switched between each other, so that the non-collinear antiferromagnet can also be used as a memory that records the state of "0" or "1".
- An antiferromagnet with such a minute magnetization is also called a canted antiferromagnet.
- Fig. 2 is a diagram showing the anomalous Hall effect of Mn 3 Ge.
- the kagome planes of Mn 3 Ge are stacked so as to be perpendicular to the [0001] direction, which is the planar direction of the Mn 3 Ge layer M (antiferromagnetic layer).
- Mn 3 Ge is polarized by magnetic octopoles, so a large virtual magnetic field H is generated in the [01-10] direction in the antiferromagnetic layer M.
- 3A to 3C show the state of domain wall motion in a thin wire of Mn 3 Ge.
- a method of domain wall motion in a thin wire of Mn 3 Ge will be described with reference to FIG.
- the Mn 3 Ge thin wire N has a shape extending in the [2-1-10] direction.
- a write current C By passing a write current C through this thin wire N in the [0001] direction perpendicular to the [2-1-10] direction, a magnetic domain D1 having magnetic domain walls at both ends is generated.
- This magnetic domain wall is a Neel wall.
- a pulse current t having a pulse width on the order of nanoseconds through the thin wire N in the negative direction of [2-1-10]
- the magnetic domain D1 moves to the position of the magnetic domain D2 shown in FIG. 3A.
- This pulse current t is also called a shift current.
- 3B is a diagram showing the magnetic domain wall movement of Mn 3 Ge in a time series.
- a state in which a magnetic domain (magnetic domain wall) is generated in the thin wire N by the write current C is shown.
- the magnetic domain moves in the positive direction by the pulse current t.
- time t3 which is later in the time series than time t2, the magnetic domain moves further in the positive direction by the pulse current t.
- Fig. 3C is a graph showing the state of domain wall movement in Mn3Ge .
- data shown by triangular dots indicates data when the direction of the magnetic domain movement distance x and the direction of the pulse current t are positive, and data shown by circular dots indicates data when the direction of the magnetic domain movement distance x and the direction of the pulse current t are negative.
- the horizontal axis of the graph in Fig. 3C indicates the current density j of the pulse current in the fine wire N, and the vertical axis indicates the domain wall movement speed V.
- Fig. 3C shows that when the absolute value of the current density j is approximately 4* 1010 (A/ m2 ) or more, the domain wall moves at a constant speed or more.
- the Mn 3 Ge thin wire can be used as a domain wall motion element.
- the mechanism of domain wall motion in Mn 3 Ge will be further explained below.
- FIGS. 3A to 3C are diagram showing a state when a shift current j flows through the kagome surface of Mn 3 Ge to move the domain wall.
- the kagome surface K is located on the xy plane, and the z-axis direction is defined as the normal direction of the kagome surface K.
- the x-axis direction is the [2-1-10] direction
- the y-axis direction is the [01-10] direction
- the z-axis direction is the [0001] direction.
- the angle that the vector of the shift current j makes with the z-axis is defined as ⁇ . Note that the domain wall in Mn 3 Ge moves in the opposite direction to the vector direction of the shift current j, as shown in FIGS. 3A to 3C.
- Fig. 4B is a graph showing the state of domain wall motion in Mn3Ge when ⁇ is 0°, 45°, 60°, and 90°.
- the horizontal axis of the graph in Fig. 4B indicates the absolute value of the current density j of the shift current, and the vertical axis indicates the domain wall motion speed V.
- the shift current j flows within the plane of the kagome surface.
- the spin polarization of Mn 3 Ge related to the shift current j is a non-zero value.
- the moving domain wall is a Neel domain wall.
- the vector of the shift current j is perpendicular to the plane of the kagome surface K.
- the moving domain wall is a Bloch wall.
- Fig. 4B for any value of ⁇ , as explained in Fig. 3C, it is shown that the larger the absolute value of the shift current j, the greater the movement speed V.
- Figure 5 shows the mechanism of domain wall movement in a ferromagnetic material.
- the arrows indicate the direction of spontaneous magnetization (magnetic moment) in the ferromagnetic layer F.
- the direction of the magnetic moment changes in the center of the ferromagnetic layer F, and this location becomes a domain wall.
- the right and left sides of the ferromagnetic layer F on either side of the domain wall form different magnetic domains.
- (II) shows the state in which a shift current flows from the state shown in (I) to the left side of Figure 5.
- the shift current passes through the domain wall, the electron spin interacts with the magnetic moment, transferring the electron spin angular momentum to the magnetic moment. This causes the magnetic moment to rotate, and the domain wall to move to the right side of Figure 5.
- This mechanism of transferring spin angular momentum is also called spin transfer torque.
- (III) shows a state in which the magnetic moment has rotated, and as a result, the magnetic domain wall has moved toward the right side of Fig. 5 compared to (II). If the moving speed of the magnetic domain wall in such a ferromagnetic material is u, then u can be expressed by the following equation. u ⁇ (J P) / Ms ... (1)
- J is the current density of the shift current
- P is the spin polarization of the ferromagnetic material
- Ms is the magnitude of magnetization.
- Mn 3 Ge which is a non-collinear antiferromagnetic material
- the domain wall in Mn 3 Ge can move. Therefore, in a non-collinear antiferromagnetic material, the spin polarization is not considered to be a factor in the domain wall movement.
- Fig. 6A is a diagram showing a detailed mechanism of domain wall movement in a ferromagnetic material.
- Fig. 6A shows a state in which, when a current j flows through a ferromagnetic material having spontaneous magnetization ⁇ , the magnetic moment in the ferromagnetic material rotates under the torque ⁇ stt derived from the spin angular momentum of electrons described in Fig. 5.
- the current j flows in the positive direction of the x-axis, and the domain wall moves in the negative direction of the x-axis.
- Fig. 6B is a diagram showing a detailed mechanism of domain wall motion in Mn 3 Ge, in which when a current j is applied to Mn 3 Ge having a spontaneous magnetization ⁇ , a magnetic octupole of Mn 3 Ge receives a torque ⁇ eff and rotates.
- Fig. 6C is a graph showing the relationship between the domain wall width L and the spin accumulation amount Sa per unit electric field in Mn 3 Ge.
- graphs are shown for both the Neel domain wall and the Bloch domain wall.
- the absolute value of the spin accumulation amount Sa per unit electric field increases as the domain wall width L decreases.
- the torque ⁇ eff described above increases, and the domain wall can be moved at a higher speed.
- Fig. 7 is a graph showing the domain wall velocity when various materials are used as the domain wall motion element in an experiment.
- the vertical axis of the graph in Fig. 7 shows the domain wall motion velocity V at the normalized current density.
- Fig. 7 shows the following materials: Mn 3 Ge, which is an antiferromagnetic material (AFM); Pt/BiYIG/GSGG, Mn 4-x Ni x N, and GdCo/Pt, which are ferrimagnetic materials (FI); SAF1, SAF2, and SAF3, which are synthetic antiferromagnetic materials (SAF); Pt/Co/AIO x , which are ferromagnetic materials (FM); and permalloy.
- AFM antiferromagnetic material
- Pt/BiYIG/GSGG Pt/BiYIG/GSGG
- Mn 4-x Ni x N and GdCo/Pt
- FI ferrimagnetic materials
- SAF1, SAF2, and SAF3 synthetic antiferromagnetic materials
- SAF1 is TaN/Pt/Co/Ni/Co/Ru/Co/Ni/Co/TaN
- SAF2 is Ta/Pt/Co/Ni/Co/Ru/Co/Ni/Co/Ta
- SAF3 is TaN/Pt/Co/Ni/Co/Ru/Ru/Co/Ni/Co/TaN.
- Mn 3 Ge has an overwhelmingly high domain wall motion velocity V compared to other materials such as ferrimagnetic materials, synthetic antiferromagnetic materials, and ferromagnetic materials. Therefore, by applying Mn 3 Ge to a domain wall motion element, it is possible to improve the domain wall motion velocity.
- the non-collinear antiferromagnetic material is Mn 3 Ge, but the non-collinear antiferromagnetic material according to the present invention is not limited to Mn 3 Ge.
- the non-collinear antiferromagnetic material according to the present invention may be another type of compound as long as it is made of an antiferromagnetic material having a non-collinear spin structure and has an antiferromagnetic layer having a domain wall that moves in one direction when a current is applied.
- An example of another type of compound is a manganese compound, and an example of this is Mn 3 X (X is any of Ge, Sn, Ga, Rh, Pt, Ir, etc.).
- the thickness of the antiferromagnetic layer (i.e., the thickness of the antiferromagnetic layer in the direction perpendicular to the plane of the antiferromagnetic layer through which the shift current that moves the domain wall flows) may be, for example, on the order of tens to hundreds of nm. Furthermore, the size of the film thickness is not limited to this.
- the non-collinear antiferromagnetic material used in the domain wall motion element is produced as a single crystal rather than a polycrystal.
- a single crystal is ideally a crystal in which the direction of the crystal axis is the same in every part of the crystal, but it also includes crystals that partially contain at least either lattice defects or minute changes in the direction of the crystal axis.
- polycrystals single crystals are stacked in a regular pattern, so pinning sites are less likely to occur and domain walls are more likely to move smoothly.
- Single crystals can be produced by any known crystal growth method.
- the non-collinear antiferromagnetic material incorporated in the domain wall motion element may be processed by cutting it out with a focused ion beam (FIB).
- FIB focused ion beam
- the domain wall motion element may be created by forming a layer of the non-collinear antiferromagnetic material on the surface of a different object by film deposition.
- the domain wall motion element can be configured to include an antiferromagnetic layer made of a non-collinear antiferromagnetic material and having a domain wall that moves in one direction when a current is applied.
- this antiferromagnetic material when a current is applied, spin accumulation is formed around the domain wall, causing the domain wall to move. Due to this mechanism, such an antiferromagnetic material can improve the domain wall motion speed compared to other magnetic materials such as ferrimagnetic materials, synthetic antiferromagnetic materials, and ferromagnetic materials. From another perspective, such an antiferromagnetic material can reduce the current value required to move the domain wall at the same speed compared to other magnetic materials, and therefore can be said to have an energy-saving effect.
- the antiferromagnetic material may be, for example, any one of Mn3Ge , Mn3Sn , Mn3Ga , Mn3Rh , Mn3Pt , and Mn3Ir .
- the antiferromagnetic material may have a kagome lattice as a crystal structure, and the direction in which the domain wall moves (or the direction in which the shift current is applied) may be approximately perpendicular to the normal vector of the plane formed by the kagome lattice.
- the direction in which the domain wall moves may form a vector that is approximately parallel to the kagome plane.
- approximately parallel means that the direction in which the domain wall moves is parallel to the kagome plane or nearly parallel (for example, the angle between the direction in which the domain wall moves and the kagome plane is a few degrees or less). This can further increase the domain wall motion speed.
- the antiferromagnetic layer may also be made of a single crystal. This configuration makes it difficult for pinning sites to occur and makes it easier for the domain walls to move smoothly, thereby making it possible to further increase the domain wall movement speed.
- Fig. 8 is a configuration diagram showing a variation of the domain wall motion element.
- the domain wall motion element T includes a domain wall motion layer 11 made of Mn 3 Ge, and a spin Hall layer 12 made of Pt (platinum) that is stacked in the z-axis direction on the domain wall motion layer 11.
- the domain wall motion layer 11 and the spin Hall layer 12 extend on the xy plane and have a predetermined width in the z-axis direction.
- the domain wall displacement layer 11 is a layer (antiferromagnetic layer) made of Mn 3 Ge, and detailed description of its physical properties is omitted since it is the same as that in (1A).
- spin Hall effect occurs, in which a flow of electron spins (spin current) occurs in the z-axis direction, which is perpendicular to the x-axis direction.
- Figure 8 shows a state in which electrons e1 and e2 with different spins move in opposite directions in the z-axis direction.
- electrons e1 spin-polarized in the negative y-axis direction are accumulated on the negative z-axis side of the spin Hall layer 12 (i.e., the lower side of the spin Hall layer 12 in Figure 8), while electrons e2 spin-polarized in the positive y-axis direction are accumulated on the positive z-axis side of the spin Hall layer 12 (i.e., the upper side of the spin Hall layer 12 in Figure 8).
- a spin current is generated in the spin Hall layer 12.
- SOT spin orbit torque
- This torque can cause the polarity of the magnetic octupole to be reversed. In other words, it becomes possible to write information to the magnetic octupole.
- the spin Hall layer 12 is made of Pt, but the spin Hall layer 12 is not limited to this and may be made of a material such as a non-magnetic metal or semiconductor that has strong spin-orbit interaction.
- non-magnetic metals include Pt (platinum), W (tungsten), and Ta (tantalum).
- the thickness of the domain wall displacement layer 11 (i.e., the width in the z-axis direction) may be on the order of tens to hundreds of nm, as shown in (1A).
- the thickness of the spin Hall layer 12 may be on the order of tens to tens of nm. The thinner the thickness of the spin Hall layer 12, the less current is required to generate the spin Hall effect, and the greater the energy saving effect. However, to ensure that the spin Hall effect is expressed in the spin Hall layer 12, it is preferable that the spin Hall layer 12 has at least the thickness (e.g., about 10 nm) required for spin-polarized electrons to accumulate on the top and bottom surfaces.
- the domain wall motion element can be configured to further include a domain wall motion layer 11 and a spin Hall layer 12 having at least one of Pt, Ta, and W stacked on the domain wall motion layer 11, which exhibits the spin Hall effect when a current is applied.
- a magnetization reversal can be generated at high speed in the domain wall motion layer 11 by passing a current through the spin Hall layer 12. Therefore, when the domain wall motion element T is used as a magnetic memory device, data can be written at high speed to the domain wall motion layer 11.
- the path of the current flowing through the domain wall motion layer 11 can be separated in the write and read operations of the magnetic memory device. Furthermore, there is no need to apply a magnetic field when reversing magnetization.
- Embodiment 2 Next, an application example of the domain wall motion element described in the first embodiment will be described.
- FIG. 9A is a schematic diagram of a memory device to which a domain wall motion element is applied.
- the memory device is mounted on an ASIC (Application Specific Integrated Circuit) 100, and includes a register section 101 and a data read line 102.
- ASIC Application Specific Integrated Circuit
- the register unit 101 writes spin information to the internal memory by a current.
- the internal memory is a thin wire composed of a layer of Mn 3 Ge, which is a non-collinear antiferromagnetic material, as shown in the first embodiment.
- a spin-orbit torque is applied from the register unit 101 to the magnetic octupole of the memory, causing magnetization reversal and writing data.
- the register unit 101 also moves a domain wall by passing a shift current through the memory, realizing another write in a new area of the memory and allowing the reading unit to read data. In this way, the register unit 101 has a function of shifting the magnetization information recorded as data, and is therefore also called a spin shift register.
- the magnetization information is read by the reading unit of the register unit 101 and then output from the data read line 102 as an electric signal.
- FIG. 9B is a detailed configuration diagram of the register unit 101.
- the register unit 101 includes a current generating unit 201 having a conductor 202, a spin Hall layer 203, a magnetoresistance element 204, and a memory line 301.
- FIG. 9C is a block diagram showing units related to the control of the register section 101.
- the ASIC 100 includes hardware configurations such as a control section 401, a current measurement circuit 402, and a data output circuit 403.
- the control unit 401 has a processor 411 and a memory 412.
- the processor 411 includes one or more processors such as a CPU (Central Processing Unit), an MPU (Micro Processing Unit), an FPGA (Field-Programmable Gate Array), a DSP (Digital Signal Processor), etc.
- Memory 412 is used to store one or more instructions.
- the one or more instructions are stored in memory 412 as a group of software modules (computer programs).
- Memory 412 is composed of volatile memory, non-volatile memory, or a combination of both.
- the number of memories 412 is not limited to one, and multiple memories 412 may be provided.
- the volatile memory may be, for example, RAM (Random Access Memory) such as DRAM (Dynamic Random Access Memory) or SRAM (Static Random Access Memory).
- the non-volatile memory may be, for example, PROM (Programmable ROM), EPROM (Erasable Programmable Read Only Memory), or Flash Memory.
- the processor 411 is connected to the memory 412, and can perform the following processing executed by the control unit 401 by reading and executing one or more instructions from the memory 412. Note that the memory 412 may be provided outside the processor 411, or may be built into the processor 411.
- the current measurement circuit 402 and the data output circuit 403 are any type of electrical circuit capable of performing the functions described below.
- the current generating unit 201 generates an electrical signal for writing information to the memory line 301 via the spin hole layer 203.
- the current generating unit 201 may have, for example, any photoelectric conversion element. In response to light input to the photoelectric conversion element, this photoelectric conversion element outputs a current, which is an electrical signal.
- the current generating unit 201 may have a circuit that generates an electrical signal by being controlled by the control unit 401.
- the conductor 202 of the current generating unit 201 is connected to the spin Hall layer 203, and both ends of the conductor 202 are connected to a power supply voltage and ground, respectively, so that a bias voltage V is applied.
- the conductor 202 passes a write current Iw corresponding to the electrical signal through the spin Hall layer 203.
- the spin Hall layer 203 overlaps (i.e., is stacked) with a portion of the memory line 301 perpendicularly, and has the same physical properties and functions as the spin Hall layer 12 described in (1B).
- a write current Iw flows through the spin Hall layer 203, a spin current is generated therein by the mechanism shown in (1B).
- the memory line 301 is a domain wall motion element having a domain wall motion layer made of a non-collinear antiferromagnetic material, and has the same physical properties and functions as the domain wall motion layer 11 shown in (1B). Therefore, when a spin orbit torque caused by a spin current is applied to the magnetic octupole of the memory line 301, magnetization reversal occurs, and data is written as magnetization information in the region of the memory line 301 stacked with the spin Hall layer 203. In this way, the current generation unit 201 and the spin Hall layer 203 determine the magnetization direction of the magnetic domain of the memory line 301, and function as a write unit that writes data to that magnetic domain.
- the magnetization information written is one bit of data, "0" or "1.”
- FIG. 9B if the magnetization information in the magnetic octupole is pointing upward (positive z-axis direction), it is defined as “0,” and if it is pointing downward (negative z-axis direction), it is defined as "1.”
- this magnetization information is separated from adjacent magnetization information by a domain wall.
- a shift current Is (pulse current) is passed through the memory line 301 in the x-axis direction along which the memory line 301 extends.
- a circuit for passing the shift current Is may be provided inside or outside the ASIC 100. This shift current Is causes the magnetization information to move in the x-axis direction within the memory line 301, as per the mechanism shown in (1A), to the position of the magnetoresistance element 204 separated from the spin Hall layer 203.
- the timing and duration of the shift current Is can be controlled as desired.
- FIG. 9D is a detailed configuration diagram of the magnetoresistance element 204.
- the magnetoresistance element 204 is a magnetic tunnel junction element (MTJ element), and has a memory area 301A that is a partial area of the memory line 301, a nonmagnetic layer 211, and a magnetization fixed layer 212.
- the memory area 301A, nonmagnetic layer 211, and magnetization fixed layer 212 are stacked in this order in the z-axis direction of FIG. 9B.
- magnetization M11 information As described above, in memory area 301A, one bit of data "0" or “1” is written to the magnetic octupole as magnetization M11 information.
- This magnetization M11 information is reversible, and is shown in FIG. 9D as arrows pointing in both directions.
- the magnetization information stored in memory area 301A changes when shift current Is flows.
- the non-magnetic layer 211 is made of an insulator such as MgO, and separates the memory area 301A from the magnetization fixed layer 212.
- the magnetization fixed layer 212 is a layer in which the direction of magnetization M12 is fixed, and is made of, for example, a ferromagnetic material or an antiferromagnetic material.
- the magnetization fixed layer 212 is made of either a single crystal or a polycrystal. Note that, although the explanation will continue assuming that magnetization M12 faces upward (positive direction of the z-axis) in FIG. 9D, magnetization M12 may also face downward (positive direction of the z-axis).
- the resistance of the magnetoresistance element 204 is in a low state. However, when the magnetization M11 and the magnetization M12 are in opposite directions (anti-parallel state), the resistance of the magnetoresistance element 204 is in a high state.
- a first terminal 221 is connected to the surface of the memory area 301A opposite to the surface on which the nonmagnetic layer 211 is laminated, and the drain of a transistor 222 is connected to the first terminal 221.
- the transistor 222 is, for example, an NMOS (N-channel metal oxide semiconductor) transistor, but may be another type of transistor.
- the gate of the transistor 222 is connected to the control unit 401 shown in FIG. 9C, and the control unit 401 controls the on and off of the transistor 222.
- a power supply voltage (not shown) is connected to the source of the transistor 222.
- a second terminal 223 is connected to the surface of the magnetization fixed layer 212 opposite to the surface on which the nonmagnetic layer 211 is laminated, and a read line 224 is connected to the second terminal 223.
- the read line 224 is connected to the current measurement circuit 402.
- the control unit 401 When the control unit 401 turns on the transistor 222, a predetermined voltage is applied to the magnetoresistance element 204. By applying a voltage to the magnetoresistance element 204 in this manner, the control unit 401 passes a read current from the first terminal 221 through the memory area 301A, the nonmagnetic layer 211, the magnetization fixed layer 212, and the second terminal 223 to the read line 224. At this time, even if the voltage value applied to the magnetoresistance element 204 is the same, the current value of the read current changes depending on whether the resistance of the magnetoresistance element 204 is high or low (i.e., depending on whether the magnetoresistance element 204 is in a parallel or anti-parallel state).
- the current measurement circuit 402 shown in FIG. 9C measures the current value of the read current and outputs the measurement value to the control unit 401.
- the control unit 401 uses the measurement value to determine whether the magnetoresistance element 204 is in a parallel or anti-parallel state.
- the control unit 401 determines whether the magnetoresistance element 204 is in a parallel or anti-parallel state, for example, by comparing the magnitude of a predetermined current threshold with the measurement value.
- the control unit 401 also obtains information on the direction of magnetization M12 of the magnetization fixed layer 212. This information is stored in, for example, the memory 412.
- the control unit 401 determines whether the information of the magnetization M11 of the memory area 301A indicates "0" or "1” based on the determination result indicating whether the magnetoresistance element 204 is in a parallel or anti-parallel state and the information on the direction of the magnetization M12.
- the control unit 401 controls the data output circuit 403 to output the determined result of "0" or "1” as an electrical signal from the data read line 102.
- the magnetoresistance element 204, the current measurement circuit 402, and the control unit 401 function as a reading unit that reads the magnetization information of the memory area 301A.
- a memory device serving as an ASIC 100 can be configured to include a memory line 301 having a domain wall motion layer made of a non-collinear antiferromagnetic material, a write unit that writes data into the magnetic domain by controlling the magnetization direction of the magnetic domain of the memory line 301, and a read unit that reads the magnetization direction of the magnetic domain that has moved in the memory line 301 by applying a current.
- the memory device exhibits the effects described in the first embodiment.
- the memory device may further include a photoelectric conversion element.
- the writing section of the memory device controls the magnetization direction of the magnetic domains using the electrical signal output by the photoelectric conversion element in response to the input light, and writes data to the magnetic domains. In this way, the memory device is capable of writing data in response to the input light.
- the present invention can also be considered as a data writing method having a first step of writing data to a magnetic domain in a magnetic domain wall displacement layer made of a non-collinear antiferromagnetic material by controlling the magnetization direction of the magnetic domain, and a second step of moving the magnetic domain in one direction in the magnetic domain wall displacement layer by applying a current to the magnetic domain wall displacement layer.
- the domain wall motion speed is maximized, and the effect of high-speed data writing can be improved as shown in the first embodiment.
- the domain wall motion speed is very fast compared to the domain wall motion speed in known materials.
- the material of the non-collinear antiferromagnetic material constituting the memory line 301 is not limited to Mn 3 Ge, and may be any of the various materials shown in the first embodiment.
- the ASIC 100 can be applied to any device.
- the ASIC 100 can be applied to optical communication devices.
- the input light to the photoelectric conversion element of the current generating unit 201 is, for example, any signal light output from a device other than the ASIC 100.
- the ASIC 100 can also be applied to other uses, in which case the input light may be light that is not output from the device, such as natural light.
- the current generating unit 201 is not essential to the ASIC 100.
- the ASIC 100 may obtain a write current output from a device other than the ASIC 100, and pass the write current directly or after performing any pre-processing to the spin hole layer 203, thereby writing data corresponding to the write current to the memory line 301.
- the hardware configuration shown in FIG. 9C is not limited to being inside the ASIC 100, but may be provided externally.
- the non-collinear antiferromagnetic material of the present invention may be configured so that distortion is introduced into the antiferromagnetic layer, ensuring that the degree of freedom of the polarization of the magnetic octupole is two-valued in the direction perpendicular to the film surface. This makes it easier to write and read digital data in a magnetic memory device.
- the memory device shown in the second embodiment is merely one example, and the domain wall motion element using a non-collinear antiferromagnetic material can be applied to other types of memory devices.
- the domain wall motion element may be applied to SOT-MRAM (Magnetoresistive Random Access Memory).
- each of the plurality of memory cells is connected to a bit line and a word line for writing and reading data.
- Each memory cell has an MTJ element.
- this MTJ element is formed by sequentially stacking a memory area 301A using a non-collinear antiferromagnetic material, a non-magnetic layer 211, and a magnetization fixed layer 212.
- the memory area 301A is not configured as a fine line, but is provided individually for each MTJ element (i.e., separated for each MTJ element).
- a spin-hole layer connected to a bit line and a word line is stacked on the surface formed on the opposite side of the non-magnetic layer 211 in the memory area 301A.
- a first transistor connected to the spin-hole layer at the drain is connected to the first bit line at its source and to the word line at its gate.
- a second transistor connected to the spin-hole layer at the drain is connected to the second bit line at its source and to the word line common to the first transistor at its gate.
- Other aspects of the MTJ element configuration are similar to the magnetoresistance element 204 in embodiment 2, so the description will be omitted.
- the control unit 401 controls the voltage levels on the bit lines and word lines to perform writing.
- the control unit 401 sets the voltage level on the word lines to the H level, and sets the voltage level on one of the first bit line and the second bit line to the H level and the voltage level on the other to the L level.
- the control unit 401 controls the voltage levels of each bit line and word line, thereby storing different digital information in each of the multiple memory cells arranged in a matrix.
- the control unit 401 also sets the voltage level of the word line to the H level, and sets the voltage level of one of the first bit line and the second bit line to the H level and leaves the other in an open state, thereby passing a read current through the memory cell and reading data. Details of this data reading are as described in the second embodiment, and therefore will not be described here.
- a domain wall motion element is provided with an antiferromagnetic layer made of an antiferromagnetic material having a non-collinear spin structure, the antiferromagnetic layer having a domain wall that moves in one direction when a current is applied thereto.
- the antiferromagnetic material is any one of Mn 3 Ge, Mn 3 Sn, Mn 3 Ga, Mn 3 Rh, Mn 3 Pt, and Mn 3 Ir. 2.
- the antiferromagnetic material has a kagome lattice as a crystal structure, The one direction in which the domain wall moves is a direction substantially perpendicular to a normal vector of a plane formed by the Kagome lattice. 3.
- the domain wall motion element according to claim 1 or 2. (Appendix 4)
- the antiferromagnetic layer is made of a single crystal. 4.
- the domain wall motion element according to claim 1 . (Appendix 5)
- a spin Hall layer is further provided on the antiferromagnetic layer, the spin Hall layer having at least one of Pt, Ta, and W, and exhibiting a spin Hall effect when a current is applied thereto. 5.
- the domain wall motion element according to claim 1 is
- (Appendix 6) a domain wall motion element having an antiferromagnetic layer made of an antiferromagnetic material having a non-collinear spin structure; a writing unit that writes data into the magnetic domains by determining the magnetization direction of the magnetic domains of the antiferromagnetic layer; a reading unit that reads the magnetization direction of the magnetic domain that has moved in the domain wall motion element by applying a current to the antiferromagnetic layer;
- a memory device comprising: (Appendix 7) the writing unit has a photoelectric conversion element that outputs an electrical signal according to input light, and controls the magnetization direction of the magnetic domain using the electrical signal output by the photoelectric conversion element to write data in the magnetic domain. 7. The memory device of claim 6.
- (Appendix 8) a first step of writing data to a magnetic domain by controlling the magnetization direction of the magnetic domain of an antiferromagnetic layer made of an antiferromagnetic material having a non-collinear spin structure; a second step of applying a current to the antiferromagnetic layer to move the magnetic domain in one direction across the antiferromagnetic layer;
- the data writing method includes the steps of: (Appendix 9) Repeating the first and second steps a number of times; 9.
- M antiferromagnetic layer
- F ferromagnetic layer
- T domain wall motion element 11: domain wall motion layer 12: spin Hall layer 100: ASIC 101
- Register section 102 Data read line 201 Current generating section 202 Conductor 203 Spin Hall layer 204 Magnetoresistance element 211 Nonmagnetic layer 212 Magnetization fixed layer 221 First terminal 222 Transistor 223 Second terminal 224 Read line 301 Memory line 301A Storage area 401 Control section 402 Current measuring circuit 403 Data output circuit 411 Processor 412 Memory
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Abstract
According to the present disclosure, it is possible to achieve a magnetic domain wall moving element capable of improving a magnetic domain wall moving speed. A magnetic domain wall moving element according to one embodiment of the present disclosure comprises an antiferromagnetic layer that is made of an antiferromagnetic material having a non-collinear spin structure, and has a magnetic domain wall that moves in one direction by application of current.
Description
本発明は、磁壁移動素子、メモリデバイス及びデータ書込み方法に関する。
The present invention relates to a domain wall motion element, a memory device, and a data writing method.
コンピュータ等に搭載される磁気メモリデバイスは、そのパフォーマンスの向上が課題となっており、そのための研究開発がなされている。
Improving the performance of magnetic memory devices installed in computers and other devices is a challenge, and research and development is being conducted to achieve this.
例えば、特許文献1には、それぞれの磁化方向が互いに逆向きに固定された第1及び第2のピニング層の両方と磁気的に結合するように磁化自由層を形成し、磁化方向を第1方向あるいは第2方向に設定する磁壁移動領域が磁化自由層内に形成されるような、磁壁移動素子の製造方法が記載されている。磁壁移動素子をこのようにして製造することにより、磁壁移動により磁化状態が変化する磁壁移動素子の初期化を行うことが意図されている。
For example, Patent Document 1 describes a method for manufacturing a domain wall motion element in which a magnetization free layer is formed so as to be magnetically coupled with both a first and a second pinning layer whose magnetization directions are fixed in opposite directions, and a domain wall motion region in which the magnetization direction is set to the first direction or the second direction is formed in the magnetization free layer. By manufacturing the domain wall motion element in this manner, it is intended to initialize the domain wall motion element whose magnetization state changes due to domain wall motion.
不揮発性メモリとしての磁気メモリデバイスは、電力が供給されない状態で内部データを保持することができるため、省エネの効果が大きい。このような磁気メモリデバイスには、強磁性体が用いられ、その磁極情報(垂直2値状態の情報)が、デジタル情報として内部に記録されていた。しかしながら、強磁性体を用いた磁気メモリデバイスは、その磁壁移動速度が限られているため、動作速度の向上に限界があった。特許文献1に記載の技術は、磁壁移動素子の初期化に関するものであり、このような課題を解決するものではなかった。
Magnetic memory devices as non-volatile memories are able to retain internal data even when power is not being supplied, which is a great energy-saving effect. Such magnetic memory devices use ferromagnetic materials, and the magnetic pole information (information on the perpendicular binary state) is recorded internally as digital information. However, magnetic memory devices using ferromagnetic materials have a limited domain wall motion speed, so there is a limit to how much the operating speed can be improved. The technology described in Patent Document 1 is related to the initialization of domain wall motion elements, and does not solve these problems.
本発明は、このような問題点に鑑みてなされたものであり、磁壁移動速度を向上させることが可能な磁壁移動素子、メモリデバイス及びデータ書込み方法を実現する。
The present invention was made in consideration of these problems, and realizes a domain wall motion element, memory device, and data writing method that can improve the domain wall motion speed.
本発明の一態様に係る磁壁移動素子は、非共線性のスピン構造を有する反強磁性体からなり、電流が印加されることによって一方向に移動する磁壁を有する反強磁性層を備える。
The domain wall motion element according to one embodiment of the present invention is made of an antiferromagnetic material having a non-collinear spin structure, and is provided with an antiferromagnetic layer having a domain wall that moves in one direction when a current is applied.
上記磁壁移動素子において、前記反強磁性体は、Mn3Ge、Mn3Sn、Mn3Ga、Mn3Rh、Mn3Pt、又はMn3Irのいずれかであってもよい。
In the above domain wall motion element, the antiferromagnetic material may be any one of Mn3Ge , Mn3Sn , Mn3Ga , Mn3Rh , Mn3Pt , and Mn3Ir .
上記磁壁移動素子において、前記反強磁性体は、結晶構造としてカゴメ格子を有し、前記磁壁が移動する前記一方向は、前記カゴメ格子が形成する平面の法線ベクトルと略垂直な方向であってもよい。
In the above domain wall motion element, the antiferromagnetic material may have a kagome lattice as a crystal structure, and the one direction in which the domain wall moves may be a direction approximately perpendicular to the normal vector of the plane formed by the kagome lattice.
上記磁壁移動素子において、前記反強磁性層は単結晶で構成されてもよい。
In the domain wall motion element, the antiferromagnetic layer may be made of a single crystal.
上記磁壁移動素子は、前記反強磁性層に積層された、Pt、Ta、Wの少なくともいずれかを有し、電流が印加されることによってスピンホール効果を発現するスピンホール層をさらに備えてもよい。
The domain wall motion element may further include a spin Hall layer that contains at least one of Pt, Ta, and W and is stacked on the antiferromagnetic layer, and that exhibits the spin Hall effect when a current is applied.
本発明の一態様に係るメモリデバイスは、非共線性のスピン構造を有する反強磁性体からなる反強磁性層を有する磁壁移動素子と、前記反強磁性層の磁区の磁化方向を定めることで、前記磁区にデータを書き込む書込み部と、電流が前記反強磁性層に印加されることによって前記磁壁移動素子内で移動した前記磁区の磁化方向を読み取る読み取り部を備える。
A memory device according to one embodiment of the present invention includes a domain wall motion element having an antiferromagnetic layer made of an antiferromagnetic material having a non-collinear spin structure, a write unit that writes data into the magnetic domain by determining the magnetization direction of the magnetic domain in the antiferromagnetic layer, and a read unit that reads the magnetization direction of the magnetic domain that has moved within the domain wall motion element by applying a current to the antiferromagnetic layer.
上記書込み部は、入力光に応じた電気信号を出力する光電変換素子を有し、前記光電変換素子が出力した電気信号を用いて前記磁区の磁化方向を制御し、前記磁区にデータを書き込んでもよい。
The writing unit may have a photoelectric conversion element that outputs an electrical signal according to input light, and may use the electrical signal output by the photoelectric conversion element to control the magnetization direction of the magnetic domain and write data to the magnetic domain.
本発明の一態様に係るデータ書込み方法は、非共線性のスピン構造を有する反強磁性体からなる反強磁性層の磁区の磁化方向を制御することで、前記磁区にデータを書き込む第1のステップと、前記反強磁性層に電流を印加することで、前記反強磁性層の一方向に前記磁区を移動させる第2のステップを有する。
A data writing method according to one aspect of the present invention includes a first step of writing data to a magnetic domain by controlling the magnetization direction of the magnetic domain of an antiferromagnetic layer made of an antiferromagnetic material having a non-collinear spin structure, and a second step of moving the magnetic domain in one direction of the antiferromagnetic layer by applying a current to the antiferromagnetic layer.
上記データ書込み方法では、前記第1及び第2のステップが複数回繰り返し実行されてもよい。
In the above data writing method, the first and second steps may be repeated multiple times.
本発明によれば、磁壁移動速度を向上させることが可能な磁壁移動素子、メモリデバイス及びデータ書込み方法を実現することができる。
The present invention makes it possible to realize a domain wall motion element, a memory device, and a data writing method that can improve the domain wall motion speed.
以下、図面を参照して、本発明の実施の形態について説明する。なお、発明を実施するための形態における以下の記載及び図面は、説明の明確化のため、適宜、省略及び簡略化がなされている。また、説明を明確にするため、素子又はデバイスの構造については、適宜、3次元座標系を用いた説明がなされる。さらに、数値範囲を示す「-」は特に断りがない限り、その下限値及び上限値を含むものとする。また、この開示では、明記のない限り、複数の項目について「その少なくともいずれか」が定義された場合、その定義は、任意の1つの項目を意味しても良いし、任意の複数の項目(全ての項目を含む)を意味しても良い。
Below, an embodiment of the present invention will be described with reference to the drawings. Note that the following description and drawings in the embodiment of the invention have been omitted or simplified as appropriate for clarity of explanation. Also, for clarity of explanation, the structure of the element or device will be explained using a three-dimensional coordinate system as appropriate. Furthermore, unless otherwise specified, a "-" indicating a numerical range includes the lower limit and upper limit. Also, in this disclosure, unless otherwise specified, when "at least any of" multiple items is defined, the definition may mean any one item, or any multiple items (including all items).
実施の形態1
(1A)
図1は、磁壁移動素子の要素である、非共線性のスピン構造を有する反強磁性体(以下、非共線反強磁性体とも記載する)であるMn3Geの磁気構造を示す図である。Mn3Geは、c軸方向に磁性原子のMn(マンガン)からなるカゴメ格子が積層した結晶構造を有するものであり、図1では、そのカゴメ格子の一層のカゴメ面における磁気構造が示されている。 First embodiment
(1A)
1 is a diagram showing the magnetic structure of Mn 3 Ge, an antiferromagnetic material having a non-collinear spin structure (hereinafter also referred to as a non-collinear antiferromagnetic material), which is an element of a domain wall motion element. Mn 3 Ge has a crystal structure in which kagome lattices made of magnetic atoms Mn (manganese) are stacked in the c-axis direction, and FIG. 1 shows the magnetic structure of one kagome plane of the kagome lattice.
(1A)
図1は、磁壁移動素子の要素である、非共線性のスピン構造を有する反強磁性体(以下、非共線反強磁性体とも記載する)であるMn3Geの磁気構造を示す図である。Mn3Geは、c軸方向に磁性原子のMn(マンガン)からなるカゴメ格子が積層した結晶構造を有するものであり、図1では、そのカゴメ格子の一層のカゴメ面における磁気構造が示されている。 First embodiment
(1A)
1 is a diagram showing the magnetic structure of Mn 3 Ge, an antiferromagnetic material having a non-collinear spin structure (hereinafter also referred to as a non-collinear antiferromagnetic material), which is an element of a domain wall motion element. Mn 3 Ge has a crystal structure in which kagome lattices made of magnetic atoms Mn (manganese) are stacked in the c-axis direction, and FIG. 1 shows the magnetic structure of one kagome plane of the kagome lattice.
図1において、カゴメ面Kの外側ではGe(ゲルマニウム)が六角形の構造を形成し、内側ではMnが六角形の構造を形成している。図1では、Mn原子の各々のスピンの向きが矢印で示されている。なお、図2以降においてMn3Geのカゴメ面を示す図においても、同様に、Mn原子の各々のスピンの向きが矢印で示される。
In Fig. 1, Ge (germanium) forms a hexagonal structure on the outside of the kagome surface K, and Mn forms a hexagonal structure on the inside. In Fig. 1, the direction of the spin of each Mn atom is indicated by an arrow. Note that in Fig. 2 and subsequent figures showing the kagome surface of Mn 3 Ge, the direction of the spin of each Mn atom is similarly indicated by an arrow.
図1(A)では、隣接したMn原子同士のスピンは、互いに120度ずれている。この構造は、逆120度構造と呼ばれるものであり、Mn3Geは、反強磁性秩序(又は、カイラル反強磁性秩序)状態にある。このとき、六角形全体におけるMnのスピンは、弱い強磁性モーメントを呈しており、磁気八極子とも称され、Mn3Geの微小磁化方向を決定する。磁気八極子は、図1(A)において下向きの矢印として示した磁化方向H1となる。
In Fig. 1(A), the spins of adjacent Mn atoms are offset by 120 degrees from each other. This structure is called an inverted 120-degree structure, and Mn 3 Ge is in an antiferromagnetic order (or chiral antiferromagnetic order). In this case, the Mn spins in the entire hexagon exhibit a weak ferromagnetic moment, also called a magnetic octupole, which determines the micromagnetization direction of Mn 3 Ge. The magnetic octupole has a magnetization direction H1 shown as a downward arrow in Fig. 1(A).
他方、図1右側の(B)において、カゴメ面内部においてMnが構成する六角形の構造でも、隣接したMn原子同士のスピンは、互いに120度ずれている。しかしながら、各Mn原子は、図1(A)とは異なる方向のスピンを有している。そのため、図1(B)において、Mn3Geは反強磁性秩序状態にあるものの、その磁気八極子は、図1(B)において上向きの矢印として示した磁化方向H2となる。
On the other hand, in the hexagonal structure formed by Mn inside the kagome plane in the right side of Fig. 1B, the spins of adjacent Mn atoms are also shifted by 120 degrees from each other. However, each Mn atom has a spin in a different direction from that in Fig. 1A. Therefore, although Mn 3 Ge is in an antiferromagnetic order in Fig. 1B, its magnetic octupole has a magnetization direction H2 shown by an upward arrow in Fig. 1B.
以上に示したように、図1(A)と(B)では、磁気八極子の向きが反対になる。そして、Mn3Geにおける磁気八極子の偏極状態を制御することで、図1(A)と(B)の状態を互いに切り替えることができるため、非共線反強磁性体は、「0」又は「1」の状態を記録するメモリとしても用いることができる。この詳細については後述する。なお、このような微小な磁化を有する反強磁性体は、キャントした反強磁性体(canted antiferromagnet)とも呼ばれる。
As described above, the orientation of the magnetic octopole is opposite in Fig. 1(A) and (B). By controlling the polarization state of the magnetic octopole in Mn 3 Ge, the state of Fig. 1(A) and (B) can be switched between each other, so that the non-collinear antiferromagnet can also be used as a memory that records the state of "0" or "1". The details will be described later. An antiferromagnet with such a minute magnetization is also called a canted antiferromagnet.
図2は、Mn3Geの異常ホール効果を示す図である。図2に示した通り、Mn3Geのカゴメ面は、Mn3Geの層M(反強磁性層)の平面方向である[0001]方向に垂直となるように積層されている。ここで、図1において説明した通り、Mn3Geでは磁気八極子による偏極があるため、反強磁性層Mにおいて[01-10]方向に大きな仮想磁場Hが生じる。
Fig. 2 is a diagram showing the anomalous Hall effect of Mn 3 Ge. As shown in Fig. 2, the kagome planes of Mn 3 Ge are stacked so as to be perpendicular to the [0001] direction, which is the planar direction of the Mn 3 Ge layer M (antiferromagnetic layer). As explained in Fig. 1, Mn 3 Ge is polarized by magnetic octopoles, so a large virtual magnetic field H is generated in the [01-10] direction in the antiferromagnetic layer M.
この状態において、反強磁性層Mの[0001]方向に電流iが流される。このとき、反強磁性層Mに磁場が印加されていないにもかかわらず、仮想磁場Hによって、反強磁性層M内の電子eは、反強磁性層Mの平面方向である[2-1-10]方向にその移動方向が曲げられる。このようにして、[2-1-10]方向にホール電圧が生じる、異常ホール効果が発生する。
In this state, a current i is passed in the [0001] direction of the antiferromagnetic layer M. At this time, even though no magnetic field is applied to the antiferromagnetic layer M, the virtual magnetic field H causes the direction of movement of the electrons e in the antiferromagnetic layer M to bend toward the [2-1-10] direction, which is the planar direction of the antiferromagnetic layer M. In this way, a Hall voltage is generated in the [2-1-10] direction, and the anomalous Hall effect occurs.
図3A~3Cは、Mn3Geの細線における磁壁移動の状況を示す。まず、図3Aを用いて、Mn3Geの細線における磁壁移動の手法について説明する。
3A to 3C show the state of domain wall motion in a thin wire of Mn 3 Ge. First, a method of domain wall motion in a thin wire of Mn 3 Ge will be described with reference to FIG.
図3Aにおいて、Mn3Geの細線Nは、[2-1-10]方向に延びた形状を有する。この細線Nに対し、[2-1-10]方向と直交する[0001]方向に書込み電流Cを流すことにより、両端に磁壁を有する磁区D1を生成する。この磁壁はネール磁壁(Neel wall)である。そして、パルス幅がナノ秒のオーダーとなるパルス電流tを細線Nにおける[2-1-10]の負の方向に流すことにより、磁区D1は、図3Aで示した磁区D2の位置まで移動する。このパルス電流tは、シフト電流とも呼ばれる。
In FIG. 3A, the Mn 3 Ge thin wire N has a shape extending in the [2-1-10] direction. By passing a write current C through this thin wire N in the [0001] direction perpendicular to the [2-1-10] direction, a magnetic domain D1 having magnetic domain walls at both ends is generated. This magnetic domain wall is a Neel wall. Then, by passing a pulse current t having a pulse width on the order of nanoseconds through the thin wire N in the negative direction of [2-1-10], the magnetic domain D1 moves to the position of the magnetic domain D2 shown in FIG. 3A. This pulse current t is also called a shift current.
なお、パルス電流tが流れる方向は、図3Aにおいて左向きの方向を正の値とし、磁壁の移動距離xの方向は、図3Aにおいて右向きの方向(つまり、磁区D1からD2に向かう方向)を正の値とする。
Note that the direction in which the pulse current t flows is taken to be positive in the leftward direction in FIG. 3A, and the direction in which the domain wall moves x is taken to be positive in the rightward direction in FIG. 3A (i.e., the direction from magnetic domain D1 to D2).
図3Bは、Mn3Geの磁壁移動を時系列によって示す図である。まず、時刻t1においては、書込み電流Cによって、細線N内に磁区(磁壁)が生成される状態が示されている。次に、時刻t1から時系列が後となる時刻t2では、パルス電流tによって、磁区が正の方向に移動している。さらに、時刻t2から時系列が後となる時刻t3では、パルス電流tによって、磁区がさらに正の方向に移動している。
3B is a diagram showing the magnetic domain wall movement of Mn 3 Ge in a time series. First, at time t1, a state in which a magnetic domain (magnetic domain wall) is generated in the thin wire N by the write current C is shown. Next, at time t2, which is later in the time series than time t1, the magnetic domain moves in the positive direction by the pulse current t. Furthermore, at time t3, which is later in the time series than time t2, the magnetic domain moves further in the positive direction by the pulse current t.
図3Cは、Mn3Geの磁壁移動の状態を示すグラフである。図3Cにおいて三角のドットで示されるデータは、磁区の移動距離xの方向及びパルス電流tが流れる方向が正である場合のデータを示し、丸のドットで示されるデータは、磁区の移動距離xの方向及びパルス電流tが流れる方向が負である場合のデータを示す。図3Cのグラフの横軸は、細線N内におけるパルス電流の電流密度jを示したものであり、縦軸は、磁壁の移動速度Vを示す。図3Cでは、電流密度jの絶対値がおよそ4*1010(A/m2)以上となったときに、磁壁が一定速度以上で移動することが示される。
Fig. 3C is a graph showing the state of domain wall movement in Mn3Ge . In Fig. 3C, data shown by triangular dots indicates data when the direction of the magnetic domain movement distance x and the direction of the pulse current t are positive, and data shown by circular dots indicates data when the direction of the magnetic domain movement distance x and the direction of the pulse current t are negative. The horizontal axis of the graph in Fig. 3C indicates the current density j of the pulse current in the fine wire N, and the vertical axis indicates the domain wall movement speed V. Fig. 3C shows that when the absolute value of the current density j is approximately 4* 1010 (A/ m2 ) or more, the domain wall moves at a constant speed or more.
以上に示した通り、Mn3Geの細線は、磁壁移動素子として用いることが可能となる。また、以下において、Mn3Geにおける磁壁移動のメカニズムについてさらに説明する。
As described above, the Mn 3 Ge thin wire can be used as a domain wall motion element. The mechanism of domain wall motion in Mn 3 Ge will be further explained below.
図4Aは、Mn3Geのカゴメ面に対して、磁壁を移動させるためのシフト電流jが流れるときの状態を示す図である。カゴメ面Kは、xy平面上に位置しており、カゴメ面Kの法線方向としてz軸方向が定義される。ここで、x軸方向は[2-1-10]方向であり、y軸方向は[01-10]方向であり、z軸方向は[0001]方向である。そして、シフト電流jのベクトルがz軸となす角度をφと定義する。なお、Mn3Geにおける磁壁は、図3A~図3Cに示した通り、シフト電流jのベクトルの方向と反対の方向に移動する。
4A is a diagram showing a state when a shift current j flows through the kagome surface of Mn 3 Ge to move the domain wall. The kagome surface K is located on the xy plane, and the z-axis direction is defined as the normal direction of the kagome surface K. Here, the x-axis direction is the [2-1-10] direction, the y-axis direction is the [01-10] direction, and the z-axis direction is the [0001] direction. The angle that the vector of the shift current j makes with the z-axis is defined as φ. Note that the domain wall in Mn 3 Ge moves in the opposite direction to the vector direction of the shift current j, as shown in FIGS. 3A to 3C.
図4Bは、φが0°、45°、60°、90°の場合における、Mn3Geの磁壁移動の状態を示すグラフである。図4Bのグラフの横軸は、シフト電流の電流密度jの絶対値を示したものであり、縦軸は、磁壁の移動速度Vを示す。
Fig. 4B is a graph showing the state of domain wall motion in Mn3Ge when φ is 0°, 45°, 60°, and 90°. The horizontal axis of the graph in Fig. 4B indicates the absolute value of the current density j of the shift current, and the vertical axis indicates the domain wall motion speed V.
図4Cは、φ=90°及びφ=0°の場合の、シフト電流とカゴメ面との位置関係を示す図である。φ=90°では、シフト電流jのベクトルは、カゴメ面Kの平面に平行となる。換言すれば、シフト電流jは、カゴメ面の平面内を流れることを意味する。この場合、シフト電流jに関するMn3Geのスピン偏極は0ではない値になる。また、移動する磁壁はネール磁壁である。一方、φ=0°では、シフト電流jのベクトルは、カゴメ面Kの平面に垂直となる。この場合、シフト電流jに関するMn3Geのスピン偏極は、φ=90°と比較すると微小な値(例えば、φ=90°のスピン偏極の1/10程度の値)となる。また、移動する磁壁はブロッホ磁壁(Bloch wall)である。
FIG. 4C is a diagram showing the positional relationship between the shift current and the kagome surface when φ=90° and φ=0°. When φ=90°, the vector of the shift current j is parallel to the plane of the kagome surface K. In other words, the shift current j flows within the plane of the kagome surface. In this case, the spin polarization of Mn 3 Ge related to the shift current j is a non-zero value. The moving domain wall is a Neel domain wall. On the other hand, when φ=0°, the vector of the shift current j is perpendicular to the plane of the kagome surface K. In this case, the spin polarization of Mn 3 Ge related to the shift current j is a small value compared to φ=90° (for example, about 1/10 of the spin polarization at φ=90°). The moving domain wall is a Bloch wall.
図4Bでは、任意のφの値について、図3Cで説明した通り、シフト電流jの絶対値が大きくなるほど、移動速度Vが増加することが示されている。また、図4Bには、φの値が0°から増加するにつれて磁壁の移動速度Vが増加し、φ=90°において移動速度Vが最大となることも示されている。ただし、φ=0°の場合でも、磁壁は移動することが可能となる。例えば、シフト電流の電流密度jの絶対値が6*1010(A/m2)の場合にVが略100(m/s)となり、電流密度jの絶対値が8*1010(A/m2)の場合にVが略200(m/s)となる。この移動速度は、公知の他の種類の材料における磁壁の移動速度と比較すると、非常に速いものとなる。
In Fig. 4B, for any value of φ, as explained in Fig. 3C, it is shown that the larger the absolute value of the shift current j, the greater the movement speed V. Fig. 4B also shows that as the value of φ increases from 0°, the movement speed V of the domain wall increases, and the movement speed V is maximum at φ=90°. However, even when φ=0°, the domain wall can move. For example, when the absolute value of the current density j of the shift current is 6*10 10 (A/m 2 ), V is approximately 100 (m/s), and when the absolute value of the current density j is 8*10 10 (A/m 2 ), V is approximately 200 (m/s). This movement speed is very fast compared to the movement speed of the domain wall in other known types of materials.
図5は、強磁性体における磁壁移動のメカニズムを示す図である。図5において、矢印は強磁性層F内の自発磁化(磁気モーメント)の向きを示す。(I)においては、磁気モーメントの向きが強磁性層Fの中央において変化しており、この箇所が磁壁になる。また、磁壁を挟んで、強磁性層Fの右側と左側とは異なる磁区となる。
Figure 5 shows the mechanism of domain wall movement in a ferromagnetic material. In Figure 5, the arrows indicate the direction of spontaneous magnetization (magnetic moment) in the ferromagnetic layer F. In (I), the direction of the magnetic moment changes in the center of the ferromagnetic layer F, and this location becomes a domain wall. In addition, the right and left sides of the ferromagnetic layer F on either side of the domain wall form different magnetic domains.
(II)では、(I)に示した状態から、図5の左側に向けてシフト電流が流れる状態を示す。磁壁をシフト電流が通過する際に、電子のスピンが磁気モーメントと相互作用することにより、電子のスピン角運動量が磁気モーメントに受け渡される。これにより、磁気モーメントが回転して、磁壁が図5の右側に向けて移動することになる。このスピン角運動量の受け渡しのメカニズムは、スピントランスファートルクとも称される。
(II) shows the state in which a shift current flows from the state shown in (I) to the left side of Figure 5. When the shift current passes through the domain wall, the electron spin interacts with the magnetic moment, transferring the electron spin angular momentum to the magnetic moment. This causes the magnetic moment to rotate, and the domain wall to move to the right side of Figure 5. This mechanism of transferring spin angular momentum is also called spin transfer torque.
(III)は、磁気モーメントが回転した結果、(II)と比較して、磁壁が図5の右側に向けて移動した状態を示す。このような強磁性体における磁壁の移動速度をuとすると、uは以下の式で表される。
u∝(J・P)/Ms ・・・(1)
ここで、Jはシフト電流の電流密度であり、Pは強磁性体のスピン分極率であり、Msは磁化の大きさを意味する。 (III) shows a state in which the magnetic moment has rotated, and as a result, the magnetic domain wall has moved toward the right side of Fig. 5 compared to (II). If the moving speed of the magnetic domain wall in such a ferromagnetic material is u, then u can be expressed by the following equation.
u ∝ (J P) / Ms ... (1)
Here, J is the current density of the shift current, P is the spin polarization of the ferromagnetic material, and Ms is the magnitude of magnetization.
u∝(J・P)/Ms ・・・(1)
ここで、Jはシフト電流の電流密度であり、Pは強磁性体のスピン分極率であり、Msは磁化の大きさを意味する。 (III) shows a state in which the magnetic moment has rotated, and as a result, the magnetic domain wall has moved toward the right side of Fig. 5 compared to (II). If the moving speed of the magnetic domain wall in such a ferromagnetic material is u, then u can be expressed by the following equation.
u ∝ (J P) / Ms ... (1)
Here, J is the current density of the shift current, P is the spin polarization of the ferromagnetic material, and Ms is the magnitude of magnetization.
スピン分極率Pは、強磁性体のスピン偏極と相関関係があり、強磁性体のスピン偏極が大きくなった場合、スピン分極率Pも大きくなるため、uが大きい値となる。つまり、磁壁がより高速で移動することになる。一方、強磁性体のスピン偏極が0となった場合、スピン分極率Pが0となるため、uが0となる。つまり、強磁性体において、磁壁は移動しない。以上から、強磁性体においては、スピン偏極の程度が、磁壁移動の重要なファクターといえる。
Spin polarization P is correlated with the spin polarization of a ferromagnetic material. When the spin polarization of a ferromagnetic material increases, the spin polarization P also increases, and so u becomes a larger value. In other words, the domain wall moves faster. On the other hand, when the spin polarization of a ferromagnetic material becomes 0, the spin polarization P also becomes 0, and so u becomes 0. In other words, the domain wall does not move in a ferromagnetic material. From the above, it can be said that the degree of spin polarization is an important factor in domain wall movement in a ferromagnetic material.
しかしながら、非共線反強磁性体であるMn3Geの場合、上記の通り、シフト電流jに関するMn3Geのスピン偏極がφ=90°と比較すると微小な値となるφ=0°の場合でも、Mn3Ge内の磁壁は移動することができる。そのため、非共線反強磁性体において、スピン偏極は、磁壁移動の要因となるものではないと考えられる。
However, in the case of Mn 3 Ge, which is a non-collinear antiferromagnetic material, as described above, even when φ=0°, where the spin polarization of Mn 3 Ge with respect to the shift current j is a small value compared to φ=90°, the domain wall in Mn 3 Ge can move. Therefore, in a non-collinear antiferromagnetic material, the spin polarization is not considered to be a factor in the domain wall movement.
図6Aは、強磁性体における磁壁移動の詳細なメカニズムを示す図である。図6Aは、自発磁化σを有する強磁性体に対して電流jが流された場合に、強磁性体内の磁気モーメントが、図5にて説明した電子のスピン角運動量由来のトルクτsttを受けて回転する状態を示している。ここで、電流jはx軸の正の方向に流れ、磁壁はx軸の負の方向に移動する。
Fig. 6A is a diagram showing a detailed mechanism of domain wall movement in a ferromagnetic material. Fig. 6A shows a state in which, when a current j flows through a ferromagnetic material having spontaneous magnetization σ, the magnetic moment in the ferromagnetic material rotates under the torque τ stt derived from the spin angular momentum of electrons described in Fig. 5. Here, the current j flows in the positive direction of the x-axis, and the domain wall moves in the negative direction of the x-axis.
図6Bは、Mn3Geにおける磁壁移動の詳細なメカニズムを示す図である。図6Bは、自発磁化σを有するMn3Geに対して電流jが流された場合に、Mn3Geの磁気八極子がトルクτeffを受けて回転する状態を示している。
Fig. 6B is a diagram showing a detailed mechanism of domain wall motion in Mn 3 Ge, in which when a current j is applied to Mn 3 Ge having a spontaneous magnetization σ, a magnetic octupole of Mn 3 Ge receives a torque τ eff and rotates.
局所的に磁化方向が変化する磁壁の領域に電流を流すと、磁壁近傍において、電場により非平衡スピン蓄積が誘起されることが知られている。図6Bに示したMn3Geにおける磁壁移動は、スピン偏極ではなく、この非平衡スピン蓄積によって磁気八極子にトルクが与えられることで生じる。したがって、スピン偏極度が小さく、磁壁移動には適していないと考えられてきた磁性材料においても、非平衡スピン蓄積を用いることで、高速に磁壁を動かせる可能性がある。
It is known that when a current is passed through a domain wall region where the magnetization direction changes locally, a non-equilibrium spin accumulation is induced by the electric field near the domain wall. The domain wall motion in Mn 3 Ge shown in Figure 6B is caused not by spin polarization but by the torque applied to the magnetic octupole by this non-equilibrium spin accumulation. Therefore, even in magnetic materials that have been thought to be unsuitable for domain wall motion due to their small spin polarization, it is possible to move the domain wall at high speed by using non-equilibrium spin accumulation.
図6Cは、Mn3Geにおける、磁壁の幅Lと、単位電場あたりのスピン蓄積量Saとの関係を示すグラフである。図6Cでは、ネール磁壁とブロッホ磁壁の両方についてグラフが示されている。図6Cから参照される通り、ネール磁壁とブロッホ磁壁の両方とも、磁壁の幅Lが小さくなるほど、単位電場あたりのスピン蓄積量Saの絶対値が増加する。単位電場あたりのスピン蓄積量Saの絶対値の増加に伴い、上述のトルクτeffが増加し、磁壁がより高速に動かせることになる。
Fig. 6C is a graph showing the relationship between the domain wall width L and the spin accumulation amount Sa per unit electric field in Mn 3 Ge. In Fig. 6C, graphs are shown for both the Neel domain wall and the Bloch domain wall. As can be seen from Fig. 6C, for both the Neel domain wall and the Bloch domain wall, the absolute value of the spin accumulation amount Sa per unit electric field increases as the domain wall width L decreases. As the absolute value of the spin accumulation amount Sa per unit electric field increases, the torque τ eff described above increases, and the domain wall can be moved at a higher speed.
図7は、様々な材料を磁壁移動素子として実験で用いた場合の磁壁速度を示したグラフである。図7のグラフの縦軸は、規格化された電流密度における磁壁移動速度Vを示す。図7には、反強磁性体(AntiFerromagnetic material:AFM)であるMn3Ge、フェリ磁性体(Ferrimagnetic material:FI)であるPt/BiYIG/GSGG、Mn4-xNixN、GdCo/Pt、合成反強磁性体(Synthetic AntiFerromagnetic material:SAF)であるSAF1、SAF2、SAF3、強磁性体(Ferromagnetic material:FM)であるPt/Co/AIOx、パーマロイ(permalloy)が材料として示されている。ここで、SAF1は、TaN/Pt/Co/Ni/Co/Ru/Co/Ni/Co/TaNであり、SAF2は、Ta/Pt/Co/Ni/Co/Ru/Co/Ni/Co/Taであり、SAF3は、TaN/Pt/Co/Ni/Co/Ru/Ru/Co/Ni/Co/TaNである。
Fig. 7 is a graph showing the domain wall velocity when various materials are used as the domain wall motion element in an experiment. The vertical axis of the graph in Fig. 7 shows the domain wall motion velocity V at the normalized current density. Fig. 7 shows the following materials: Mn 3 Ge, which is an antiferromagnetic material (AFM); Pt/BiYIG/GSGG, Mn 4-x Ni x N, and GdCo/Pt, which are ferrimagnetic materials (FI); SAF1, SAF2, and SAF3, which are synthetic antiferromagnetic materials (SAF); Pt/Co/AIO x , which are ferromagnetic materials (FM); and permalloy. Here, SAF1 is TaN/Pt/Co/Ni/Co/Ru/Co/Ni/Co/TaN, SAF2 is Ta/Pt/Co/Ni/Co/Ru/Co/Ni/Co/Ta, and SAF3 is TaN/Pt/Co/Ni/Co/Ru/Ru/Co/Ni/Co/TaN.
図7に示される通り、Mn3Geは、フェリ磁性体、合成反強磁性体や強磁性体といった他の材料と比較して、磁壁移動速度Vが圧倒的に大きいことが分かる。したがって、Mn3Geを磁壁移動素子に適用することにより、磁壁移動速度を向上させることが可能となる。
7, it is understood that Mn 3 Ge has an overwhelmingly high domain wall motion velocity V compared to other materials such as ferrimagnetic materials, synthetic antiferromagnetic materials, and ferromagnetic materials. Therefore, by applying Mn 3 Ge to a domain wall motion element, it is possible to improve the domain wall motion velocity.
以上の例では、非共線反強磁性体がMn3Geである例を示したが、本発明にかかる非共線反強磁性体はMn3Geに限られない。非共線性のスピン構造を有する反強磁性体からなり、電流が印加されることによって一方向に移動する磁壁を有する反強磁性層を備えるものであれば、本発明にかかる非共線反強磁性体は、他の種類の化合物であってもよい。他の種類の化合物としては、マンガン化合物が例として挙げられ、その例として、Mn3X(Xは、Ge、Sn、Ga、Rh、Pt、Ir等のいずれか)が想定される。
In the above example, the non-collinear antiferromagnetic material is Mn 3 Ge, but the non-collinear antiferromagnetic material according to the present invention is not limited to Mn 3 Ge. The non-collinear antiferromagnetic material according to the present invention may be another type of compound as long as it is made of an antiferromagnetic material having a non-collinear spin structure and has an antiferromagnetic layer having a domain wall that moves in one direction when a current is applied. An example of another type of compound is a manganese compound, and an example of this is Mn 3 X (X is any of Ge, Sn, Ga, Rh, Pt, Ir, etc.).
なお、反強磁性層の膜厚(すなわち、磁壁を移動させるシフト電流が流れる反強磁性層の平面に対して垂直な方向の、反強磁性層の厚み)は、例えば十nm-数百nmのオーダーであってもよい。また、膜厚の大きさは、これに限定されない。
The thickness of the antiferromagnetic layer (i.e., the thickness of the antiferromagnetic layer in the direction perpendicular to the plane of the antiferromagnetic layer through which the shift current that moves the domain wall flows) may be, for example, on the order of tens to hundreds of nm. Furthermore, the size of the film thickness is not limited to this.
また、磁壁移動素子に用いられる非共線反強磁性体は、多結晶よりも、単結晶のものとして生成されるのがより好ましい。ここで、単結晶は、理想的には、結晶のどの部分においても結晶軸の方向が同じとなる結晶であるが、格子欠陥又は結晶軸の向きの微小な変化の少なくともいずれかが部分的に含まれるような結晶も含まれる。単結晶は、多結晶と比較して結晶が規則的に積層されているため、ピニングサイトが生じにくく、磁壁がスムーズに移動しやすくなる。単結晶は、公知の任意の結晶育成法で生成することができる。
Furthermore, it is more preferable that the non-collinear antiferromagnetic material used in the domain wall motion element is produced as a single crystal rather than a polycrystal. Here, a single crystal is ideally a crystal in which the direction of the crystal axis is the same in every part of the crystal, but it also includes crystals that partially contain at least either lattice defects or minute changes in the direction of the crystal axis. Compared to polycrystals, single crystals are stacked in a regular pattern, so pinning sites are less likely to occur and domain walls are more likely to move smoothly. Single crystals can be produced by any known crystal growth method.
磁壁移動素子に組み込まれる非共線反強磁性体の加工は、集束イオンビーム(Focused Ion Beam:FIB)によって削り出されることによりなされてもよい。あるいは、成膜により、異なる物体の表面に非共線反強磁性体の層を形成させることで、磁壁移動素子が作成されてもよい。
The non-collinear antiferromagnetic material incorporated in the domain wall motion element may be processed by cutting it out with a focused ion beam (FIB). Alternatively, the domain wall motion element may be created by forming a layer of the non-collinear antiferromagnetic material on the surface of a different object by film deposition.
[効果の説明]
以上に示したように、本発明では、磁壁移動素子を、非共線反強磁性体からなり、電流が印加されることによって一方向に移動する磁壁を有する反強磁性層を備えるように構成することができる。この反強磁性体においては、電流が印加されることにより、スピン蓄積が磁壁周辺に形成されることで、磁壁が移動する。このようなメカニズムにより、このような反強磁性体は、フェリ磁性体、合成反強磁性体や強磁性体といった他の磁性体材料と比較して、磁壁移動速度を向上させることが可能となる。また、別の観点で言えば、このような反強磁性体は、他の磁性体材料と比較して、磁壁を同じ速度で移動させるのに必要な電流値を少なくすることができるため、省エネの効果を奏するともいえる。 [Effects]
As described above, in the present invention, the domain wall motion element can be configured to include an antiferromagnetic layer made of a non-collinear antiferromagnetic material and having a domain wall that moves in one direction when a current is applied. In this antiferromagnetic material, when a current is applied, spin accumulation is formed around the domain wall, causing the domain wall to move. Due to this mechanism, such an antiferromagnetic material can improve the domain wall motion speed compared to other magnetic materials such as ferrimagnetic materials, synthetic antiferromagnetic materials, and ferromagnetic materials. From another perspective, such an antiferromagnetic material can reduce the current value required to move the domain wall at the same speed compared to other magnetic materials, and therefore can be said to have an energy-saving effect.
以上に示したように、本発明では、磁壁移動素子を、非共線反強磁性体からなり、電流が印加されることによって一方向に移動する磁壁を有する反強磁性層を備えるように構成することができる。この反強磁性体においては、電流が印加されることにより、スピン蓄積が磁壁周辺に形成されることで、磁壁が移動する。このようなメカニズムにより、このような反強磁性体は、フェリ磁性体、合成反強磁性体や強磁性体といった他の磁性体材料と比較して、磁壁移動速度を向上させることが可能となる。また、別の観点で言えば、このような反強磁性体は、他の磁性体材料と比較して、磁壁を同じ速度で移動させるのに必要な電流値を少なくすることができるため、省エネの効果を奏するともいえる。 [Effects]
As described above, in the present invention, the domain wall motion element can be configured to include an antiferromagnetic layer made of a non-collinear antiferromagnetic material and having a domain wall that moves in one direction when a current is applied. In this antiferromagnetic material, when a current is applied, spin accumulation is formed around the domain wall, causing the domain wall to move. Due to this mechanism, such an antiferromagnetic material can improve the domain wall motion speed compared to other magnetic materials such as ferrimagnetic materials, synthetic antiferromagnetic materials, and ferromagnetic materials. From another perspective, such an antiferromagnetic material can reduce the current value required to move the domain wall at the same speed compared to other magnetic materials, and therefore can be said to have an energy-saving effect.
ここで、反強磁性体は、例えば、Mn3Ge、Mn3Sn、Mn3Ga、Mn3Rh、Mn3Pt、又はMn3Irのいずれかであってもよい。
Here, the antiferromagnetic material may be, for example, any one of Mn3Ge , Mn3Sn , Mn3Ga , Mn3Rh , Mn3Pt , and Mn3Ir .
また、反強磁性体は、結晶構造としてカゴメ格子を有し、磁壁が移動する方向(又は、シフト電流が印加される方向)は、カゴメ格子が形成する平面の法線ベクトルと略垂直な方向であってもよい。つまり、磁壁が移動する方向は、カゴメ面と略平行なベクトルを構成してもよい。ここで、略平行とは、磁壁が移動する方向がカゴメ面と平行であるか、又は平行に近い(例えば、磁壁が移動する方向とカゴメ面とのなす角が数度以下である)ことを意味する。これにより、磁壁移動速度をさらに高速にすることができる。
The antiferromagnetic material may have a kagome lattice as a crystal structure, and the direction in which the domain wall moves (or the direction in which the shift current is applied) may be approximately perpendicular to the normal vector of the plane formed by the kagome lattice. In other words, the direction in which the domain wall moves may form a vector that is approximately parallel to the kagome plane. Here, approximately parallel means that the direction in which the domain wall moves is parallel to the kagome plane or nearly parallel (for example, the angle between the direction in which the domain wall moves and the kagome plane is a few degrees or less). This can further increase the domain wall motion speed.
また、反強磁性層は単結晶で構成されてもよい。この構成により、ピニングサイトが生じにくく、磁壁がスムーズに移動しやすくなることで、磁壁移動速度をさらに高速にすることができる。
The antiferromagnetic layer may also be made of a single crystal. This configuration makes it difficult for pinning sites to occur and makes it easier for the domain walls to move smoothly, thereby making it possible to further increase the domain wall movement speed.
(1B)
次に、非共線反強磁性体の層と異なる層を積層させた磁壁移動素子の例を説明する。 (1B)
Next, an example of a domain wall motion element in which a non-collinear antiferromagnetic layer and a different layer are stacked will be described.
次に、非共線反強磁性体の層と異なる層を積層させた磁壁移動素子の例を説明する。 (1B)
Next, an example of a domain wall motion element in which a non-collinear antiferromagnetic layer and a different layer are stacked will be described.
図8は、磁壁移動素子のバリエーションを示す構成図である。図8において、磁壁移動素子Tは、Mn3Geによって構成された磁壁移動層11と、磁壁移動層11に対してz軸方向に積層されており、Pt(白金)によって構成されたスピンホール層12を備える。磁壁移動層11及びスピンホール層12は、xy平面上で延びており、z軸方向に所定の幅を有する。
Fig. 8 is a configuration diagram showing a variation of the domain wall motion element. In Fig. 8, the domain wall motion element T includes a domain wall motion layer 11 made of Mn 3 Ge, and a spin Hall layer 12 made of Pt (platinum) that is stacked in the z-axis direction on the domain wall motion layer 11. The domain wall motion layer 11 and the spin Hall layer 12 extend on the xy plane and have a predetermined width in the z-axis direction.
磁壁移動層11は、Mn3Geによって構成された層(反強磁性層)のことであり、その物性の詳細な説明は(1A)と同様であるため省略する。
The domain wall displacement layer 11 is a layer (antiferromagnetic layer) made of Mn 3 Ge, and detailed description of its physical properties is omitted since it is the same as that in (1A).
スピンホール層12では、電流jがx軸方向に流れたときに、x軸方向と垂直な方向であるz軸方向に、電子スピンの流れ(スピン流)が生じるスピンホール効果が生じる。図8では、異なるスピンを有する電子e1、e2が、z軸方向においてそれぞれ反対の方向に移動する状態が示されている。詳細には、y軸負方向にスピン偏極した電子e1がスピンホール層12のz軸負方向の側(すなわち、図8におけるスピンホール層12の下部側)に蓄積される一方、y軸正方向にスピン偏極した電子e2がスピンホール層12のz軸正方向の側(すなわち、図8におけるスピンホール層12の上部側)に蓄積される。このようにして、スピンホール層12にスピン流が生じる。
When a current j flows in the x-axis direction in the spin Hall layer 12, the spin Hall effect occurs, in which a flow of electron spins (spin current) occurs in the z-axis direction, which is perpendicular to the x-axis direction. Figure 8 shows a state in which electrons e1 and e2 with different spins move in opposite directions in the z-axis direction. In detail, electrons e1 spin-polarized in the negative y-axis direction are accumulated on the negative z-axis side of the spin Hall layer 12 (i.e., the lower side of the spin Hall layer 12 in Figure 8), while electrons e2 spin-polarized in the positive y-axis direction are accumulated on the positive z-axis side of the spin Hall layer 12 (i.e., the upper side of the spin Hall layer 12 in Figure 8). In this way, a spin current is generated in the spin Hall layer 12.
スピンホール層12の上部側、すなわち磁壁移動層11との境界面に蓄積された、スピン偏極した電子e2は、隣接する磁壁移動層11のMn3GeにおけるMnの磁気モーメントに対し、スピン軌道トルク(SOT:Spin Orbit Torque)を与える。このトルクにより、磁気八極子の極性反転を発生させることができる。つまり、磁気八極子に情報を書き込むことが可能となる。
The spin-polarized electrons e2 accumulated on the upper side of the spin Hall layer 12, i.e., on the interface with the domain wall displacement layer 11, exert a spin orbit torque (SOT) on the magnetic moment of Mn in the Mn 3 Ge of the adjacent domain wall displacement layer 11. This torque can cause the polarity of the magnetic octupole to be reversed. In other words, it becomes possible to write information to the magnetic octupole.
以上の例では、スピンホール層12がPtで構成される例を示したが、スピンホール層12はこれに限られず、スピン軌道相互作用の強い非磁性体の金属又は半導体といった材料で構成されていてもよい。このような非磁性体の金属の例としては、Pt(白金)のほか、W(タングステン)、Ta(タンタル)といったものが挙げられる。
In the above example, the spin Hall layer 12 is made of Pt, but the spin Hall layer 12 is not limited to this and may be made of a material such as a non-magnetic metal or semiconductor that has strong spin-orbit interaction. Examples of such non-magnetic metals include Pt (platinum), W (tungsten), and Ta (tantalum).
なお、磁壁移動層11の膜厚(すなわちz軸方向の幅)は、例えば(1A)に示した通り、十nm-数百nmのオーダーであってもよい。また、スピンホール層12の膜厚は、例えば十-数十nmのオーダーであってもよい。なお、スピンホール層12の膜厚を薄くするほど、スピンホール効果を生じさせるための電流を少なくすることができるため、省エネの効果を高くすることができる。ただし、スピンホール層12においてスピンホール効果を確実に発現させるためには、スピンホール層12は、上下の面にスピン偏極した電子が蓄積されるのに必要な膜厚(例えば10nm程度)を、少なくとも有することが好ましい。
The thickness of the domain wall displacement layer 11 (i.e., the width in the z-axis direction) may be on the order of tens to hundreds of nm, as shown in (1A). The thickness of the spin Hall layer 12 may be on the order of tens to tens of nm. The thinner the thickness of the spin Hall layer 12, the less current is required to generate the spin Hall effect, and the greater the energy saving effect. However, to ensure that the spin Hall effect is expressed in the spin Hall layer 12, it is preferable that the spin Hall layer 12 has at least the thickness (e.g., about 10 nm) required for spin-polarized electrons to accumulate on the top and bottom surfaces.
[効果の説明]
本発明では、磁壁移動素子を、磁壁移動層11と、その磁壁移動層11に積層された、Pt、Ta、Wの少なくともいずれかを有し、電流が印加されることによってスピンホール効果を発現するスピンホール層12をさらに備えるように構成することができる。このように、磁壁移動層11にスピンホール層12を積層させることにより、スピンホール層12に電流を流すことで、磁壁移動層11において高速に磁化反転を発生させることができる。そのため、磁気メモリデバイスとして磁壁移動素子Tを用いた場合に、磁壁移動層11へのデータの書込みが高速となる。また、データ書込み時において磁壁移動層11に直接電流を流す必要がないため、磁気メモリデバイスにおける書込みと読出しの動作において、磁壁移動層11に流す電流の経路を分けることができる。さらに、磁化反転に際して磁場を印加することが不要となる。 [Effects]
In the present invention, the domain wall motion element can be configured to further include a domainwall motion layer 11 and a spin Hall layer 12 having at least one of Pt, Ta, and W stacked on the domain wall motion layer 11, which exhibits the spin Hall effect when a current is applied. In this way, by stacking the spin Hall layer 12 on the domain wall motion layer 11, a magnetization reversal can be generated at high speed in the domain wall motion layer 11 by passing a current through the spin Hall layer 12. Therefore, when the domain wall motion element T is used as a magnetic memory device, data can be written at high speed to the domain wall motion layer 11. In addition, since there is no need to pass a current directly through the domain wall motion layer 11 when writing data, the path of the current flowing through the domain wall motion layer 11 can be separated in the write and read operations of the magnetic memory device. Furthermore, there is no need to apply a magnetic field when reversing magnetization.
本発明では、磁壁移動素子を、磁壁移動層11と、その磁壁移動層11に積層された、Pt、Ta、Wの少なくともいずれかを有し、電流が印加されることによってスピンホール効果を発現するスピンホール層12をさらに備えるように構成することができる。このように、磁壁移動層11にスピンホール層12を積層させることにより、スピンホール層12に電流を流すことで、磁壁移動層11において高速に磁化反転を発生させることができる。そのため、磁気メモリデバイスとして磁壁移動素子Tを用いた場合に、磁壁移動層11へのデータの書込みが高速となる。また、データ書込み時において磁壁移動層11に直接電流を流す必要がないため、磁気メモリデバイスにおける書込みと読出しの動作において、磁壁移動層11に流す電流の経路を分けることができる。さらに、磁化反転に際して磁場を印加することが不要となる。 [Effects]
In the present invention, the domain wall motion element can be configured to further include a domain
実施の形態2
次に、実施の形態1で説明した磁壁移動素子の適用例について説明する。Embodiment 2
Next, an application example of the domain wall motion element described in the first embodiment will be described.
次に、実施の形態1で説明した磁壁移動素子の適用例について説明する。
Next, an application example of the domain wall motion element described in the first embodiment will be described.
図9Aは、磁壁移動素子が適用されたメモリデバイスの概略的な構成図である。図9Aにおいて、メモリデバイスは、ASIC(Application Specific Integrated Circuit)100に搭載されており、レジスタ部101及びデータ読出線102を備える。
FIG. 9A is a schematic diagram of a memory device to which a domain wall motion element is applied. In FIG. 9A, the memory device is mounted on an ASIC (Application Specific Integrated Circuit) 100, and includes a register section 101 and a data read line 102.
レジスタ部101は、電流によって、内部のメモリにスピンの情報を書き込む。内部のメモリは、実施の形態1で示した、非共線反強磁性体であるMn3Geの層により構成された細線である。メモリの磁気八極子に対してレジスタ部101からスピン軌道トルクが与えられることで、磁化反転が発生し、データが書き込まれる。また、レジスタ部101は、シフト電流をメモリに対して流すことで、磁壁を移動させ、メモリの新たな領域に別の書込みをすることや、読み取り部に対してデータの読み取りをさせることを実現させる。このように、レジスタ部101は、データとして記録させた磁化の情報をシフトさせる機能を有するため、スピンシフトレジスタとも呼称される。磁化の情報は、レジスタ部101の読み取り部によって読み取られた後、電気信号としてデータ読出線102から出力される。
The register unit 101 writes spin information to the internal memory by a current. The internal memory is a thin wire composed of a layer of Mn 3 Ge, which is a non-collinear antiferromagnetic material, as shown in the first embodiment. A spin-orbit torque is applied from the register unit 101 to the magnetic octupole of the memory, causing magnetization reversal and writing data. The register unit 101 also moves a domain wall by passing a shift current through the memory, realizing another write in a new area of the memory and allowing the reading unit to read data. In this way, the register unit 101 has a function of shifting the magnetization information recorded as data, and is therefore also called a spin shift register. The magnetization information is read by the reading unit of the register unit 101 and then output from the data read line 102 as an electric signal.
図9Bは、レジスタ部101の詳細な構成図である。レジスタ部101は、導電体202を有する電流生成部201、スピンホール層203、磁気抵抗素子204及びメモリ線301を備える。
FIG. 9B is a detailed configuration diagram of the register unit 101. The register unit 101 includes a current generating unit 201 having a conductor 202, a spin Hall layer 203, a magnetoresistance element 204, and a memory line 301.
また、図9Cは、レジスタ部101の制御に関するユニットを示すブロック図である。ASIC100は、図9A、9Bに示した構成に加えて、制御部401、電流計測回路402及びデータ出力回路403といったハードウェア構成を備える。
FIG. 9C is a block diagram showing units related to the control of the register section 101. In addition to the configuration shown in FIGS. 9A and 9B, the ASIC 100 includes hardware configurations such as a control section 401, a current measurement circuit 402, and a data output circuit 403.
制御部401は、プロセッサ411及びメモリ412を有する。プロセッサ411は、CPU(Central Processing Unit)、MPU(Micro Processing Unit)、FPGA(Field-Programmable Gate Array)、DSP(Digital Signal Processor)等の任意のプロセッサを、1以上含むものである。
The control unit 401 has a processor 411 and a memory 412. The processor 411 includes one or more processors such as a CPU (Central Processing Unit), an MPU (Micro Processing Unit), an FPGA (Field-Programmable Gate Array), a DSP (Digital Signal Processor), etc.
メモリ412は、1以上の命令を格納するために使用される。ここで、1以上の命令は、ソフトウェアモジュール群(コンピュータプログラム)としてメモリ412に格納される。メモリ412は、揮発性メモリや不揮発性メモリ、又はそれらの組み合わせで構成される。メモリ412は、1個に限られず、複数設けられてもよい。なお、揮発性メモリは、例えば、DRAM (Dynamic Random Access Memory)、SRAM (Static Random Access Memory)等のRAM (Random Access Memory)であってもよい。不揮発性メモリは、例えば、PROM (Programmable ROM)、EPROM (Erasable Programmable Read Only Memory)、Flash Memoryであってもよい。
Memory 412 is used to store one or more instructions. Here, the one or more instructions are stored in memory 412 as a group of software modules (computer programs). Memory 412 is composed of volatile memory, non-volatile memory, or a combination of both. The number of memories 412 is not limited to one, and multiple memories 412 may be provided. The volatile memory may be, for example, RAM (Random Access Memory) such as DRAM (Dynamic Random Access Memory) or SRAM (Static Random Access Memory). The non-volatile memory may be, for example, PROM (Programmable ROM), EPROM (Erasable Programmable Read Only Memory), or Flash Memory.
プロセッサ411は、メモリ412と接続されており、1以上の命令をメモリ412から読み出して実行することで、制御部401が実行する以下の処理を行うことができる。なお、メモリ412は、プロセッサ411の外部に設けられていてもよいし、プロセッサ411に内蔵されていてもよい。
The processor 411 is connected to the memory 412, and can perform the following processing executed by the control unit 401 by reading and executing one or more instructions from the memory 412. Note that the memory 412 may be provided outside the processor 411, or may be built into the processor 411.
また、電流計測回路402及びデータ出力回路403は、下記に説明する機能を発揮することが可能な、任意の種類の電気回路である。
In addition, the current measurement circuit 402 and the data output circuit 403 are any type of electrical circuit capable of performing the functions described below.
以下、図9B及び図9Cを参照しながら、レジスタ部101の動作について説明する。図9Bにおいて、電流生成部201は、スピンホール層203を介してメモリ線301に情報を書き込むための電気信号を生成する。電流生成部201は、例えば、任意の光電変換素子を有してもよい。光電変換素子への入力光に応じて、この光電変換素子は、電気信号である電流を出力する。別の例として、電流生成部201は、制御部401によって制御されることで電気信号を生成する回路を有してもよい。
The operation of the register unit 101 will be described below with reference to Figures 9B and 9C. In Figure 9B, the current generating unit 201 generates an electrical signal for writing information to the memory line 301 via the spin hole layer 203. The current generating unit 201 may have, for example, any photoelectric conversion element. In response to light input to the photoelectric conversion element, this photoelectric conversion element outputs a current, which is an electrical signal. As another example, the current generating unit 201 may have a circuit that generates an electrical signal by being controlled by the control unit 401.
電流生成部201の導電体202は、スピンホール層203と接続されるほか、その両端が電源電圧及びグラウンドとそれぞれ接続されることによって、バイアス電圧Vが印加される。電流生成部201が電気信号を出力することで、導電体202は、電気信号に応じた書込み電流Iwをスピンホール層203に対して流す。
The conductor 202 of the current generating unit 201 is connected to the spin Hall layer 203, and both ends of the conductor 202 are connected to a power supply voltage and ground, respectively, so that a bias voltage V is applied. When the current generating unit 201 outputs an electrical signal, the conductor 202 passes a write current Iw corresponding to the electrical signal through the spin Hall layer 203.
スピンホール層203は、メモリ線301の一部と直交して重なっており(すなわち、積層されており)、(1B)で記載したスピンホール層12と同様の物性及び機能を有する。スピンホール層203に書込み電流Iwが流れると、(1B)に示したメカニズムにより、その内部にスピン流が生じる。
The spin Hall layer 203 overlaps (i.e., is stacked) with a portion of the memory line 301 perpendicularly, and has the same physical properties and functions as the spin Hall layer 12 described in (1B). When a write current Iw flows through the spin Hall layer 203, a spin current is generated therein by the mechanism shown in (1B).
メモリ線301は、非共線反強磁性体からなる磁壁移動層を有する磁壁移動素子であり、(1B)で示した磁壁移動層11と同様の物性及び機能を有する。そのため、メモリ線301の磁気八極子に対して、スピン流に起因したスピン軌道トルクが与えられることで、磁化反転が発生し、スピンホール層203と積層したメモリ線301の領域にデータが磁化の情報として書き込まれる。このようにして、電流生成部201及びスピンホール層203は、メモリ線301の磁区の磁化方向を定めることで、その磁区にデータを書き込む書込み部として機能する。
The memory line 301 is a domain wall motion element having a domain wall motion layer made of a non-collinear antiferromagnetic material, and has the same physical properties and functions as the domain wall motion layer 11 shown in (1B). Therefore, when a spin orbit torque caused by a spin current is applied to the magnetic octupole of the memory line 301, magnetization reversal occurs, and data is written as magnetization information in the region of the memory line 301 stacked with the spin Hall layer 203. In this way, the current generation unit 201 and the spin Hall layer 203 determine the magnetization direction of the magnetic domain of the memory line 301, and function as a write unit that writes data to that magnetic domain.
書き込まれる磁化の情報は、1ビットのデータ「0」又は「1」であり、図9Bでは、磁気八極子における磁化の情報が上向き(z軸正方向)であれば「0」、下向き(z軸負方向)であれば「1」と定義される。メモリ線301内では、この磁化の情報は磁壁によって、隣接した磁化の情報と区切られる。
The magnetization information written is one bit of data, "0" or "1." In FIG. 9B, if the magnetization information in the magnetic octupole is pointing upward (positive z-axis direction), it is defined as "0," and if it is pointing downward (negative z-axis direction), it is defined as "1." Within the memory line 301, this magnetization information is separated from adjacent magnetization information by a domain wall.
データが書き込まれた後、メモリ線301が延伸するx軸方向に対して、シフト電流Is(パルス電流)がメモリ線301に流される。なお、シフト電流Isを流すための回路がASIC100内又はASIC100外に設けられていてもよい。このシフト電流Isにより、磁化の情報は、(1A)に示したメカニズムの通り、メモリ線301内でx軸方向を移動して、スピンホール層203と離間した磁気抵抗素子204の位置まで移動する。
After the data is written, a shift current Is (pulse current) is passed through the memory line 301 in the x-axis direction along which the memory line 301 extends. A circuit for passing the shift current Is may be provided inside or outside the ASIC 100. This shift current Is causes the magnetization information to move in the x-axis direction within the memory line 301, as per the mechanism shown in (1A), to the position of the magnetoresistance element 204 separated from the spin Hall layer 203.
なお、シフト電流Isを流すタイミング及び流す時間については、任意に制御することが可能である。
The timing and duration of the shift current Is can be controlled as desired.
図9Dは、磁気抵抗素子204の詳細な構成図である。磁気抵抗素子204は、この例では磁気トンネル接合素子(MTJ素子)であり、メモリ線301の一部領域である記憶領域301Aと、非磁性層211と、磁化固定層212を有する。記憶領域301A、非磁性層211及び磁化固定層212は、この順に、図9Bのz軸方向に積層されている。
FIG. 9D is a detailed configuration diagram of the magnetoresistance element 204. In this example, the magnetoresistance element 204 is a magnetic tunnel junction element (MTJ element), and has a memory area 301A that is a partial area of the memory line 301, a nonmagnetic layer 211, and a magnetization fixed layer 212. The memory area 301A, nonmagnetic layer 211, and magnetization fixed layer 212 are stacked in this order in the z-axis direction of FIG. 9B.
記憶領域301Aには、上記の通り、1ビットのデータ「0」又は「1」が、磁化M11の情報として磁気八極子に書き込まれている。この磁化M11の情報は反転可能な情報であり、図9Dでは、上下両方向を向く矢印として示されている。また、シフト電流Isが流れることにより、メモリ線301の磁区が移動するため、記憶領域301Aに格納される磁化の情報は、シフト電流Isが流れることで変化する。
As described above, in memory area 301A, one bit of data "0" or "1" is written to the magnetic octupole as magnetization M11 information. This magnetization M11 information is reversible, and is shown in FIG. 9D as arrows pointing in both directions. In addition, because the magnetic domain of memory line 301 moves when shift current Is flows, the magnetization information stored in memory area 301A changes when shift current Is flows.
非磁性層211は、MgO等といった絶縁体で形成されており、記憶領域301Aと磁化固定層212とを分離する。
The non-magnetic layer 211 is made of an insulator such as MgO, and separates the memory area 301A from the magnetization fixed layer 212.
磁化固定層212は、磁化M12の方向が固定された層であり、例えば強磁性体又は反強磁性体で構成されている。磁化固定層212は、単結晶又は多結晶のいずれかで構成されている。なお、磁化M12は、図9Dにおいて上方向(z軸正方向)を向くとして説明を続けるが、磁化M12は下方向(z軸正方向)を向いていてもよい。
The magnetization fixed layer 212 is a layer in which the direction of magnetization M12 is fixed, and is made of, for example, a ferromagnetic material or an antiferromagnetic material. The magnetization fixed layer 212 is made of either a single crystal or a polycrystal. Note that, although the explanation will continue assuming that magnetization M12 faces upward (positive direction of the z-axis) in FIG. 9D, magnetization M12 may also face downward (positive direction of the z-axis).
記憶領域301Aの磁化M11と磁化固定層212の磁化M12が同じ向きである(平行状態である)とき、磁気抵抗素子204の抵抗は低い状態となる。しかしながら、磁化M11と磁化M12が反対の向きである(反平行状態である)とき、磁気抵抗素子204の抵抗は高い状態となる。
When the magnetization M11 of the memory area 301A and the magnetization M12 of the magnetization fixed layer 212 are in the same direction (parallel state), the resistance of the magnetoresistance element 204 is in a low state. However, when the magnetization M11 and the magnetization M12 are in opposite directions (anti-parallel state), the resistance of the magnetoresistance element 204 is in a high state.
また、記憶領域301Aにおいて非磁性層211が積層された面と反対側の面には、第1端子221が接続され、第1端子221には、トランジスタ222のドレインが接続されている。トランジスタ222は、例えばNMOS(N-channel metal oxide semiconductor)トランジスタであるが、他の種類のトランジスタであってもよい。トランジスタ222のゲートには、図9Cに示された制御部401が接続されており、制御部401は、トランジスタ222のオン及びオフを制御する。また、トランジスタ222のソースには、図示しない電源電圧が接続されている。
Furthermore, a first terminal 221 is connected to the surface of the memory area 301A opposite to the surface on which the nonmagnetic layer 211 is laminated, and the drain of a transistor 222 is connected to the first terminal 221. The transistor 222 is, for example, an NMOS (N-channel metal oxide semiconductor) transistor, but may be another type of transistor. The gate of the transistor 222 is connected to the control unit 401 shown in FIG. 9C, and the control unit 401 controls the on and off of the transistor 222. Furthermore, a power supply voltage (not shown) is connected to the source of the transistor 222.
さらに、磁化固定層212において非磁性層211が積層された面と反対側の面には、第2端子223が接続され、第2端子223には、読出し線224が接続されている。読出し線224は、電流計測回路402に接続されている。
Furthermore, a second terminal 223 is connected to the surface of the magnetization fixed layer 212 opposite to the surface on which the nonmagnetic layer 211 is laminated, and a read line 224 is connected to the second terminal 223. The read line 224 is connected to the current measurement circuit 402.
制御部401がトランジスタ222をオンにすることで、磁気抵抗素子204に所定の電圧が印加される。このようにして磁気抵抗素子204に電圧を加えることで、制御部401は、第1端子221から記憶領域301A、非磁性層211、磁化固定層212、第2端子223を経由して読出し線224に読出し電流を流す。このとき、磁気抵抗素子204に印可される電圧値が同じ場合であっても、磁気抵抗素子204の抵抗が高いか低いかに応じて(すなわち、磁気抵抗素子204が平行状態か反平行状態であるかに応じて)、読出し電流の電流値が変化する。
When the control unit 401 turns on the transistor 222, a predetermined voltage is applied to the magnetoresistance element 204. By applying a voltage to the magnetoresistance element 204 in this manner, the control unit 401 passes a read current from the first terminal 221 through the memory area 301A, the nonmagnetic layer 211, the magnetization fixed layer 212, and the second terminal 223 to the read line 224. At this time, even if the voltage value applied to the magnetoresistance element 204 is the same, the current value of the read current changes depending on whether the resistance of the magnetoresistance element 204 is high or low (i.e., depending on whether the magnetoresistance element 204 is in a parallel or anti-parallel state).
図9Cに示された電流計測回路402は、読出し電流の電流値を計測し、計測値を制御部401に出力する。制御部401は、その計測値を用いて、磁気抵抗素子204が平行状態か反平行状態であるかを判定する。制御部401は、例えば電流の所定の閾値と、計測値との大小を比較することにより、磁気抵抗素子204が平行状態か反平行状態であるかを判定する。また、制御部401は、磁化固定層212の磁化M12の向きの情報を取得する。この情報は、例えばメモリ412に格納されている。
The current measurement circuit 402 shown in FIG. 9C measures the current value of the read current and outputs the measurement value to the control unit 401. The control unit 401 uses the measurement value to determine whether the magnetoresistance element 204 is in a parallel or anti-parallel state. The control unit 401 determines whether the magnetoresistance element 204 is in a parallel or anti-parallel state, for example, by comparing the magnitude of a predetermined current threshold with the measurement value. The control unit 401 also obtains information on the direction of magnetization M12 of the magnetization fixed layer 212. This information is stored in, for example, the memory 412.
制御部401は、磁気抵抗素子204が平行状態か反平行状態を示す判定結果と、磁化M12の向きの情報に基づいて、記憶領域301Aの磁化M11の情報が、「0」又は「1」のいずれを示すかを判定する。制御部401は、データ出力回路403を制御して、判定した「0」又は「1」の結果を、電気信号としてデータ読出線102から出力させる。以上に示した通り、磁気抵抗素子204、電流計測回路402及び制御部401は、記憶領域301Aの磁化情報を読み取る読み取り部として機能する。
The control unit 401 determines whether the information of the magnetization M11 of the memory area 301A indicates "0" or "1" based on the determination result indicating whether the magnetoresistance element 204 is in a parallel or anti-parallel state and the information on the direction of the magnetization M12. The control unit 401 controls the data output circuit 403 to output the determined result of "0" or "1" as an electrical signal from the data read line 102. As described above, the magnetoresistance element 204, the current measurement circuit 402, and the control unit 401 function as a reading unit that reads the magnetization information of the memory area 301A.
[効果の説明]
本発明では、ASIC100としてのメモリデバイスを、非共線反強磁性体からなる磁壁移動層を有するメモリ線301と、メモリ線301の磁区の磁化方向を制御することで、磁区にデータを書き込む書込み部と、電流が印加されることでメモリ線301内で移動した磁区の磁化方向を読み取る読み取り部を備えるように構成することができる。このように、実施の形態1で示した磁性体をメモリデバイス内に組み込むことにより、メモリデバイスは、実施の形態1で記載した効果を奏する。 [Effects]
In the present invention, a memory device serving as anASIC 100 can be configured to include a memory line 301 having a domain wall motion layer made of a non-collinear antiferromagnetic material, a write unit that writes data into the magnetic domain by controlling the magnetization direction of the magnetic domain of the memory line 301, and a read unit that reads the magnetization direction of the magnetic domain that has moved in the memory line 301 by applying a current. In this way, by incorporating the magnetic material shown in the first embodiment into the memory device, the memory device exhibits the effects described in the first embodiment.
本発明では、ASIC100としてのメモリデバイスを、非共線反強磁性体からなる磁壁移動層を有するメモリ線301と、メモリ線301の磁区の磁化方向を制御することで、磁区にデータを書き込む書込み部と、電流が印加されることでメモリ線301内で移動した磁区の磁化方向を読み取る読み取り部を備えるように構成することができる。このように、実施の形態1で示した磁性体をメモリデバイス内に組み込むことにより、メモリデバイスは、実施の形態1で記載した効果を奏する。 [Effects]
In the present invention, a memory device serving as an
また、メモリデバイスは、光電変換素子をさらに備えていてもよい。メモリデバイスの書込み部は、入力光に応じて光電変換素子が出力した電気信号を用いて磁区の磁化方向を制御し、磁区にデータを書き込む。このようにして、メモリデバイスは、入力光に応じたデータ書込みが可能となる。
The memory device may further include a photoelectric conversion element. The writing section of the memory device controls the magnetization direction of the magnetic domains using the electrical signal output by the photoelectric conversion element in response to the input light, and writes data to the magnetic domains. In this way, the memory device is capable of writing data in response to the input light.
また、本発明は、非共線反強磁性体からなる磁壁移動層の磁区の磁化方向を制御することで、その磁区にデータを書き込む第1のステップと、磁壁移動層に電流を印加することで、磁壁移動層の一方向に磁区を移動させる第2のステップとを有するデータ書込み方法としてもとらえることができる。このようなデータ書込みの方法を採用することにより、実施の形態1で記載した効果を奏する。
The present invention can also be considered as a data writing method having a first step of writing data to a magnetic domain in a magnetic domain wall displacement layer made of a non-collinear antiferromagnetic material by controlling the magnetization direction of the magnetic domain, and a second step of moving the magnetic domain in one direction in the magnetic domain wall displacement layer by applying a current to the magnetic domain wall displacement layer. By employing such a data writing method, the effects described in the first embodiment can be achieved.
また、第1及び第2のステップを複数回繰り返し実行することにより、多くのデータを、メモリデバイスの磁壁移動層の異なる領域に連続して格納させることができる。
In addition, by repeatedly performing the first and second steps multiple times, a large amount of data can be stored continuously in different regions of the domain wall displacement layer of the memory device.
なお、シフト電流Isのベクトルが、メモリ線301におけるMn3Geのカゴメ面の平面と略平行となる場合に、実施の形態1に示した通り、磁壁の移動速度は最大となり、高速でデータ書込みをできるという効果を向上させることができる。しかしながら、シフト電流Isのベクトルが、メモリ線301におけるMn3Geのカゴメ面の平面と略垂直である場合でも、磁壁の移動速度は、公知の材料における磁壁の移動速度と比較すると、非常に速いものとなる。
When the vector of the shift current Is is approximately parallel to the plane of the kagome surface of Mn 3 Ge in the memory line 301, the domain wall motion speed is maximized, and the effect of high-speed data writing can be improved as shown in the first embodiment. However, even when the vector of the shift current Is is approximately perpendicular to the plane of the kagome surface of Mn 3 Ge in the memory line 301, the domain wall motion speed is very fast compared to the domain wall motion speed in known materials.
メモリ線301を構成する非共線反強磁性体の材料は、Mn3Geに限らず、実施の形態1で示した各種材料であってもよい。
The material of the non-collinear antiferromagnetic material constituting the memory line 301 is not limited to Mn 3 Ge, and may be any of the various materials shown in the first embodiment.
ASIC100は、任意の機器に適用することが可能である。例えば、ASIC100は、光通信の機器に適用することが可能である。その場合、電流生成部201が有する光電変換素子への入力光は、例えばASIC100以外の機器から出力された任意の信号光である。ただし、ASIC100は、それ以外の用途に適用することも可能であり、その場合、入力光は、自然光など、機器から出力されていない光であってもよい。
The ASIC 100 can be applied to any device. For example, the ASIC 100 can be applied to optical communication devices. In that case, the input light to the photoelectric conversion element of the current generating unit 201 is, for example, any signal light output from a device other than the ASIC 100. However, the ASIC 100 can also be applied to other uses, in which case the input light may be light that is not output from the device, such as natural light.
また、ASIC100において、電流生成部201は必須ではない。例えば、ASIC100は、ASIC100以外の機器から出力された書込み電流を取得し、その書込み電流をそのまま、又は任意の前処理を施した上でスピンホール層203に流すことにより、書込み電流に応じたデータをメモリ線301に書き込んでも良い。
Furthermore, the current generating unit 201 is not essential to the ASIC 100. For example, the ASIC 100 may obtain a write current output from a device other than the ASIC 100, and pass the write current directly or after performing any pre-processing to the spin hole layer 203, thereby writing data corresponding to the write current to the memory line 301.
また、図9Cに示すハードウェア構成は、ASIC100の内部に限らず、外部に設けられていても良い。
In addition, the hardware configuration shown in FIG. 9C is not limited to being inside the ASIC 100, but may be provided externally.
以上、実施の形態を参照して本発明を説明したが、本発明は上記実施の形態によって記載された内容に限定されるものではなく、趣旨を逸脱しない範囲で適宜変更することが可能である。
The present invention has been described above with reference to the embodiments, but the present invention is not limited to the contents described in the above embodiments, and can be modified as appropriate without departing from the spirit of the invention.
例えば、本発明における非共線反強磁性体を、その反強磁性層に歪みが導入されるように生成することで、磁気八極子の偏極の自由度を、確実に膜面垂直方向の2値にするように構成してもよい。これにより、磁気メモリデバイスにおけるデジタルデータの書込み及び読み取りをより容易にすることができる。
For example, the non-collinear antiferromagnetic material of the present invention may be configured so that distortion is introduced into the antiferromagnetic layer, ensuring that the degree of freedom of the polarization of the magnetic octupole is two-valued in the direction perpendicular to the film surface. This makes it easier to write and read digital data in a magnetic memory device.
また、実施の形態2に示したメモリデバイスはあくまで一例であり、非共線反強磁性体を用いた磁壁移動素子は、他の種類のメモリデバイスに適用することが可能である。例えば、磁壁移動素子は、SOT-MRAM(Magnetoresistive Random Access Memory)に適用されてもよい。
Furthermore, the memory device shown in the second embodiment is merely one example, and the domain wall motion element using a non-collinear antiferromagnetic material can be applied to other types of memory devices. For example, the domain wall motion element may be applied to SOT-MRAM (Magnetoresistive Random Access Memory).
SOT-MRAMでは、複数のメモリセルがマトリクス状に配置され、複数のメモリセルの各々が、データの書込み及び読出しのためのビット線及びワード線に接続されている。また、各メモリセルは、MTJ素子を有する。このMTJ素子は、実施の形態2に記載の通り、非共線反強磁性体を用いた記憶領域301A、非磁性層211及び磁化固定層212が順に積層されたものである。ただし、記憶領域301Aは細線として構成されず、各MTJ素子に個別に(すなわち、MTJ素子毎に分離して)設けられている。また、記憶領域301Aにおいて非磁性層211と反対側に形成された面には、ビット線及びワード線と接続されたスピンホール層が積層されている。詳細には、ドレインでそのスピンホール層と接続された第1のトランジスタが、そのソースで第1のビット線に、そのゲートでワード線に接続される。また、ドレインでそのスピンホール層と接続された第2のトランジスタは、そのソースで第2のビット線に、そのゲートで、第1のトランジスタと共通のワード線に接続される。MTJ素子の構成におけるその他の点については、実施の形態2における磁気抵抗素子204と同様であるため、説明を省略する。
In the SOT-MRAM, a plurality of memory cells are arranged in a matrix, and each of the plurality of memory cells is connected to a bit line and a word line for writing and reading data. Each memory cell has an MTJ element. As described in the second embodiment, this MTJ element is formed by sequentially stacking a memory area 301A using a non-collinear antiferromagnetic material, a non-magnetic layer 211, and a magnetization fixed layer 212. However, the memory area 301A is not configured as a fine line, but is provided individually for each MTJ element (i.e., separated for each MTJ element). In addition, a spin-hole layer connected to a bit line and a word line is stacked on the surface formed on the opposite side of the non-magnetic layer 211 in the memory area 301A. In detail, a first transistor connected to the spin-hole layer at the drain is connected to the first bit line at its source and to the word line at its gate. In addition, a second transistor connected to the spin-hole layer at the drain is connected to the second bit line at its source and to the word line common to the first transistor at its gate. Other aspects of the MTJ element configuration are similar to the magnetoresistance element 204 in embodiment 2, so the description will be omitted.
制御部401は、書込みを実行するために、ビット線及びワード線における電圧レベルを制御する。詳細には、制御部401は、ワード線における電圧レベルをHレベルに設定し、第1のビット線及び第2のビット線の一方における電圧レベルをHレベルに、他方における電圧レベルをLレベルに設定する。第1のビット線及び第2のビット線のいずれをHレベルにするかを変更することで、スピンホール層に流れる電流の向きを変更することが可能となる。スピンホール層に流れる電流の向きに応じて、実施の形態1及び2で説明したメカニズムにより、記憶領域301Aにおいて磁化情報を記憶させることができる。ここで、制御部401は、各ビット線及びワード線の電圧レベルを制御することで、マトリクス状に配置された複数のメモリセルの各々において、異なるデジタル情報を格納させることができる。
The control unit 401 controls the voltage levels on the bit lines and word lines to perform writing. In detail, the control unit 401 sets the voltage level on the word lines to the H level, and sets the voltage level on one of the first bit line and the second bit line to the H level and the voltage level on the other to the L level. By changing which of the first bit line and the second bit line is set to the H level, it is possible to change the direction of the current flowing through the spin hole layer. Depending on the direction of the current flowing through the spin hole layer, magnetization information can be stored in the memory area 301A by the mechanism described in the first and second embodiments. Here, the control unit 401 controls the voltage levels of each bit line and word line, thereby storing different digital information in each of the multiple memory cells arranged in a matrix.
また、制御部401は、ワード線における電圧レベルをHレベルに設定し、第1のビット線及び第2のビット線の一方における電圧レベルをHレベルに、他方を開放状態とすることで、メモリセルに読出し電流を流すことで、データの読出しを実行することができる。このデータの読出しの詳細については、実施の形態2に記載した通りであるため、説明を省略する。
The control unit 401 also sets the voltage level of the word line to the H level, and sets the voltage level of one of the first bit line and the second bit line to the H level and leaves the other in an open state, thereby passing a read current through the memory cell and reading data. Details of this data reading are as described in the second embodiment, and therefore will not be described here.
さらに、上記の実施形態の一部又は全部は、以下の付記のようにも記載されうるが、以下には限られない。
(付記1)
非共線性のスピン構造を有する反強磁性体からなり、電流が印加されることによって一方向に移動する磁壁を有する反強磁性層を備える磁壁移動素子。
(付記2)
前記反強磁性体は、Mn3Ge、Mn3Sn、Mn3Ga、Mn3Rh、Mn3Pt、又はMn3Irのいずれかである、
付記1に記載の磁壁移動素子。
(付記3)
前記反強磁性体は、結晶構造としてカゴメ格子を有し、
前記磁壁が移動する前記一方向は、前記カゴメ格子が形成する平面の法線ベクトルと略垂直な方向である、
付記1又は2に記載の磁壁移動素子。
(付記4)
前記反強磁性層は単結晶で構成される、
付記1乃至3のいずれか1項に記載の磁壁移動素子。
(付記5)
前記反強磁性層に積層された、Pt、Ta、Wの少なくともいずれかを有し、電流が印加されることによってスピンホール効果を発現するスピンホール層をさらに備える、
付記1乃至4のいずれか1項に記載の磁壁移動素子。
(付記6)
非共線性のスピン構造を有する反強磁性体からなる反強磁性層を有する磁壁移動素子と、
前記反強磁性層の磁区の磁化方向を定めることで、前記磁区にデータを書き込む書込み部と、
電流が前記反強磁性層に印加されることによって前記磁壁移動素子内で移動した前記磁区の磁化方向を読み取る読み取り部と、
を備えるメモリデバイス。
(付記7)
前記書込み部は、入力光に応じた電気信号を出力する光電変換素子を有し、前記光電変換素子が出力した電気信号を用いて前記磁区の磁化方向を制御し、前記磁区にデータを書き込む、
付記6に記載のメモリデバイス。
(付記8)
非共線性のスピン構造を有する反強磁性体からなる反強磁性層の磁区の磁化方向を制御することで、前記磁区にデータを書き込む第1のステップと、
前記反強磁性層に電流を印加することで、前記反強磁性層の一方向に前記磁区を移動させる第2のステップと、
を有するデータ書込み方法。
(付記9)
前記第1及び第2のステップを複数回繰り返し実行する、
付記8に記載のデータ書込み方法。 Furthermore, some or all of the above-described embodiments can be described as, but are not limited to, the following supplementary notes.
(Appendix 1)
A domain wall motion element is provided with an antiferromagnetic layer made of an antiferromagnetic material having a non-collinear spin structure, the antiferromagnetic layer having a domain wall that moves in one direction when a current is applied thereto.
(Appendix 2)
The antiferromagnetic material is any one of Mn 3 Ge, Mn 3 Sn, Mn 3 Ga, Mn 3 Rh, Mn 3 Pt, and Mn 3 Ir.
2. The domain wall motion element according toclaim 1.
(Appendix 3)
the antiferromagnetic material has a kagome lattice as a crystal structure,
The one direction in which the domain wall moves is a direction substantially perpendicular to a normal vector of a plane formed by the Kagome lattice.
3. The domain wall motion element according to claim 1 or 2.
(Appendix 4)
The antiferromagnetic layer is made of a single crystal.
4. The domain wall motion element according toclaim 1 .
(Appendix 5)
A spin Hall layer is further provided on the antiferromagnetic layer, the spin Hall layer having at least one of Pt, Ta, and W, and exhibiting a spin Hall effect when a current is applied thereto.
5. The domain wall motion element according toclaim 1 .
(Appendix 6)
a domain wall motion element having an antiferromagnetic layer made of an antiferromagnetic material having a non-collinear spin structure;
a writing unit that writes data into the magnetic domains by determining the magnetization direction of the magnetic domains of the antiferromagnetic layer;
a reading unit that reads the magnetization direction of the magnetic domain that has moved in the domain wall motion element by applying a current to the antiferromagnetic layer;
A memory device comprising:
(Appendix 7)
the writing unit has a photoelectric conversion element that outputs an electrical signal according to input light, and controls the magnetization direction of the magnetic domain using the electrical signal output by the photoelectric conversion element to write data in the magnetic domain.
7. The memory device ofclaim 6.
(Appendix 8)
a first step of writing data to a magnetic domain by controlling the magnetization direction of the magnetic domain of an antiferromagnetic layer made of an antiferromagnetic material having a non-collinear spin structure;
a second step of applying a current to the antiferromagnetic layer to move the magnetic domain in one direction across the antiferromagnetic layer;
The data writing method includes the steps of:
(Appendix 9)
Repeating the first and second steps a number of times;
9. The data writing method according toclaim 8.
(付記1)
非共線性のスピン構造を有する反強磁性体からなり、電流が印加されることによって一方向に移動する磁壁を有する反強磁性層を備える磁壁移動素子。
(付記2)
前記反強磁性体は、Mn3Ge、Mn3Sn、Mn3Ga、Mn3Rh、Mn3Pt、又はMn3Irのいずれかである、
付記1に記載の磁壁移動素子。
(付記3)
前記反強磁性体は、結晶構造としてカゴメ格子を有し、
前記磁壁が移動する前記一方向は、前記カゴメ格子が形成する平面の法線ベクトルと略垂直な方向である、
付記1又は2に記載の磁壁移動素子。
(付記4)
前記反強磁性層は単結晶で構成される、
付記1乃至3のいずれか1項に記載の磁壁移動素子。
(付記5)
前記反強磁性層に積層された、Pt、Ta、Wの少なくともいずれかを有し、電流が印加されることによってスピンホール効果を発現するスピンホール層をさらに備える、
付記1乃至4のいずれか1項に記載の磁壁移動素子。
(付記6)
非共線性のスピン構造を有する反強磁性体からなる反強磁性層を有する磁壁移動素子と、
前記反強磁性層の磁区の磁化方向を定めることで、前記磁区にデータを書き込む書込み部と、
電流が前記反強磁性層に印加されることによって前記磁壁移動素子内で移動した前記磁区の磁化方向を読み取る読み取り部と、
を備えるメモリデバイス。
(付記7)
前記書込み部は、入力光に応じた電気信号を出力する光電変換素子を有し、前記光電変換素子が出力した電気信号を用いて前記磁区の磁化方向を制御し、前記磁区にデータを書き込む、
付記6に記載のメモリデバイス。
(付記8)
非共線性のスピン構造を有する反強磁性体からなる反強磁性層の磁区の磁化方向を制御することで、前記磁区にデータを書き込む第1のステップと、
前記反強磁性層に電流を印加することで、前記反強磁性層の一方向に前記磁区を移動させる第2のステップと、
を有するデータ書込み方法。
(付記9)
前記第1及び第2のステップを複数回繰り返し実行する、
付記8に記載のデータ書込み方法。 Furthermore, some or all of the above-described embodiments can be described as, but are not limited to, the following supplementary notes.
(Appendix 1)
A domain wall motion element is provided with an antiferromagnetic layer made of an antiferromagnetic material having a non-collinear spin structure, the antiferromagnetic layer having a domain wall that moves in one direction when a current is applied thereto.
(Appendix 2)
The antiferromagnetic material is any one of Mn 3 Ge, Mn 3 Sn, Mn 3 Ga, Mn 3 Rh, Mn 3 Pt, and Mn 3 Ir.
2. The domain wall motion element according to
(Appendix 3)
the antiferromagnetic material has a kagome lattice as a crystal structure,
The one direction in which the domain wall moves is a direction substantially perpendicular to a normal vector of a plane formed by the Kagome lattice.
3. The domain wall motion element according to
(Appendix 4)
The antiferromagnetic layer is made of a single crystal.
4. The domain wall motion element according to
(Appendix 5)
A spin Hall layer is further provided on the antiferromagnetic layer, the spin Hall layer having at least one of Pt, Ta, and W, and exhibiting a spin Hall effect when a current is applied thereto.
5. The domain wall motion element according to
(Appendix 6)
a domain wall motion element having an antiferromagnetic layer made of an antiferromagnetic material having a non-collinear spin structure;
a writing unit that writes data into the magnetic domains by determining the magnetization direction of the magnetic domains of the antiferromagnetic layer;
a reading unit that reads the magnetization direction of the magnetic domain that has moved in the domain wall motion element by applying a current to the antiferromagnetic layer;
A memory device comprising:
(Appendix 7)
the writing unit has a photoelectric conversion element that outputs an electrical signal according to input light, and controls the magnetization direction of the magnetic domain using the electrical signal output by the photoelectric conversion element to write data in the magnetic domain.
7. The memory device of
(Appendix 8)
a first step of writing data to a magnetic domain by controlling the magnetization direction of the magnetic domain of an antiferromagnetic layer made of an antiferromagnetic material having a non-collinear spin structure;
a second step of applying a current to the antiferromagnetic layer to move the magnetic domain in one direction across the antiferromagnetic layer;
The data writing method includes the steps of:
(Appendix 9)
Repeating the first and second steps a number of times;
9. The data writing method according to
これらの例に示したように、本発明の構成や詳細には、その技術的思想の範囲内で当業者が理解し得る様々な変更をすることができる。
As shown in these examples, the configuration and details of the present invention can be modified in various ways that are understandable to those skilled in the art and fall within the scope of the technical concept.
この出願は、2022年10月28日に出願された日本出願特願2022-173144を基礎とする優先権を主張し、その開示の全てをここに取り込む。
This application claims priority based on Japanese Patent Application No. 2022-173144, filed on October 28, 2022, the entire disclosure of which is incorporated herein by reference.
M 反強磁性層
F 強磁性層
T 磁壁移動素子
11 磁壁移動層
12 スピンホール層
100 ASIC
101 レジスタ部
102 データ読出線
201 電流生成部
202 導電体
203 スピンホール層
204 磁気抵抗素子
211 非磁性層
212 磁化固定層
221 第1端子
222 トランジスタ
223 第2端子
224 読出し線
301 メモリ線
301A 記憶領域
401 制御部
402 電流計測回路
403 データ出力回路
411 プロセッサ
412 メモリ M: antiferromagnetic layer F: ferromagnetic layer T: domain wall motion element 11: domain wall motion layer 12: spin Hall layer 100: ASIC
101Register section 102 Data read line 201 Current generating section 202 Conductor 203 Spin Hall layer 204 Magnetoresistance element 211 Nonmagnetic layer 212 Magnetization fixed layer 221 First terminal 222 Transistor 223 Second terminal 224 Read line 301 Memory line 301A Storage area 401 Control section 402 Current measuring circuit 403 Data output circuit 411 Processor 412 Memory
F 強磁性層
T 磁壁移動素子
11 磁壁移動層
12 スピンホール層
100 ASIC
101 レジスタ部
102 データ読出線
201 電流生成部
202 導電体
203 スピンホール層
204 磁気抵抗素子
211 非磁性層
212 磁化固定層
221 第1端子
222 トランジスタ
223 第2端子
224 読出し線
301 メモリ線
301A 記憶領域
401 制御部
402 電流計測回路
403 データ出力回路
411 プロセッサ
412 メモリ M: antiferromagnetic layer F: ferromagnetic layer T: domain wall motion element 11: domain wall motion layer 12: spin Hall layer 100: ASIC
101
Claims (9)
- 非共線性のスピン構造を有する反強磁性体からなり、電流が印加されることによって一方向に移動する磁壁を有する反強磁性層を備える磁壁移動素子。 A domain wall motion element made of an antiferromagnetic material with a non-collinear spin structure, equipped with an antiferromagnetic layer having a domain wall that moves in one direction when a current is applied.
- 前記反強磁性体は、Mn3Ge、Mn3Sn、Mn3Ga、Mn3Rh、Mn3Pt、又はMn3Irのいずれかである、
請求項1に記載の磁壁移動素子。 The antiferromagnetic material is any one of Mn 3 Ge, Mn 3 Sn, Mn 3 Ga, Mn 3 Rh, Mn 3 Pt, and Mn 3 Ir.
The domain wall motion element according to claim 1 . - 前記反強磁性体は、結晶構造としてカゴメ格子を有し、
前記磁壁が移動する前記一方向は、前記カゴメ格子が形成する平面の法線ベクトルと略垂直な方向である、
請求項1又は2に記載の磁壁移動素子。 the antiferromagnetic material has a kagome lattice as a crystal structure,
The one direction in which the domain wall moves is a direction substantially perpendicular to a normal vector of a plane formed by the Kagome lattice.
The domain wall motion element according to claim 1 or 2. - 前記反強磁性層は単結晶で構成される、
請求項1乃至3のいずれか1項に記載の磁壁移動素子。 The antiferromagnetic layer is made of a single crystal.
The domain wall motion element according to claim 1 . - 前記反強磁性層に積層された、Pt、Ta、Wの少なくともいずれかを有し、電流が印加されることによってスピンホール効果を発現するスピンホール層をさらに備える、
請求項1乃至4のいずれか1項に記載の磁壁移動素子。 A spin Hall layer is laminated on the antiferromagnetic layer and contains at least one of Pt, Ta, and W, and exhibits a spin Hall effect when a current is applied thereto.
The domain wall motion element according to claim 1 . - 非共線性のスピン構造を有する反強磁性体からなる反強磁性層を有する磁壁移動素子と、
前記反強磁性層の磁区の磁化方向を定めることで、前記磁区にデータを書き込む書込み部と、
電流が前記反強磁性層に印加されることによって前記磁壁移動素子内で移動した前記磁区の磁化方向を読み取る読み取り部と、
を備えるメモリデバイス。 a domain wall motion element having an antiferromagnetic layer made of an antiferromagnetic material having a non-collinear spin structure;
a writing unit that writes data into the magnetic domains by determining the magnetization direction of the magnetic domains of the antiferromagnetic layer;
a reading unit that reads the magnetization direction of the magnetic domain that has moved in the domain wall motion element by applying a current to the antiferromagnetic layer;
A memory device comprising: - 前記書込み部は、入力光に応じた電気信号を出力する光電変換素子を有し、前記光電変換素子が出力した電気信号を用いて前記磁区の磁化方向を制御し、前記磁区にデータを書き込む、
請求項6に記載のメモリデバイス。 the writing unit has a photoelectric conversion element that outputs an electrical signal according to input light, and controls the magnetization direction of the magnetic domain using the electrical signal output by the photoelectric conversion element to write data in the magnetic domain.
The memory device of claim 6. - 非共線性のスピン構造を有する反強磁性体からなる反強磁性層の磁区の磁化方向を制御することで、前記磁区にデータを書き込む第1のステップと、
前記反強磁性層に電流を印加することで、前記反強磁性層の一方向に前記磁区を移動させる第2のステップと、
を有するデータ書込み方法。 a first step of writing data to a magnetic domain by controlling the magnetization direction of the magnetic domain of an antiferromagnetic layer made of an antiferromagnetic material having a non-collinear spin structure;
a second step of applying a current to the antiferromagnetic layer to move the magnetic domain in one direction across the antiferromagnetic layer;
The data writing method includes the steps of: - 前記第1及び第2のステップを複数回繰り返し実行する、
請求項8に記載のデータ書込み方法。 Repeating the first and second steps a number of times;
The data writing method according to claim 8.
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WO2022158545A1 (en) * | 2021-01-20 | 2022-07-28 | 国立大学法人東京大学 | Photonic spin register, information writing method, and information read-out method |
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