WO2016186178A1 - ノンコリニア磁気抵抗素子 - Google Patents
ノンコリニア磁気抵抗素子 Download PDFInfo
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- WO2016186178A1 WO2016186178A1 PCT/JP2016/064924 JP2016064924W WO2016186178A1 WO 2016186178 A1 WO2016186178 A1 WO 2016186178A1 JP 2016064924 W JP2016064924 W JP 2016064924W WO 2016186178 A1 WO2016186178 A1 WO 2016186178A1
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- 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
- G11C11/165—Auxiliary circuits
- G11C11/1675—Writing or programming circuits or methods
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- 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
- G11C11/161—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 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F10/00—Thin magnetic films, e.g. of one-domain structure
- H01F10/32—Spin-exchange-coupled multilayers, e.g. nanostructured superlattices
- H01F10/3227—Exchange coupling via one or more magnetisable ultrathin or granular films
- H01F10/3231—Exchange coupling via one or more magnetisable ultrathin or granular films via a non-magnetic spacer
- H01F10/3236—Exchange coupling via one or more magnetisable ultrathin or granular films via a non-magnetic spacer made of a noble metal, e.g.(Co/Pt) n multilayers having perpendicular anisotropy
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F10/00—Thin magnetic films, e.g. of one-domain structure
- H01F10/32—Spin-exchange-coupled multilayers, e.g. nanostructured superlattices
- H01F10/324—Exchange coupling of magnetic film pairs via a very thin non-magnetic spacer, e.g. by exchange with conduction electrons of the spacer
- H01F10/3286—Spin-exchange coupled multilayers having at least one layer with perpendicular magnetic anisotropy
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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
- H10N50/00—Galvanomagnetic devices
- H10N50/10—Magnetoresistive 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
- H10N50/00—Galvanomagnetic devices
- H10N50/80—Constructional details
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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
- H10N50/00—Galvanomagnetic devices
- H10N50/80—Constructional details
- H10N50/85—Magnetic active materials
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F10/00—Thin magnetic films, e.g. of one-domain structure
- H01F10/32—Spin-exchange-coupled multilayers, e.g. nanostructured superlattices
- H01F10/324—Exchange coupling of magnetic film pairs via a very thin non-magnetic spacer, e.g. by exchange with conduction electrons of the spacer
- H01F10/325—Exchange coupling of magnetic film pairs via a very thin non-magnetic spacer, e.g. by exchange with conduction electrons of the spacer the spacer being noble metal
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F10/00—Thin magnetic films, e.g. of one-domain structure
- H01F10/32—Spin-exchange-coupled multilayers, e.g. nanostructured superlattices
- H01F10/324—Exchange coupling of magnetic film pairs via a very thin non-magnetic spacer, e.g. by exchange with conduction electrons of the spacer
- H01F10/3254—Exchange coupling of magnetic film pairs via a very thin non-magnetic spacer, e.g. by exchange with conduction electrons of the spacer the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F10/00—Thin magnetic films, e.g. of one-domain structure
- H01F10/32—Spin-exchange-coupled multilayers, e.g. nanostructured superlattices
- H01F10/324—Exchange coupling of magnetic film pairs via a very thin non-magnetic spacer, e.g. by exchange with conduction electrons of the spacer
- H01F10/329—Spin-exchange coupled multilayers wherein the magnetisation of the free layer is switched by a spin-polarised current, e.g. spin torque effect
Definitions
- the present invention relates to a magnetoresistive element, and more specifically, to a noncollinear magnetoresistive element having a non-collinear magnetization arrangement.
- a magnetoresistive element (hereinafter simply referred to as an MR element) basically has a three-layer structure, and the structure is composed of a free layer, a fixed layer, and a nonmagnetic layer sandwiched therebetween.
- MR element there are two types of MR elements, one that uses the giant magnetoresistance effect (GMR) and one that uses the tunnel magnetoresistance effect (TMR).
- GMR giant magnetoresistance effect
- TMR tunnel magnetoresistance effect
- the magnetization directions of the free layer and the fixed layer may be parallel or antiparallel, and these are associated with “0” and “1” of the digital signal.
- the MR element is expected as an MRAM (Magnetoresistive Random Access Memory) that replaces DRAM and SRAM that are widely used at present.
- the MR element is expected to be applied as a Gbit-class non-volatile memory because it can be miniaturized.
- Information writing is performed by passing a current (current pulse) in the direction perpendicular to the MR element.
- STT spin transfer torque
- the relative orientation of the magnetization of the free layer and the fixed layer changes from parallel to antiparallel or vice versa.
- Information is read out by utilizing the fact that there is a difference in magnetoresistance (magnetoresistance effect) between parallel and antiparallel.
- the initial MR element has an easy magnetization direction in-plane (in-plane type), but the improved MR element has an easy magnetization direction perpendicular (vertical type).
- the free magnetization and the fixed layer in the same element have the same easy magnetization direction. If the easy magnetization direction of the free layer is perpendicular, the easy magnetization direction of the fixed layer is also perpendicular.
- An MR element in which the free layer and the fixed layer have the same easy magnetization direction is called a collinear MR element.
- Both the free layer and the fixed layer are often composed of ferromagnetic crystals. In that case, the easy magnetization direction is the same as the c-axis which is the crystal axis of the crystal.
- the collinear MR element has a problem that the writing time (switching time) is long.
- the shortest switching time reported is 3 ns (nanoseconds) for a practical device.
- the switching time is required to be as short as 1 ns or less.
- a non-collinear MR element having a non-collinear magnetization arrangement that is, a non-collinear magnetization arrangement
- the proposed non-collinear MR element has a tilted easy magnetization direction (fixed layer), uses an oblique deposition method to obtain the tilt, and has a tilted crystal axis (fixed layer).
- the oblique deposition method is a special method and has a problem that it is difficult to control crystal growth.
- Patent Document 1 proposes the non-collinear MR element, and the MR element has a biaxial anisotropy and “conical anisotropy” is disclosed (for example, paragraph 041 of Patent Document 1). reference).
- Non-collinear MR element disclosed in Patent Document 1 is not specifically disclosed, and does not disclose a non-collinear MR element having a “cone magnetization state” at room temperature.
- An object of the present invention is to provide a non-volatile non-collinear MR element that has a “cone magnetization state” at room temperature and has a storage retention time of 10 years or more for one element (storage unit).
- the non-collinear magnetoresistive element including the nonmagnetic layer sandwiched between the free layer and the pinned layer has the pinned layer having an easy magnetization direction in the in-plane direction or the vertical direction, and is free.
- the non-collinear magnetoresistive element including the nonmagnetic layer sandwiched between the free layer and the pinned layer has the pinned layer having an easy magnetization direction in the in-plane direction or the vertical direction, and free
- E RT (K u1, eff + K u2 + K u1, eff2 / 4K u2 ) ⁇ V
- K u1, eff Effective Primary anisotropy constant
- Ku2 secondary anisotropy constant
- V volume.
- the non-collinear magnetoresistive element is the non-collinear magnetoresistive element according to the first or second aspect, and the free layer preferably has uniaxial anisotropy.
- the non-collinear magnetoresistive element is the non-collinear magnetoresistive element according to any one of the first to third aspects, wherein the free layer includes (1) a thin film containing Co, Pt or It is preferable to include an alternating multilayer film including a thin film containing Pd, (2) a superlattice film containing Co and Pt or Pd, or (3) an alloy thin film containing Co having an hcp structure.
- the easy magnetization direction of the fixed layer may be tilted, but the easy magnetization direction should be tilted with the free layer in the cone magnetization state. This is because the pinned layer wants the magnetization direction to be stable for a longer time than the free layer.
- the free layer is in a cone magnetization state. Therefore, the present inventors paid attention to a non-collinear MR element whose free layer is in a cone magnetization state.
- FIG. 1 shows a longitudinal section of a vertical type non-collinear magnetoresistive element (an example).
- FIG. 2 shows a longitudinal section of an in-plane type non-collinear magnetoresistive element (an example). 1 and 2 indicate the direction in which electrons flow when the current density is positive.
- the description will be given by taking the vertical type element of FIG. 1 as an example, but the same applies to the in-plane type element of FIG.
- FIG. 3 is an explanatory diagram for explaining the cone magnetization state.
- the easy magnetization direction m 0 indicated by the arrow is at some position on the conical surface. Note that the magnetization direction is not rotating. Even if the magnetization (arrow) is reversed, the magnetization direction is on the conical surface.
- the tail or head of the arrow is above the crystal axis (c-axis in FIG. 3). Since this element is a vertical type, the c-axis is the vertical direction (Z-axis).
- the present inventors have found that the non-collinear MR element according to one aspect of the present invention described above, more specifically, the non-collinear MR element according to one embodiment described below achieves the object of the present invention. The present invention has been found.
- FIG. 2 An embodiment of the non-collinear MR element of the present invention will be described.
- a vertical type element will be described as an example.
- the present invention can be applied to the in-plane type (FIG. 2).
- the structure of the element is conceptually shown in FIG.
- This element includes a free layer 1 (upper layer), a fixed layer 3 (lower layer), and a nonmagnetic layer 2 (intermediate layer) sandwiched therebetween.
- the free layer 1 is in a cone magnetization state
- the fixed layer 3 has an easy magnetization direction in the vertical direction.
- each layer of the element of FIG. 1 will be mainly described.
- Free layer of an embodiment of the present invention has 1.66 ⁇ 10 -19 J or more E RT. That is, the free layer satisfies the following formula (1).
- E RT (K u1, eff + K u2 + K u1, eff 2 / 4K u2 ) ⁇ V
- K u1, eff Effective first-order anisotropy constant
- K u2 quadratic anisotropy constant
- V Volume.
- E RT unit: ⁇ 10 ⁇ 19 J
- E RT unit: ⁇ 10 ⁇ 19 J
- E RT large E RT than 1.66 ⁇ 10 -19 J of formula (1) are preferred.
- ERT has a preferable value (range) in the form of “E RT / (k B T)”, this is also shown in Table 1.
- k B is the Boltzmann constant and T is the Kelvin temperature.
- E RT is not prescribed in the present invention, large E RT than necessary is not preferable because it increases the power consumption of the information writing. Rather, E RT can be said is nearer to the lower limit of the formula (1) and Table 1.
- ERT is proportional to the volume V, it is limited by the memory capacity. The larger the capacity / high density memory, the smaller the volume V of one element. Therefore, the free layer according to an embodiment of the present invention satisfies the above formula (1) and the volume V satisfies the following formula (2) in consideration of the case where it is used as a large capacity / high density memory. Is required. V ⁇ 5 ⁇ 10 4 nm 3 (2)
- the cone magnetization state of the free layer will be described with reference to FIGS.
- the magnetization direction of the free layer is defined as m.
- m m 0 .
- the easy magnetization direction m 0 of the free layer is on the conical surface. If an external stimulus such as current or heat is applied to the free layer, m will not stay at m 0 .
- the inclination angle (polar angle) of m is ⁇
- the polar angle of m 0 is ⁇
- the azimuth angle of m is ⁇ m (an arbitrary value).
- FIG. 4 is a coordinate diagram showing a range in which the cone magnetization state is obtained.
- the horizontal arrow in FIG. 4 represents the in-plane magnetization state
- the vertical arrow represents the vertical magnetization state.
- E ( ⁇ ) K u1, eff sin 2 ⁇ + K u2 sin 4 ⁇ (5)
- Ku1, eff Ku1- (1/2) ⁇ 0 M s 2
- Ku1 is a first-order anisotropic constant
- ⁇ 0 is the vacuum permeability
- M s is the saturation magnetization.
- the inclination angle (polar angle) ⁇ 0 of the easy magnetization direction m 0 of the free layer (cone magnetization state) is expressed by the following equation (6), and E ( ⁇ ) expressed by equation (5) is minimized. It is obtained as a value.
- FIG. 5 is a graph for explaining the dependence of the inclination angle (polar angle) ⁇ 0 of the easy magnetization direction m 0 on Ku 1, eff and Ku 2 .
- ⁇ 0 is a decreasing function for Ku1, eff and Ku2 .
- Switching time is larger the inclination angle theta 0 of easy magnetization direction m 0 short.
- the MR ratio of the element decreases as the tilt angle ⁇ 0 increases. Therefore, the reading speed (proportional to the MR ratio) becomes small.
- ⁇ 0 is preferably 0 ° ⁇ 0 ⁇ 45 °, more preferably 5 ° ⁇ 0 ⁇ 30 °, and particularly preferably 10 ° ⁇ 0 ⁇ 20 °. This is the same for the in-plane type (see FIG. 3).
- the magnetic characteristics of the free layer alone may be measured in advance and its Ku1, eff , Ku2 may be confirmed, and then the element may be fabricated using the free layer.
- the present invention is not limited to the fact that the entire free layer is in a cone magnetization state. A part of the free layer may be in a cone magnetization state. For example, by generating interfacial magnetic anisotropy in the free layer near the interface with the nonmagnetic layer or cap layer, and by competing the interfacial magnetic anisotropy with the magnetic anisotropy of the free layer, the cone magnetization state partially You can also get
- the free layer material capable of realizing the cone magnetization state include the following.
- the thin film containing Co preferably has, for example, an hcp crystal or an fcc (111) crystal structure.
- the thin film containing Pt or Pd is preferably, for example, an fcc (111) crystal, but may have other plane orientations.
- the thin film containing Co may be fcc (001), and the thin film containing Pt or Pd may be fcc (001).
- the film thickness of one Co-containing thin film laminated on the Pt-containing thin film preferably corresponds to 10 to 15 Co atoms.
- the film thickness of one Co-containing thin film laminated on the Pd-containing thin film preferably corresponds to 4.5 to 6 Co atoms.
- a multilayer film or a superlattice film made of a thin film containing Co (film thickness: 1.1 nm) laminated on a thin film containing Pt (film thickness: 2 nm) can also be used.
- a superlattice film in which thin films containing Pt having a thickness of about 1 to 2 atomic layers are alternately stacked from several cycles to several tens of cycles can be used.
- Co-thin film (thickness 0.7 nm) / Pd-thin film (thickness 1 nm to 1.5 nm), two layers of multilayer film, or about 1-2 atomic layers of Co thin film and thickness It is also possible to use a superlattice film in which thin films containing about 1-2 atomic layers of Pd are alternately stacked from several cycles to several tens of cycles.
- each value in the tables indicates E RT (unit: ⁇ 10 -19 J) and volume V (unit: nm 3 ) in parentheses ([]) next to it.
- values surrounded by double lines in the table indicate examples of one embodiment of the present invention, and numbers in italics with “*” indicate particularly preferable examples.
- the example of the crystal has been described above. However, if the cone magnetization state can be obtained, the free layer can be a single crystal, polycrystal, partial crystal, texture, nano-crystal, amorphous, A mixed system of
- the free layer thickness is related to volume V, but is also related to other factors. That is, it is preferable that the free layer is thin because the threshold current density is small, but conversely there is a problem that the thermal stability is lowered. Further, when the free layer becomes thin, there is a problem that it is difficult to form a continuous film. On the contrary, when the free layer becomes thick, there arises a problem that magnetization reversal does not occur unless a proportionally large current is passed. Accordingly, the thickness of the free layer is generally about 1 to 10 nm, for example, and preferably about 1 to 3 nm.
- K u1, eff and K u2 is (in the positive direction) and increase "E RT / (k B T)" is increased.
- K u2 must be greater than 107kJ / m 3 in order to meet the "E RT / (k B T)" ⁇ 40.
- the inclination angle ⁇ 0 is 15.8 °.
- the current density of the current applied to the element is J D
- the positive current density J D (> 0) causes electrons to flow from the free layer to the fixed layer.
- K u1, eff is ⁇ 20 kJ / m 3
- K u2 is 135 kJ / m 3
- ⁇ 0 is 15.8 °
- “E RT / (k B T)” is 43.5.
- ⁇ is the gyromagnetic ratio
- M s is the saturation magnetization
- ⁇ is the dimensionless time.
- T sw is 0.67 ns in the first embodiment of the free layer described above.
- T sw reported to be the shortest in the collinear MR element is about 3 ns, for example.
- the switching time T sw (0.67 ns) of one embodiment of the present invention is shortened to about 1/5 (22%) compared to the conventional example (about 3 ns).
- the threshold current density J sw required switching threshold current density J sw (9.46 ⁇ 10 6 A / cm 2) of Example 1, the conventional with the same E RT and V Example 1 Example (13.5 ⁇ 10 Compared to 6 A / cm 2 ), it can be reduced by 22%.
- Nonmagnetic layer The material of the nonmagnetic layer located between the free layer and the fixed layer is already known, but it is divided into (1) nonmagnetic metal (GMR element) and (2) insulator (TMR element). be able to. In the case of a TMR element, the nonmagnetic layer is also called a tunnel barrier layer. In the MR element of one embodiment of the present invention, these conventional materials can be used for the nonmagnetic layer. Specific examples are shown below. (1) In the case of non-magnetic metals For example, metals and alloys containing Cu, Ag, Cr, etc. can be used. The thickness of the nonmagnetic layer is, for example, about 0.3 nm to 10 nm.
- the thickness of the nonmagnetic layer is, for example, about 0.3 nm to 2 nm.
- the fixed layer is a ferromagnetic layer having an easy magnetization axis in the vertical direction (in-plane direction for the in-plane type).
- ferromagnetic materials are already known.
- those conventional materials can be used as the fixed layer. Specific examples are shown below.
- iron-based or iron-based alloys eg, FeCo
- an alloy such as CoPt, CoPd, FePt, or FePd, a multilayer film of these alloy thin films, or an alloy obtained by adding B, Cr, or the like to these alloys can be used.
- heat treatment annealing
- annealing may be performed as is well known.
- the film thickness of the fixed layer is generally 2 to 100 nm, for example, and preferably about 2 to 10 nm thicker than the free layer.
- Each of the above-described layers is very thin and can be produced on a substrate by a vacuum thin film forming technique.
- a vacuum thin film forming technique for example, conventional techniques such as a sputtering method, a vapor deposition method, an MBE method, an ALE method, and a CVD method can be selectively used as appropriate.
- a support layer for supporting the magnetization direction of the extraction electrode layer and the fixed layer, and a support for adjusting the easy magnetization direction of the free layer are supported.
- a layer such as a support layer (read-only layer) or a capping layer that assists in increasing the read signal when reading the magnetization directions of the layers and free layers may be added.
- the non-collinear MR elements of the present invention to which the above electrode layers and the like are added can be arranged in an array, and wiring and additional circuits necessary for writing or reading information can be provided to constitute a magnetic memory.
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Abstract
Description
本発明の目的は、室温で“コーン磁化状態”を持ち、素子1個(記憶単位)について10年以上の記憶保持時間を持つ不揮発性のノンコリニアMR素子を提供することである。
本発明の第2の態様によると、自由層と固定層との間に挟まれた非磁性層を備えるノンコリニア磁気抵抗素子は、固定層が面内方向又は垂直方向に容易磁化方向を持ち、自由層が室温で次の式(1)~(4)、ERT≧1.66×10-19J(1)、V≦5×104nm3(2)、Ku2>-(1/2)Ku1,eff(3)、Ku1,eff<0(4)を満たし、但し、ERT=(Ku1,eff+Ku2+Ku1,eff2/4Ku2)×V、Ku1,eff:実効的な1次の異方性定数、Ku2:2次の異方性定数、V:体積、である。
本発明の第3の態様によると、ノンコリニア磁気抵抗素子は、第1又は第2の態様のノンコリニア磁気抵抗素子であって、自由層が一軸性の異方性を持つことが好ましい。
本発明の第4の態様によると、ノンコリニア磁気抵抗素子は、第1から第3のいずれかの態様のノンコリニア磁気抵抗素子であって、自由層が、(1)Coを含む薄膜と、Pt若しくはPdを含む薄膜との交互多層膜、(2)CoとPt若しくはPdを含む超格子膜、又は(3)hcp構造を有するCoを含む合金薄膜を含むことが好ましい。
理論的には、固定層の容易磁化方向が傾いていてもよいが、自由層をコーン磁化状態として容易磁化方向を傾けるべきである。何故なら、固定層は自由層より長い時間磁化方向が安定していて欲しいからである。因みに、既出の特許文献1では、自由層がコーン磁化状態である。そこで、本発明者らは、自由層がコーン磁化状態のノンコリニアMR素子に着目した。図1に垂直タイプのノンコリニア磁気抵抗素子(一例)の縦断面を示す。図2に面内タイプのノンコリニア磁気抵抗素子(一例)の縦断面を示す。なお、図1、図2の矢印eは、正の電流密度の場合に、電子が流れる方向を示す。以下、図1の垂直タイプの素子を例にとって説明を進めるが、図2の面内タイプの素子でも同様に成り立つ。
Ku2 > -(1/2)Ku1,eff (3)
同時に、本発明者らは、実効的な1次の項(Ku1,eff)が負の材料、即ち、次の式(4)を満たす材料に着目した。
Ku1,eff < 0 (4)
そして、本発明者らは、鋭意研究の結果、上述した本発明の一態様のノンコリニアMR素子、より具体的には以下に説明する一実施形態のノンコリニアMR素子が本発明の目的を達成することを見出し、本発明を成すに至った。
本発明の一実施形態の自由層は、1.66×10-19J以上のERTを持つ。即ち、自由層は、次の式(1)を満たす。
ERT ≧ 1.66×10-19J (1)
但し、ERT = (Ku1,eff+Ku2+Ku1,eff 2/4Ku2)×V、
Ku1,eff:実効的な1次の異方性定数、
Ku2:2次の異方性定数、
V:体積、である
これにより素子1個(1bit)の記憶保持時間が10年以上となる。1つの基板に多数の素子を配置して大容量のメモリを作製する場合、ERTがより大きいことが好ましい。基板(メモリ)全体として記憶保持の保証を考えると、確率の問題で、素子1個については、より大きなERTが好ましい。例えば、256Mbitから16Gbitのメモリについて、好ましいERT(単位:×10-19J)は、下記の表1に示す通りである。ここでは、上記の式(1)の1.66×10-19Jより大きなERTが好ましい。なお、ERTは、「ERT/(kBT)」の形で、好ましい値(範囲)があるので、これについても表1に示す。kBはボルツマン定数であり、Tはケルビン温度である。
V ≦ 5×104nm3 (2)
図1、図3を引用しながら自由層のコーン磁化状態について説明する。自由層の磁化方向をmと定義する。自由層の磁化が容易磁化方向m0を向いている時、m=m0である。自由層の容易磁化方向m0は、円錐面上にある。電流や熱などの外部刺激が自由層に加わると、mがm0に留まらなくなる。mの傾き角(極角)をθ、m0の極角をθ0とし、mの方位角をφm(任意の値)とする。コーン磁化状態となるのは、自由層が一軸性の異方性定数(Ku1,eff , Ku2)が、上述した式(3)及び式(4)を同時に満たす場合である。図4は、コーン磁化状態となる範囲を示す座標図である。コーン磁化状態は、図4において、Ku2 =-(1/2)Ku1,effで表される直線より上側であって、かつ、Ku1,eff =0で表される直線(即ち、縦軸)の左側の領域である。なお、図4の水平方向の矢印は、面内磁化状態を表し、垂直方向の矢印は、垂直磁化状態を表す。
E(θ)=Ku1,effsin2θ+Ku2 sin4θ (5)
但し、Ku1,effは、Ku1,eff=Ku1-(1/2)μ0Ms 2であり、Ku1は1次の異方性定数であり、μ0は真空の透磁率であり、Msは飽和磁化である。自由層(コーン磁化状態)の容易磁化方向m0の傾き角(極角)θ0は、下記の式(6)で表され、式(5)で表されるE(θ)を最小にする値として求まる。
コーン磁化状態を実現できる自由層の材料の具体例としては、例えば以下のものが挙げられる。
(a)Coを含む薄膜とPt若しくはPdを含む薄膜との交互多層膜又は超格子膜
この場合、Coを含む薄膜は例えばhcp結晶又はfcc(111)結晶構造であることが好ましい。Pt若しくはPdを含む薄膜は、例えばfcc(111)結晶であることが好ましいが、他の面方位でもよい。他の例として、Coを含む薄膜はfcc (001)で、Pt若しくはPdを含む薄膜はfcc(001)であってもよい。Ptを含む薄膜の上に積層するCoを含む薄膜1層の膜厚は、Co原子の大きさで10~15個に相当することが好ましい。Pdを含む薄膜の上に積層するCoを含む薄膜1層の膜厚は、Co原子の大きさで4.5~6個に相当することが好ましい。
このようなCo/Pt多層膜及びCo/Pd多層膜について、好ましい例を表2、表3に示す。表2のCo/Pt多層膜は、Ku1,eff=-20kJ/m3、Ku2=135kJ/m3を示すものである。また、表3のCo/Pd多層膜は、Ku1,eff=-10kJ/m3、Ku2=99kJ/m3を示すものである。両表において、表中の各値は、ERT(単位:×10-19J)とその横のかっこ([])内の体積V(単位:nm3)を示している。また、表中の2重線で囲まれた値は、本発明の一実施形態の例を示し、“*”を付けた斜体の数字はその中でも特に好ましい例を示している。以上、材料として結晶の例を説明したが、コーン磁化状態を取れれば、自由層は単結晶、多結晶、部分的結晶、テクスチャー(texture)、微結晶(nano-crystal)、非晶質、それらの混合系でもよい。
自由層の膜厚は体積Vに関連するが、それ以外の因子にも関連がある。すなわち、自由層が薄くなると、閾値電流密度が小さくなるので好ましいが、逆に熱安定性が下がるという問題が発生する。また、自由層が薄くなると、連続膜を作るのが難しくなるという問題も発生する。逆に自由層が厚くなると、それに比例して大きい電流を流さないと磁化反転が起きないという問題が発生する。従って、自由層の膜厚は、一般的には例えば1~10nm程度であり、好ましくは1~3nm程度である。
実施例1として、Co(膜厚0.7nm)/Pt(膜厚1.5nm)の2層膜からなる自由層を挙げる。「ERT/(kBT)」は43.5である。飽和磁化(Ms)は400kA/m、ギルバートダンピング定数(α)は0.04である。真空の透磁率(μ0)は4π×10-7H/m、磁気回転比(γ)は2.21×105rad・m/Aである。この自由層の寸法は、厚さt=2.2nm、直径φ=30nm、体積V=1.56×103nm3である。ERT(=1.80×10-19J) ≧ 1.66×10-19Jであり、体積V ≦ 5×104nm3である。
実施例2として、hcp構造を有するCo合金薄膜からなる自由層を挙げる。寸法は、厚さ=5nm、直径φ=16nm、体積V=1.01×103nm3である。自由層はコーン磁化状態であり、ERT(=1.91×10-19J) ≧ 1.66×10-19Jであり、体積V(1.01×103nm3) ≦ 5×104nm3である。
図6は、室温(T=300ケルビン)における「ERT/(kBT)」のKu1,eff及びKu2の依存性を示す。Ku1,effとKu2が(正の方向に)増加すると「ERT/(kBT)」は増加する。「ERT/(kBT)」≧40を満たすためにKu2は107kJ/m3より大きくなければならない。「ERT/(kBT)」=40となる異方性定数(Ku1,eff,Ku2)が太い点線で示されている。上記した自由層の実施例1では、Ku1,eff=-20kJ/m3でKu2=135kJ/m3である。傾き角θ0は15.8°である。
但し、γは磁気回転比であり、Msは飽和磁化であり、τは無次元化された時間である。τは時間t(s)とτ=γMstの関係にある。
自由層と固定層との間に位置する非磁性層の材料は、既に知られているが、(1)非磁性金属(GMR素子)と(2)絶縁体(TMR素子)に分けることができる。TMR素子の場合、非磁性層はトンネル障壁層とも呼ばれる。本発明の一実施形態のMR素子では、非磁性層これらの従来の材料を用いることができる。以下にその具体例を示す。
(1)非磁性金属の場合
例えばCu、Ag、Crなどを含む金属・合金が使用できる。非磁性層の厚さは、例えば0.3nm~10nm程度である。特に、大きなMR比を実現するCu、Agを含む金属・合金を用いた場合、その厚さは例えば2nm~10nmである。
(2)絶縁体の場合
例えばMg、Al、Si、Ca、Li等の酸化物、窒化物、ハロゲン化物等の様々な誘電体を使用することができる。特に、大きなMR比と小さな面抵抗を両立するMgO(酸化マグネシウム)を使うことが好ましい。酸化物、窒化物を非磁性層に用いる場合は、その酸化物、窒化物の中に酸素、窒素欠損が多少存在していてもかまわない。非磁性層の厚さは、例えば0.3nm~2nm程度である。
固定層は垂直方向(面内タイプの場合は面内方向)に容易磁化軸を持つ強磁性体層である。そのような強磁性体材料は既に知られている。本発明の一実施形態のMR素子では、固定層としてそれらの従来の材料を用いることができる。以下にその具体例を示す。例えば、Fe、Co、Niなどの鉄系又は鉄系合金(例えばFeCo)が代表的な材料である。製法の都合で中間状態としてアモルファス状態を望む場合には、これらにB(ボロン)、Si、Ti、Cr、Vなどを添加した合金FeB、FeCoB、FeCoBSi、FeCoBTi、FeCoBCr、FeCoBVなどを用いることもできる。特に垂直磁化の場合には、CoPt、CoPd、FePt、FePdなどの合金、又はそれらの合金薄膜の多層膜、或いはそれら合金にB、Crなどを添加した合金を用いることができる。アモルファス状態の膜を結晶化するには、良く知られているように例えば熱処理(アニーリング)すれば良い。
上述した各層は、非常に薄いので基板の上に真空薄膜形成技術によって作製できる。そのような技術としては、例えば、スパッタリング法、蒸着法、MBE法、ALE法、CVD法等の従来からある技術を適宜選択的に用いることができる。
日本国特許出願2015年第103909号(2015年5月21日出願)
2:非磁性層
3:固定層
Claims (4)
- 自由層と固定層との間に挟まれた非磁性層を備えるノンコリニア磁気抵抗素子であって、
前記固定層が面内方向又は垂直方向に容易磁化方向を持ち、
前記自由層が室温で下記の式(1)及び(2)を満たし、
ERT ≧ 1.66×10-19J (1)
V ≦ 5×104nm3 (2)
但し、ERT = (Ku1,eff+Ku2+Ku1,eff 2/4Ku2)×V、
Ku1,eff:実効的な1次の異方性定数、
Ku2:2次の異方性定数、
V:体積、
であり、かつコーン磁化状態であるノンコリニア磁気抵抗素子。 - 自由層と固定層との間に挟まれた非磁性層を備えるノンコリニア磁気抵抗素子であって、
前記固定層が面内方向又は垂直方向に容易磁化方向を持ち、
前記自由層が室温で下記の式(1)~(4)を満たし、
ERT ≧ 1.66×10-19J (1)
V ≦ 5×104nm3 (2)
Ku2 > -(1/2)Ku1,eff (3)
Ku1,eff < 0 (4)
但し、ERT = (Ku1,eff+Ku2+Ku1,eff 2/4Ku2)×V、
Ku1,eff:実効的な1次の異方性定数、
Ku2:2次の異方性定数、
V:体積、
であるノンコリニア磁気抵抗素子。 - 前記自由層が一軸性の異方性を持つ請求項1又は2に記載のノンコリニア磁気抵抗素子。
- 前記自由層が、
(1)Coを含む薄膜と、Pt若しくはPdを含む薄膜との交互多層膜、
(2)CoとPt若しくはPdを含む超格子膜、又は
(3)hcp構造を有する Co を含む合金薄膜
を含む請求項1ないし3のいずれか一項に記載のノンコリニア磁気抵抗素子。
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WO2018198713A1 (ja) * | 2017-04-28 | 2018-11-01 | 国立研究開発法人産業技術総合研究所 | 磁気素子 |
CN109564968A (zh) * | 2017-06-20 | 2019-04-02 | 高丽大学校产学协力团 | 具有呈简易圆锥状态的磁性层的磁性隧道结装置 |
JP2020119617A (ja) * | 2019-01-21 | 2020-08-06 | 国立研究開発法人産業技術総合研究所 | 磁気記憶装置 |
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WO2018161146A1 (en) * | 2017-03-10 | 2018-09-13 | Simon Fraser University | Magnetic coupling layers, structures comprising magnetic coupling layers and methods for fabricating and/or using same |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2012104825A (ja) * | 2010-11-05 | 2012-05-31 | Grandis Inc | スイッチングが改良されたハイブリッド磁気トンネル接合要素を提供するための方法およびシステム |
JP2012531747A (ja) * | 2009-06-24 | 2012-12-10 | ニューヨーク ユニヴァーシティー | 電流誘起スピン−運動量移動に基づく高速低電力磁気デバイス |
JP2013021328A (ja) * | 2011-07-07 | 2013-01-31 | Samsung Electronics Co Ltd | 半金属強磁性体を用いた磁気接合を提供するための方法及びシステム |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7604594B2 (en) * | 2004-08-04 | 2009-10-20 | General Electric Company | Method and system of controlling ultrasound systems |
US8374048B2 (en) | 2010-08-11 | 2013-02-12 | Grandis, Inc. | Method and system for providing magnetic tunneling junction elements having a biaxial anisotropy |
US8786039B2 (en) * | 2012-12-20 | 2014-07-22 | Samsung Electronics Co., Ltd. | Method and system for providing magnetic junctions having engineered perpendicular magnetic anisotropy |
US9460397B2 (en) * | 2013-10-04 | 2016-10-04 | Samsung Electronics Co., Ltd. | Quantum computing device spin transfer torque magnetic memory |
US9576633B2 (en) * | 2015-01-05 | 2017-02-21 | Samsung Electronics Co., Ltd. | Method and system for programming magnetic junctions utilizing high frequency magnetic oscillations |
-
2016
- 2016-05-19 WO PCT/JP2016/064924 patent/WO2016186178A1/ja active Application Filing
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Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2012531747A (ja) * | 2009-06-24 | 2012-12-10 | ニューヨーク ユニヴァーシティー | 電流誘起スピン−運動量移動に基づく高速低電力磁気デバイス |
JP2012104825A (ja) * | 2010-11-05 | 2012-05-31 | Grandis Inc | スイッチングが改良されたハイブリッド磁気トンネル接合要素を提供するための方法およびシステム |
JP2013021328A (ja) * | 2011-07-07 | 2013-01-31 | Samsung Electronics Co Ltd | 半金属強磁性体を用いた磁気接合を提供するための方法及びシステム |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2018133422A (ja) * | 2017-02-14 | 2018-08-23 | 国立研究開発法人産業技術総合研究所 | 磁気抵抗素子 |
WO2018198713A1 (ja) * | 2017-04-28 | 2018-11-01 | 国立研究開発法人産業技術総合研究所 | 磁気素子 |
JPWO2018198713A1 (ja) * | 2017-04-28 | 2019-11-07 | 国立研究開発法人産業技術総合研究所 | 磁気素子 |
US10998490B2 (en) | 2017-04-28 | 2021-05-04 | National Institute Of Advanced Industrial Science And Technology | Magnetic element |
CN109564968A (zh) * | 2017-06-20 | 2019-04-02 | 高丽大学校产学协力团 | 具有呈简易圆锥状态的磁性层的磁性隧道结装置 |
CN109564968B (zh) * | 2017-06-20 | 2022-11-29 | 高丽大学校产学协力团 | 磁性隧道结装置及其制造方法 |
JP2020119617A (ja) * | 2019-01-21 | 2020-08-06 | 国立研究開発法人産業技術総合研究所 | 磁気記憶装置 |
JP7246071B2 (ja) | 2019-01-21 | 2023-03-27 | 国立研究開発法人産業技術総合研究所 | 磁気記憶装置 |
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