CN117202760A

CN117202760A - Magnetic tunnel junction memory cell based on magnetic Sjog seed and operation method thereof

Info

Publication number: CN117202760A
Application number: CN202210592202.4A
Authority: CN
Inventors: 于国强; 光耀; 韩秀峰
Original assignee: Institute of Physics of CAS
Current assignee: Institute of Physics of CAS
Priority date: 2022-05-27
Filing date: 2022-05-27
Publication date: 2023-12-08

Abstract

The invention relates to a magnetic tunnel junction memory cell based on magnetic spinelle and an operation method thereof. A magnetic tunnel junction memory cell may include: a reference magnetic layer and a free magnetic layer separated by a barrier layer; a spacer layer separating from the free magnetic layer, the spacer layer inducing ferromagnetic or antiferromagnetic coupling of the spacer layer and the free magnetic layer to each other; and a cap layer formed on the cap layer, the cap layer applying a bias magnetic field to the cap layer by exchange bias such that the cap layer is in a cap phase, wherein the cap layer generates a spin flow when an in-plane write current is applied, the spin flow is vertically injected into the cap layer to write the cap layer, and the cap layer is coupled into the free magnetic layer by ferromagnetic coupling or antiferromagnetic coupling induced by the spacer layer.

Description

Magnetic tunnel junction memory cell based on magnetic Sjog seed and operation method thereof

Technical Field

The invention belongs to the field of magnetic random access memories, and particularly relates to a magnetic tunnel junction memory cell using magnetic spinelle seeds as an information storage carrier and an operation method thereof.

Background

With the advent of the internet of things and the big data age, demands of people for mass data storage, high-energy efficiency and high-speed functional devices are increasing, and the improvement of the storage density of a traditional hard disk faces a series of physical problems such as thermal stability and super-paramagnetic limit. Magnetic spines (Magnetic Skyrmion), abbreviated as spines, are topologically non-trivial chiral spin structures with vortex configuration. Currently, the types of the cassia seeds are generally classified into two types, one is Bloch type (Bloch) cassia seeds which exist in bulk materials and are generated by structural non-central symmetry break, and the other is Neel type (Neel) cassia seeds which exist in thin film materials and are generated by interface inversion symmetry break. Fig. 1 shows schematic diagrams of bloch-type and neled-type stigmas (see left (a) panel) and (see right (b) panel), in which the magnetization direction of the center of the stigmas is vertically downward and the magnetization direction of the periphery of the stigmas is vertically upward. However, the opposite may be the case, i.e. the magnetization direction of the center of the cassia is vertically upward and the magnetization direction of the periphery of the cassia is vertically downward.

The spines have rich material bases, can exist in ferromagnetic materials, ferrimagnetic materials and antiferromagnetic materials, and have the characteristics of small size, high stability, low critical driving current density, low energy consumption, topological non-volatility and the like. In view of these characteristics of the spinodal seed, a technical solution for applying the spinodal seed to the next generation ultra-high density magnetic memory device has been sought. At present, some principle devices such as a spinodal nanooscillator of the spinodal, a shift register of the spinodal and a racetrack memory of the spinodal have been proposed. However, due to limitations in generating, manipulating, deleting, and reading the stigmas, the stigmas have not been successfully applied to magnetic tunnel junctions. Magnetic tunnel junctions are widely used in magnetic storage and magnetic logic devices as classical spintronics devices, so how to more effectively manipulate and read the spinseparator junctions with magnetic tunnel junctions is of great importance for achieving spinseparator-based device applications.

Disclosure of Invention

The present invention has been made in view of the above problems. The present invention provides a novel magnetic tunnel junction structure in which a magnetic free layer and a Stokes sub-carrier layer are coupled to each other and then Stokes sub-information in the carrier layer is determined by reading the magnetoresistance of the magnetic tunnel junction. The magnetic tunnel junction of the present invention can conveniently implement multi-bit storage in a single memory cell and can also be used to perform in-memory calculations.

According to an exemplary embodiment, there is provided a magnetic tunnel junction memory cell including: a reference magnetic layer and a free magnetic layer separated by a barrier layer; a spacer layer separating from the free magnetic layer, the spacer layer inducing ferromagnetic or antiferromagnetic coupling of the spacer layer and the free magnetic layer to each other; and a cap layer formed on the cap layer, the cap layer applying a bias magnetic field to the cap layer by exchange bias such that the cap layer is in a cap phase, wherein the cap layer generates a spin flow when an in-plane write current is applied, the spin flow is vertically injected into the cap layer to write the cap layer, and the cap layer is coupled into the free magnetic layer by ferromagnetic coupling or antiferromagnetic coupling induced by the spacer layer.

In some embodiments, the reference magnetic layer, the free magnetic layer, and the spinodal magnetic exchange layer have perpendicular magnetic anisotropy, and an initial magnetization direction of the free magnetic layer is parallel or antiparallel to a magnetization direction of the reference magnetic layer.

In some embodiments, the spacer layer comprises one or more of Cu, ta, W, pt, ru, hf, ir, au.

In some embodiments, the spinodal support layer comprises one or more of a MnNiGa, mnSi, feCoSi, pt/Co/Ta multilayer film, a Pd/Co/Ta multilayer film, a Pt/Co multilayer film, a Pd/Co multilayer film.

In some embodiments, the capping layer comprises an antiferromagnetic material PtMn, irMn, or AuMn. In some embodiments, the cap layer comprises a layer of ferromagnetic material comprising a multilayer Co, fe, coFeB, pt/Co film, a multilayer Pt/CoFeB film, a multilayer Pd/Co film, or a multilayer Pd/CoFeB film, and an antiferromagnetic coupling layer between the layer of ferromagnetic material and the Sjog seed carrier layer such that the cap layer and the Sjog seed carrier layer form an artificial antiferromagnetic structure, and the antiferromagnetic coupling layer comprises Ta, W, pt, ru, hf, ir or Au.

In some embodiments, the cap layer comprises an artificial antiferromagnetic structure comprising a first ferromagnetic layer and a second ferromagnetic layer separated by an antiferromagnetic coupling layer, wherein the first ferromagnetic layer contacts the sping sub-carrier layer, the first ferromagnetic layer comprises a Pt/Co multilayer film or a Pt/CoFeB multilayer film, and the layer in contact with the sping sub-carrier layer is a Pt layer, the second ferromagnetic layer comprises a Co, fe, coFeB, pt/Co multilayer film, a Pt/CoFeB multilayer film, a Pd/Co multilayer film, or a Pd/CoFeB multilayer film, and the antiferromagnetic coupling layer comprises Cu, ta, W, pt, ru, hf, ir or Au.

In some embodiments, the magnetic tunnel junction memory cell is implemented as a multi-state memory cell, with different memory states corresponding to different numbers of the Sjog dial being written into the Sjog dial carrier layer.

According to another exemplary embodiment, there is provided a method of operating the magnetic tunnel junction memory cell described above, comprising: a writing step including applying an in-plane write current to the cap layer such that the cap layer generates a spin flow by spin hall effect, the spin flow is vertically injected into the spinup sub-carrier layer to write spinup sub-and the spinup sub-is coupled into the free magnetic layer by ferromagnetic coupling or antiferromagnetic coupling generated by the spacer layer; and a reading step comprising applying a vertical read current to the magnetic tunnel junction memory cell to read a resistance of the magnetic tunnel junction memory cell, the resistance of the magnetic tunnel junction memory cell being associated with a number of the Sjog dial bits written into the Sjog dial sub-carrier layer.

In some embodiments, in the writing step, the number of the stigmas written into the stigma seed carrier layer is controlled by controlling a pulse width, a pulse amplitude, and/or a pulse number of the in-plane write current.

In some embodiments, the writing step further includes, prior to applying the in-plane write current, applying an in-plane reset current to the cap layer, the in-plane reset current being opposite to a direction of the in-plane write current to reset the spincell carrier layer to an initial magnetization direction.

In some embodiments, the magnetic tunnel junction memory cell is configured to perform in-memory computing operations comprising: applying a first in-plane write current to the cap layer to write a first amount of the spingy seed to the spingy seed carrier layer; applying a second in-plane write current to the cap layer to write a second amount of the spingy seed to the spingy seed carrier layer; and applying a vertical read current to the magnetic tunnel junction memory cell to read a resistance of the magnetic tunnel junction memory cell, the read resistance corresponding to a third number of Stokes seed, the third number being equal to a sum of the first number and the second number.

The foregoing and other features and advantages of the invention will be apparent from the following description of exemplary embodiments, as illustrated in the accompanying drawings.

Drawings

Fig. 1 shows schematic diagrams of magnetic segetum of the bloch and neel type.

FIG. 2 illustrates a schematic structure of a magnetic tunnel junction memory cell based on magnetic Stokes' semen according to an embodiment of the present invention.

FIGS. 3A and 3B illustrate schematic diagrams of magnetization directions in the magnetic tunnel junction memory cell of FIG. 2 before and after writing a magnetic Sjog seed, respectively, in accordance with an embodiment of the present invention.

FIGS. 4A and 4B illustrate schematic diagrams of magnetization directions in the magnetic tunnel junction memory cell of FIG. 2 before and after writing a magnetic Sjog seed, respectively, in accordance with another embodiment of the present invention.

FIG. 5 shows a schematic diagram of a test sample of a magnetic-Stocket-based magnetic tunnel junction memory cell according to an embodiment of the present invention.

FIG. 6 shows normalized hysteresis loops of perpendicular to the film plane direction of the magnetic tunnel junction memory cell test sample shown in FIG. 5.

FIG. 7 illustrates a schematic diagram of a test device including the Sjog seed magnetic memory cell of FIG. 5, in accordance with one embodiment of the present invention.

FIG. 8 shows the resistance of a 4 μm junction test sample as a function of magnetic field according to an embodiment of the invention.

FIG. 9 shows a photomicrograph of the magnetic domains of the Sjogren carrier layer as a function of magnetic field in a 2 μm junction test sample in accordance with one embodiment of the invention.

FIG. 10 shows a synchronous measurement of the magnetic domain of the Sjog sub-carrier layer and the resistance of the tunnel junction in the 3 μm junction region as a function of magnetic field in accordance with an embodiment of the present invention.

FIG. 11 is a flow chart of a method for performing in-memory calculations using a Sjog seed magnetic memory cell in accordance with an embodiment of the present invention.

Detailed Description

Exemplary embodiments of the present invention are described below with reference to the accompanying drawings.

Fig. 2 illustrates a schematic structure of a magnetic conduction tunnel junction memory cell 100 based on magnetic spinseparator in accordance with an embodiment of the present invention. As shown in fig. 2, the magnetic tunnel junction memory cell 100 includes a seed layer 120, a pinned layer 130, a reference layer 140, a barrier layer 150, a free layer 160, a spacer layer 170, a stopper sub-carrier layer 180, and a cap layer 190, which are sequentially formed on a substrate 110.

The substrate 110 may be an insulating substrate or a conductive (including semiconductor) substrate as desired, examples of commonly used substrate materials may include, but are not limited to, siO ₂ 、MgO、Al ₂ O ₃ Si, siC, plastics, etc.

The seed layer 120, which may also be referred to as a buffer layer, provides a lattice match between the substrate 110 and the overlying magnetic material layer, providing a good growth interface for the magnetic material layer. In some embodiments, seed layer 120 may also serve as a bottom electrode layer, for example when substrate 110 is an insulating substrate. The seed layer 120 may be formed of a single-layer or multi-layer composite film of a non-magnetic metal material having good conductivity and closely bonded to the substrate 110, the material of the seed layer 120 may be selected according to the material of the substrate 110 and the magnetic layer thereon, and the thickness of the seed layer 120 may be selected in a wide range, generally in a range of 1nm to 100nm, preferably in a range of 2nm to 20 nm.

The pinning layer 130 is used to pin the magnetic moment of the reference layer 140 in a predetermined direction so that the magnetic moment direction of the reference layer 140 does not change with a change in the external magnetic field during normal operation. Common pinning layers include antiferromagnetic pinning layers and artificial antiferromagnetic (SAF) structures. The antiferromagnetic pinning layer may be formed of Antiferromagnetic (AFM) material such as IrMn, ptMn, feMn and the like, and its thickness may be in the range of 1 to 30 nm. An artificial antiferromagnetic (SAF) structure comprises a plurality of ferromagnetic metal layers (FM), which may be denoted FM/NM/FM, separated by nonmagnetic metal layers (NM), wherein the nonmagnetic metal layers induce antiferromagnetic (or antiparallel) coupling of the ferromagnetic metal layers on both sides to each other, which ferromagnetic metal layers may comprise a magnetic monolayer or multilayer film structure, and common materials may include, but are not limited to, pt/Co, pt/CoFeB, pd/Co, pd/CoFeB, co, fe, coFeB, etc., typically in the range of 1-20 NM in thickness. Typical materials for the nonmagnetic metal layer may include Cu, cr, nb, ru, pd, ta, W, pt, mo, au or its alloys, typically having a thickness of about 0.2 to 6 nm. In addition, the pinning layer 130 may also employ a ferromagnetic material having a relatively high coercivity, such as a permanent magnet, and the like, which may have a thickness in the range of 1 to 30 nm. In some embodiments, the pinning layer 130 may be omitted, in which case the reference layer 140 may have a self-pinning structure, which will be described in detail below.

The reference layer 140 may comprise a single layer of ferromagnetic metal material, such as Co, fe, coFe, niFe, coFeB, or the like, or may comprise a multi-layer structure of nonmagnetic metal layers and ferromagnetic metal layers, such as Pt/Co, pd/Co, ta/CoFeB, W/CoFeB, ir/CoFeB, pt/CoFeB, or the like. The thickness of the reference layer 140 may be in the range of 1 to 20nm, preferably in the range of 2 to 10 nm. As previously described, the magnetization direction of the reference layer 140 may be fixed in a predetermined direction by the pinned layer 130; when the pinning layer 130 is omitted, the reference layer 140 may have a self-pinning structure, for example, the reference layer 140 is formed of a ferromagnetic material having a relatively high coercivity, or the reference layer 140 may include a multilayer structure of nonmagnetic metal layers and ferromagnetic metal layers as described above, wherein the nonmagnetic metal layers may couple the ferromagnetic metal layers antiparallel to each other, which may reduce the net magnetic moment of the entire reference layer 140, so that the reference layer 140 is less susceptible to external magnetic fields.

The barrier layer 150 may also be referred to as a tunneling layer, which is formed of a non-magnetic insulating material, forming an electron barrier, so that electrons pass through the barrier layer 150 by a tunneling effect, and a tunneling resistance depends on the magnetization directions of the two adjacent ferromagnetic layers. In general, tunneling resistance is minimized when magnetization directions of the two adjacent ferromagnetic layers are parallel to each other; tunneling resistance is maximized when the magnetization directions of the two adjacent ferromagnetic layers are antiparallel to each other. Typical barrier layer materials include metal oxides, e.g. MgO, alO _x 、MgAlO _x Etc. The thickness of the barrier layer 150 may be 0.5 to 6nm, and preferably may be 1 to 4nm.

The free layer 160 may include a single layer of ferromagnetic metal material, for example, a ferromagnetic metal material, or a multi-layer structure of ferromagnetic metal layers and nonmagnetic metal layers. The free layer 160 generally comprises a ferromagnetic material having a relatively small coercivity, such as, but not limited to CoFeB, co, coFe, and the like, which may be 0.5-15 nm thick, preferably 1-10 nm thick.

The layers 110-160 described above, and in particular the core layers 140-160, constitute a conventional magnetic tunnel junction structure, the operation principles of which are known and will not be described in detail herein. It is to be appreciated that the layers 110-160 are not limited to the embodiments described above, but may employ other implementations commonly used in conventional magnetic tunnel junction structures.

The spacer layer 170 may comprise a non-magnetic metallic material, such as a single-layer or multi-layer film structure comprising a non-magnetic metallic material. Examples of nonmagnetic metal materials that may be used for the spacer layer 170 include, but are not limited to Cu, ta, W, pt, ru, hf, ir, au, etc., and the spacer layer 170 may have a thickness of 0.1-10 nm. The spacer layer 170 may use its thickness to modulate RKKY interactions or magnetic dipole interactions between adjacent free layer 160 and the spacer layer 180, inducing ferromagnetic (parallel) or antiferromagnetic (antiparallel) coupling between the free layer 160 and the spacer layer 180.

The carrier layer 180 (or simply carrier layer) of the seeds, as the name implies, can be used to carry (i.e., store) magnetic seeds. The stigmata carrier layer 180 may include a magnetic material capable of storing stigmata, such as a magnetic metal monolayer or a multi-layer film structure of a magnetic metal and a non-magnetic metal, examples of which include, but are not limited to, mnNiGa, mnSi, feCoSi, pt/Co/Ta multi-layer film, pd/Co/Ta multi-layer film, pt/Co multi-layer film, pd/Co multi-layer film, and the like. The thickness of the space seed carrier layer 180 may be 1 to 100nm, preferably 4 to 50nm.

The cap layer 190 formed over the stigman seed carrier layer 180 has multiple functions. In one aspect, the cap layer 190 acts as a top electrode to apply a vertical current through the magnetic tunnel junction; on the other hand, the cap layer 190 functions as a spin injection layer, writing the spiny seeds by injecting a spin flow into the spiny seed carrier layer 180 or erasing the spiny seeds in the carrier layer 180; in yet another aspect, cap layer 190 also functions as a magnetic bias layer that applies a bias magnetic field to the Sjog seed carrier layer 180 to bias the Sjog seed carrier layer 180 in the Sjog seed phase, i.e., in a state in which Sjog seed can be written. The material and structure of cap layer 190 may be designed based on these functional requirements.

In some embodiments, the cap layer 190 may include an antiferromagnetic material having a spin hall effect, such as PtMn, irMn, or AuMn. The antiferromagnetic material may apply the desired bias magnetic field to the Sjog sub-carrier layer 180 by exchange biasing. On the other hand, these antiferromagnetic materials have a spin hall effect, and when an in-plane current is applied, a self-rotational flow is generated, and the spin current is vertically injected into the adjacent stopper sub-carrier layer 180, and a disturbance is generated on the magnetic moment of the stopper sub-carrier layer 180, so that the magnetization direction of a local region can be reversed, thereby forming stopper sub-carriers.

In other embodiments, cap layer 190 may include a layer of ferromagnetic material and an antiferromagnetically coupling layer, and the antiferromagnetically coupling layer is located between the layer of ferromagnetic material and the segmenta carrier layer 180, such that the cap layer 190 (i.e., the layer of ferromagnetic material and the antiferromagnetic coupling layer) forms an artificial antiferromagnetic structure with the segmenta carrier layer 180, wherein the layer of ferromagnetic material provides the desired bias magnetic field to the segmenta carrier layer 180 through antiferromagnetic coupling. Such ferromagnetic material layers may include Co, fe, coFeB, pt/Co multilayer films, pt/CoFeB multilayer films, pd/Co multilayer films, pd/CoFeB multilayer films, or the like, and the antiferromagnetically coupling layer may include a heavy metal material having a spin Hall effect, such as Ta, W, pt, ru, hf, ir or Au, or the like. Thus, when an in-plane current is applied to the cap layer 190, a heavy metal material layer generates a self-rotational flow, and the self-rotational flow is vertically injected into the adjacent stopper seed carrier layer 180, and may disturb the magnetic moment of the stopper seed carrier layer 180, thereby writing stopper seed.

In still other embodiments, the cap layer 190 itself may form an artificial antiferromagnetic structure. For example, the cap layer 190 may include a first ferromagnetic layer and a second ferromagnetic layer separated by an antiferromagnetically coupling layer, which may be the same or different, and may be brought into contact with the Sjog sub-carrier layer 180 for convenience of description. The first ferromagnetic layer may comprise a Pt/Co multilayer film or a Pt/CoFeB multilayer film, and the layer in contact with the spinodal sub-carrier layer 180 is a Pt layer, since Pt is a heavy metal material with spin hall effect, a spin flow injection may be provided to the spinodal sub-carrier layer 180. The second ferromagnetic layer may comprise a Co, fe, coFeB, pt/Co multilayer film, a Pt/CoFeB multilayer film, a Pd/Co multilayer film, a Pd/CoFeB multilayer film, or the like, and the antiferromagnetically coupling layer may comprise Cu, ta, W, pt, ru, hf, ir or Au, or the like. Thus, the artificial antiferromagnetic structure may bias the magnetization direction of the Sjog sub-carrier layer 180 through exchange coupling; on the other hand, when an in-plane current is applied to the artificial antiferromagnetic structure, a heavy metal material layer (e.g., pt layer) in contact with the stopper sub-carrier layer 180 generates a self-rotational flow, and the spin flow is vertically injected into the stopper sub-carrier layer 180, and thus a disturbance may be generated in the magnetic moment of the stopper sub-carrier layer 180, thereby writing stopper sub-carriers.

In the above-described embodiments, the heavy metal material such as Pt, ta, au, W and the like included in the cap layer 190 has good oxidation resistance and electrical conductivity, so that it can be ensured that the underlying layers are not easily corroded by oxidation and moisture, and the cap layer 190 can serve as a top electrode of a magnetic memory cell for applying write and read currents and the like, which will be described in detail below. The thickness of the cap layer 190 may be selected within a wide range depending on the structure it has, and is generally in the range of 1nm to 100nm, preferably in the range of 1nm to 20 nm. In addition to writing the cassia seed to the cassia seed carrier layer 180 using the cap layer 190, the cassia seed in the cassia seed carrier layer 180 may be erased by controlling the direction of the in-plane current applied to the cap layer 190 and applying a self-rotational flow in the opposite direction to the cassia seed carrier layer 180, the operation of writing and erasing the cassia seed being described in further detail below in connection with the arrangement of the magnetization directions of the respective layers.

Fig. 3A and 3B show schematic diagrams of the magnetization directions of the respective magnetic layers in the magnetic tunnel junction memory cell 100 before and after writing the magnetic spines, respectively. In this embodiment, the pinned layer 130, the reference layer 140, the free layer 160, and the spinodal carrier layer 180 have perpendicular magnetic anisotropy, i.e., the easy axis of magnetization is in the perpendicular direction, rather than in the in-plane direction. It should be understood that these magnetization directions are merely examples, and that the various magnetic layers may also be configured to have different magnetization directions without departing from the principles of the present invention.

Referring first to fig. 3A, the pinning layer 130 employs an artificial antiferromagnetic (SAF) structure comprising a first ferromagnetic layer 132 and a second ferromagnetic layer 136 separated by a nonmagnetic metal layer 134, and the first ferromagnetic layer 132 and the second ferromagnetic layer 136 are antiferromagnetically coupled to each other. In this example, the first ferromagnetic layer 132 has a vertically downward magnetization direction and the second ferromagnetic layer 136 has a vertically upward magnetization direction, but other configurations may be employed, such as the first ferromagnetic layer 132 having a vertically upward magnetization direction and the second ferromagnetic layer 136 having a vertically downward magnetization direction.

The reference layer 140 may be ferromagnetically coupled with the second ferromagnetic layer 136 in the artificial antiferromagnetic structure 130 so as to also have a magnetization direction that is vertically upward in this example.

The initial magnetization direction of the free layer 160 (the magnetization direction when no stigmine is written) may be oriented parallel or antiparallel to the reference layer 140 such that the resistance of the magnetic tunnel junction 100 is either minimum (corresponding to the parallel state) or maximum (corresponding to the antiparallel state). In the example shown in FIG. 3A, the initial magnetization direction of the free layer 160 is antiparallel, i.e., vertically downward, to the reference layer 140. It will be appreciated that the magnetic tunnel junction memory cell of the present invention also has improved magnetic stability because the spacer layer 170 either ferromagnetically couples or antiferromagnetically couples the free layer 160 to the Sjog sub-carrier layer 180, and thus the direction of magnetization of the free layer 160 can change in response to a change in magnetic moment in the Yu Sige sub-carrier layer 180, but can resist to some extent (depending on the coupling strength induced by the spacer layer 170) a change in external magnetic field.

The space layer 170 may be ferromagnetically or antiferromagnetically coupled to the free layer 160 by the space layer 180, in the example shown in FIG. 3A, with the direction of magnetization of the space layer 180 being parallel to the direction of magnetization of the free layer 160, i.e., vertically downward. In the case of antiferromagnetic coupling, the magnetization of the Sjogren layer 180 is antiparallel to the magnetization of the free layer 160, i.e., vertically upward.

It will be appreciated that the resistance of the magnetic tunnel junction 100 is primarily dependent on the magnetization directions of the reference layer 140 and the free layer 160 on either side of the barrier layer 150, with the minimum resistance when coupled in parallel and the maximum resistance when coupled antiparallel. Since the spacer layer 170 and the nonmagnetic metal layer 134 are both formed of a conductive metal material, the ferromagnetic and antiferromagnetic coupling of the magnetization directions of the ferromagnetic layers on both sides thereof affects the resistance of the magnetic tunnel junction 100 due to Giant Magnetoresistance (GMR) effect, but this effect is very small for perpendicular read currents and negligible.

As previously described, when an in-plane current is applied to cap layer 190, it produces a self-rotational flow through the spin Hall effect that is injected vertically into the Sjog sub-carrier layer 180. By controlling the direction of the in-plane current applied to the cap layer 190, the spin polarization direction of the generated spin flow can be controlled. For example, when an in-plane current (i.e., an in-plane write current) has a first direction, the resulting spin current can flip the local magnetic moment of the Sjog sub-carrier layer 180, thereby writing to the Sjog sub. FIG. 3B illustrates the magnetization orientation when writing the Sjogren in the magnetic tunnel junction memory cell 100 shown in FIG. 3A, wherein the thick arrow in the Sjogren sub-carrier layer 180 represents the initial magnetization direction and the thin arrow represents the written direction of the Sjogren's magnetization (or the direction of the magnetization of the center region of the Sjogren), which is coupled into the free layer 160 by a coupling induced by the spacer layer 170 (ferromagnetic coupling in the illustrated example), thereby changing the local magnetization direction of the free layer 160. It can be appreciated that in the initial state, the magnetic moments of the free layer 160 and the reference layer 140 are antiparallel, and the tunneling resistance is maximized; as more of the sigma-delta is written, the magnetic moment of more of the free layer 160 will be flipped to be parallel to the magnetic moment of the reference layer 140, and thus the tunneling resistance of the magnetic tunnel junction will decrease. By measuring the tunneling resistance of the magnetic tunnel junction, the number of written stigmas can be determined, and thus the information stored in the magnetic tunnel junction memory cell.

On the other hand, when the in-plane current (i.e., in-plane reset current) applied to the cap layer 190 is in the opposite direction to the in-plane write current, the spin polarization direction of the generated spin current is opposite to the spin polarization direction generated by the write current, so that the stinger seed in the stinger seed carrier layer 180 can be erased, the stinger seed carrier layer 180 can be reset to the initial magnetization direction, and the free layer 160 can be also reset to the initial magnetization direction by the coupling induced by the spacer layer 170, as shown in fig. 3A.

Fig. 4A and 4B illustrate schematic diagrams of magnetization directions of respective magnetic layers in the magnetic tunnel junction memory cell 100 before and after writing a magnetic spinelle, respectively, according to another exemplary embodiment. The examples shown in fig. 4A and 4B are identical in many respects to the examples shown in fig. 3A and 3B, and repeated descriptions of the same portions will be omitted herein, and only different portions will be described.

Referring first to fig. 4A, unlike the example of fig. 3A, the initial magnetization direction of the free layer 160 and the reference layer 140 are parallel to each other, and thus the magnetic tunnel junction has the smallest tunneling resistance. The spacer layer 170 induces antiferromagnetic coupling so that the magnetic moment of the Sjog sub-carrier layer 180 is antiparallel to the free layer 160.

Referring to FIG. 4B, by controlling the direction of the in-plane write current applied to cap layer 190, a Sjog seed can be written into Sjog seed carrier layer 180, shown in FIG. 4B by the thin upward pointing arrow, and coupled into free layer 160 by the antiferromagnetic coupling induced by spacer layer 170, as shown by the thin downward pointing arrow in free layer 160. It will be appreciated that in the initial state, the magnetic moments of the free layer 160 and the reference layer 140 are parallel to each other, with minimal tunneling resistance; as more of the sigma-delta is written, the magnetic moment of more of the free layer 160 will be flipped antiparallel to the magnetic moment of the reference layer 140, and thus the tunneling resistance of the magnetic tunnel junction will increase. By measuring the tunneling resistance of the magnetic tunnel junction, the number of written stigmas can be determined, and thus the information stored in the magnetic tunnel junction memory cell.

Fig. 5 shows a schematic structural diagram of a magnetic tunnel junction memory cell sample based on magnetic spinseparator according to an embodiment of the invention, where (a) is a schematic hierarchical structure and (b) is a photomicrograph of a cross section. As shown in fig. 5, the sample includes the following layer structure in order from the substrate 110 (not shown): ta (2)/Ru (5)/Pt (2)/[ Co (0.28)/Pt (0.16) ] ₉ /Co(0.28)/Ru(0.4)/Co(0.28)/[Pt(0.16)/Co(0.28)] ₅ /Ta(0.2)/Co ₄₀ Fe ₄₀ B ₂₀ (0.8)/MgO(2.5)/Co ₂₀ Fe ₆₀ B ₂₀ (1.2,1.3,1.4 or 1.5)/Ta (2)/[ Pt (3)/Co (2)/Ta (2)] ₁₀ The values in parentheses indicate the thickness in nm, the brackets indicate the unit structure of the multilayer film, and the subscripts of the brackets indicate the number of repetitions. It will be appreciated that in this sample, ta (2)/Ru (5) was used as the seed layer 120 and the pinning layer 130 comprised an artificial antiferromagnetic (SAF) structure in which the first and second ferromagnetic layers 132/136 were Pt/Co multilayer films and the nonmagnetic metal layer 134 was 0.4nm thick Ru on which a 0.2nm thick Ta layer was used as a buffer layer to facilitate the growth of a 0.8nm thick CoFeB layer with perpendicular magnetocrystalline anisotropy as the reference layer 140. The barrier layer 150 was 2.5nm thick MgO, the free layer 160 was CoFeB, and multiple samples with thicknesses of 1.2nm, 1.3nm, 1.4nm, and 1.5nm were prepared. Spacer layer 170 is a 2nm thick Ta layer and the Sjog seed support layer 180 is a Pt/Co/Ta multilayer film. Here, to measure the magnetic domains of the Sjog seed carrier layer 180 to illustrate the principles of the present invention, the cap layer 190 uses a 2nm Pt layer without using a bias structure, measured belowInstead of the bias magnetic field applied by cap layer 190 to the singe sub-carrier layer 180, an external magnetic field generated by a measuring device may be used.

FIG. 6 shows the normalized hysteresis loop of the perpendicular to film plane direction for the magnetic tunnel junction memory cell sample shown in FIG. 5, where the abscissa represents the external magnetic field H and the ordinate represents the magnetic moment M normalized with respect to the saturation magnetic moment (Ms). In the test sample, the free layer 160 has a thickness of 1.2nm, and the Sjogren carrier layer 180 (Pt/Co/Ta) is ferromagnetically coupled to the free layer 160 (CoFeB), with the Sjogren in each magnetic layer being coupled together by interlayer coupling. The magnetic moment distribution of the magnetic layer in the hysteresis loop of fig. 6 over different magnetic field ranges is indicated with three vertical arrows, which correspond to the three arrows in the left graph (a) of fig. 5, respectively.

Referring to fig. 6, when the external magnetic field H is about zero, the magnetic moments of the two ferromagnetic layers of the artificial antiferromagnetic pinning layer 130 are antiparallel to each other, the magnetic moment of the first ferromagnetic layer 132 is vertically downward, and the magnetic moment of the second ferromagnetic layer 136 is vertically upward. The Sjog sub-carrier layer 180 is in a multi-domain phase with upward and downward magnetic moments. When the external magnetic field H is gradually increased (in either the positive or negative direction), the magnetic domains of the segetum carrier layer 180 are gradually oriented in the direction of the external magnetic field H, so the total magnetic moment M gradually increases with the external magnetic field H. In the vicinity of H = ±2kOe, the domains of the seg sub-carrier layer 180 are all oriented in the direction of the external magnetic field H, when the external magnetic field H increases from about ±2kOe to about ±6kOe, at which time the external magnetic field H is insufficient to overcome the antiferromagnetic coupling induced by the nonmagnetic metal layer 134, the magnetic moments of the first ferromagnetic layer 132 and the second ferromagnetic layer 134 remain unchanged, and thus the total magnetic moment M remains substantially unchanged within the range of the external magnetic field H. As the external magnetic field H continues to increase, it overcomes the antiferromagnetic coupling induced by the nonmagnetic metal layer 134, gradually orienting the magnetic moment of the first ferromagnetic layer 132 or the second ferromagnetic layer 134 in the same direction as the external magnetic field H, at which point the total magnetic moment M gradually increases. When the external magnetic field H reaches about ±8kOe, the magnetic moments of the first ferromagnetic layer 132, the second ferromagnetic layer 134, and the seg-sub-carrier layer 180 are all oriented in the same direction as the external magnetic field H, at which time the total magnetic moment M reaches the saturated magnetic moment Ms, which remains unchanged even if the external magnetic field H continues to increase.

FIG. 7 shows a schematic diagram of a test device for a Sjog seed magnetic memory cell in accordance with an embodiment of the present invention. In fig. 7, the lateral electrode is the bottom electrode, the longitudinal electrode is the top electrode, the width of the current path is 50 μm, the region where the lateral and longitudinal current paths meet contains a single magnetic tunnel junction, and the junction region size (e.g., the diameter of the circular junction region) can be processed to be 0.1 μm to 10 μm unequal. Reference numerals 1-12 correspond to electrode numbers, e.g. V ₁₃ Representing the voltages measured at electrodes 1 and 3, I ₂₄ Representing the current applied across electrodes 2 and 4, through V ₁₃ And I ₂₄ The tunneling resistance of the magnetic tunnel junction at the junction of the current channels connecting the electrodes 1, 2 and 3, 4 can be measured.

FIG. 8 is a plot of tunneling resistance R of a magnetic tunnel junction sample having a junction area size of 4 μm as a function of external magnetic field H perpendicular to the film plane. As can be seen from the left plot of fig. 8, the variation of the tunneling resistance R with the external magnetic field H corresponds to the hysteresis loop described above with respect to fig. 6, with the high and low resistance states respectively aligned antiparallel and parallel to the magnetic moments of the ferromagnetic layers on either side of the barrier layer, wherein the magnetic moment of the reference layer 140 is parallel to the magnetic moment of the second ferromagnetic layer 136 in the artificial antiferromagnetic structure 130 and the magnetic moment of the free layer 160 is parallel to the magnetic moment of the segrain carrier layer 180.

The right graph of fig. 8 shows that after saturation magnetization is reached by the perpendicular magnetic field H of-1T, the external magnetic field H is reduced to-2 kOe, and then the loop of the tunneling resistance R in the range of-2 kOe to +2kOe external magnetic field is measured, whereby the Tunneling Magnetoresistance (TMR) is calculated to be about 18.5%. Also noted in the right hand diagram of fig. 8 are three states (i.e., the "phases") of the sigma subcarrier layer 180, namely multi-domain, sigma substate, and single domain states, which will be described in further detail below.

Fig. 9 is a photomicrograph of the magnetic domains of the stopper sub-carrier layer 180 in a magnetic tunnel junction having a junction area size of 2 μm as a function of the external magnetic field H in the vertical direction, wherein the magnetic domains are measured using a magnetic force microscope. Referring to fig. 9, when the external magnetic field H is zero, the singe sub-carrier layer 180 is in a multi-domain state; when the external magnetic field H is increased to 1082Oe, obvious multi-domain and Sjog seed coexistence states appear; as the external magnetic field H continues to increase, e.g. at 1236Oe and 1623Oe, the spiny seed carrier layer 180 assumes a spiny seed state (otherwise referred to as a spiny seed phase) in which a plurality of spiny seeds are stably stored; as the external magnetic field H continues to increase, the cassia seed in the cassia seed carrier layer 180 gradually disappears, and when the external magnetic field H reaches 1700Oe, the cassia seed completely disappears, and the cassia seed carrier layer 180 assumes a single domain state. As can be seen from the measurement result of fig. 9, the stopper sub-carrier layer 180 may be in a state of stably storing stopper sub-carriers when a predetermined bias magnetic field is applied. Although the measurement data on the sample indicate that [ Pt (3)/Co (2)/Ta (2) is made ] ₁₀ The magnitude of the bias magnetic field of the space seed carrier layer 180 in the space seed phase is approximately in the range of 1150Oe to 1650Oe, but further theoretical analysis and experimental data indicate that the magnitude of the required bias magnetic field varies depending on factors such as the material selection, thickness, and magnitude of magnetocrystalline anisotropy energy of the space seed carrier layer 180, and thus the present invention is not limited thereto, but can be determined according to actual needs by those skilled in the art under the teaching of the present invention.

FIG. 10 is a plot of simultaneous measurements of the resistance of a magnetic tunnel junction and the magnetic domain of a Sjog sub-carrier layer for a 3 μm junction region as a function of external magnetic field. Referring to fig. 10, it can be seen that when the external magnetic field H increases from zero to 1.1kOe, the space sub-carrier layer 180 is changed from the multi-domain state to the space sub-state, in which 13 space sub-states are present; when entering the single domain state from the spinodal state (external magnetic field H of 1.6 kOe), the resistance of the magnetic tunnel junction is reduced by about 10%. When the external magnetic field H drops from 1.6kOe to 1.1kOe, the Sjog seed carrier layer 180 remains in a monodomain state due to the lack of magnetic moment perturbation, wherein no Sjog seed is present. The external magnetic field H drops all the way to 0.4kOe and the segrain carrier layer 180 reverts to multi-domain. When the external magnetic field H increases again to 1.1kOe, the cassia seed carrier layer 180 assumes a cassia seed state, at which 9 cassia seeds are present. When the external magnetic field H increases to about 1.6koe,9 of the singes disappear, and the singe sub-carrier layer 180 assumes a monodomain state. The measurement results of fig. 10 show that the state of the stopper carrier layer 180 is stably stored by a predetermined external magnetic field H, and the stopper significantly changes the resistance of the Magnetic Tunnel Junction (MTJ) compared to the single domain state (having substantially constant resistance, see c, d, and g in fig. 10), and the resistance change caused by a single stopper can be estimated to be about 50Ω for the sample.

In addition, for the magnetic tunnel junction sample described above, current I may be applied using, for example, electrodes 3 and 4 shown in FIG. 7 when the Sjogren carrier layer 180 is in the Sjogren phase ₃₄ Torque is applied to the magnetic moment in the stopper carrier layer 180 by the self-swirling flow generated by Pt of the top cap layer 190, and a desired number of stopper or stopper is written or erased by controlling the direction and magnitude of the current.

The following discusses a method of operating the magnetic tunnel junction memory cell 100 based on a Sjog dial, which basically includes a writing step and a reading step.

The writing step includes applying an in-plane write current to cap layer 190 such that cap layer 190 generates a spin flow through the spin hall effect and the spin flow is vertically injected into adjacent spingauge seed carrier layer 180. At this time, the stopper sub-carrier layer 180 is in the stopper sub-phase due to the bias magnetic field applied by the cap layer 190, so the injected self-rotational flow can be written into the stopper sub-carrier layer 180, and the stopper sub-carrier layer 180 is coupled into the free layer 160 by the ferromagnetic coupling or antiferromagnetic coupling generated by the spacer layer 170. The amount of the sigma seed written into the sigma seed sub-carrier layer 180 may be controlled by controlling, for example, the pulse width, the pulse amplitude, and/or the number of pulses of the in-plane write current.

It will be appreciated that previously written spinners may be stored in the spinners seed carrier layer 180, and thus a reset operation may be performed before an in-plane write current is applied to write a new spinners seed, applying an in-plane reset current to the cap layer 190 opposite the in-plane write current direction to erase the spinners seed present in the spinners seed carrier layer 180 to the original magnetization direction.

The reading step may include applying a vertical read current to the magnetic tunnel junction memory cell 100 to read the resistance of the magnetic tunnel junction memory cell 100. As previously described, the resistance of the magnetic tunnel junction memory cell 100 is related to the number of Stokes that are written into the Stokes sub-carrier layer 180. For example, in an initial state, the magnetic tunnel junction memory cell 100 may have a minimum or maximum resistance, depending on whether the magnetic moments of the free layer 160 and the reference layer 140 are in a parallel or anti-parallel state, and the resistance of the magnetic tunnel junction memory cell 100 may increase or decrease as the number of the Sjog seeds written into the Sjog sub-carrier layer 180 increases.

It will be appreciated that in some embodiments, the magnetic tunnel junction memory cell 100 may be implemented as a conventional two-state memory, i.e., storing data "0" and "1", where one state corresponds to a state when no stigmine is stored and the other state corresponds to a state when a stigmine is stored (preferably a plurality of stigmine is stored). In other embodiments, the magnetic tunnel junction memory cell 100 may also be implemented as a multi-state memory, i.e., in addition to "0" and "1," there may be "2", "3", "4" or more data stored in a single magnetic tunnel junction memory cell 100, where different memory states correspond to different numbers (also encompassing a range of numbers) of the Sjog dial stored in the Sjog dial layer. For example, data "0" is stored when no sterculia seeds are present in the sterculia seed carrier layer 180, data "1" is stored when Y1 (or X1 to X2) sterculia seeds are present, data "2" is stored when Y2 (or X3 to X4) sterculia seeds are present, and so on. Thus, the magnetic tunnel junction memory cell 100 may store more data information than a conventional two-state memory cell.

According to an embodiment, the magnetic tunnel junction memory cell 100 may also be configured to perform in-memory computation operations, which may omit adders, with addition operations being completed by read and write operations to the memory. FIG. 11 illustrates a flow chart of a method 200 of performing in-memory calculations using the magnetic tunnel junction memory cell 100. Referring to FIG. 11, at step 210, a first in-plane write current may be applied to cap layer 190 to write a first number M of Style seeds to Style sub-carrier layer 180. As previously described, the amount of the Sjog seed written into the Sjog seed carrier layer 180 may be controlled by controlling, for example, the pulse width, the pulse amplitude, and/or the number of pulses of the in-plane write current. At step 220, a second in-plane write current may be applied to cap layer 190 to write a second number N of the Sjog's seeds to the Sjog's seed carrier layer, M and N may be the same or different non-negative integers. At this time, since M number of the cassia seeds have been previously written, q=m+n number of the cassia seeds will exist in the cassia seed carrier layer 180. Then, a vertical read current is applied to the magnetic tunnel junction memory cell 100 to read the resistance of the magnetic tunnel junction memory cell 100, and the number Q of the stopper bits stored therein can be determined based on the read resistance, thereby completing the in-memory calculation of q=m+n.

Although magnetic tunnel junction memory cells are described above, it is understood that the memory may include an array of multiple rows and columns of magnetic tunnel junction memory cells, with multiple word lines, bit lines, power lines, switching transistors, and the like being configured for the array. The array arrangement of such memory cells is known and will not be described in detail here.

Throughout the specification and claims, unless the context clearly requires otherwise, the words "comprise", "comprising", and the like, should be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in a sense of "including but not limited to". Also, the words "herein," "above," "below," and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. The words in the above description using the singular or plural number may also include the plural or singular number, respectively, where the context allows. With respect to the phrase "or" when referring to a list of two or more items, the phrase encompasses all of the following interpretations of the phrase: any item in the list, all items in the list, and any combination of items in the list.

The above detailed description of embodiments of the application is not intended to be exhaustive or to limit the application to the precise form disclosed above. While specific embodiments of, and examples for, the application are described above for illustrative purposes, various equivalent modifications are possible within the scope of the application, as those skilled in the relevant art will recognize. For example, although processes or blocks are presented in a given order, alternative embodiments may perform processes with the steps in a different order or employ systems with the blocks in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and/or modified. Each of these processes or blocks may be implemented in a variety of different ways. In addition, although processes or blocks are sometimes shown as being performed serially, alternatively, these processes or blocks may be performed in parallel, or may be performed at different times.

The teachings of the present application provided herein may be applied to other systems, not necessarily the systems described above. The elements and acts of the various embodiments described above can be combined to provide further embodiments.

While some embodiments of the present application have been described, these embodiments are presented by way of example only and are not intended to limit the scope of the application. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms. In addition, various omissions, substitutions, and changes in the form of the methods and systems described herein may be made without departing from the scope of the application.

Claims

1. A magnetic tunnel junction memory cell comprising:

a reference magnetic layer and a free magnetic layer separated by a barrier layer;

a spacer layer separating from the free magnetic layer, the spacer layer inducing ferromagnetic or antiferromagnetic coupling of the spacer layer and the free magnetic layer to each other; and

a cap layer formed on the said Sjog seed carrier layer, said cap layer applying a bias magnetic field to the said Sjog seed carrier layer by exchange bias such that the said Sjog seed carrier layer is in the Sjog seed phase,

wherein the cap layer generates a spin flow when an in-plane write current is applied, the spin flow is perpendicularly injected into the Sjog carrier layer to write the Sjog, and the Sjog is coupled into the free magnetic layer by ferromagnetic coupling or antiferromagnetic coupling induced by the spacer layer.

2. The magnetic tunnel junction memory cell of claim 1 wherein the reference magnetic layer, the free magnetic layer, and the segrain sub-carrier layer have perpendicular magnetic anisotropy, an initial magnetization direction of the free magnetic layer being parallel or antiparallel to a magnetization direction of the reference magnetic layer.

3. The magnetic tunnel junction memory cell of claim 1 wherein the spacer layer comprises one or more of Cu, ta, W, pt, ru, hf, ir, au.

4. The magnetic tunnel junction memory cell of claim 1 wherein the spinodal carrier layer comprises one or more of a MnNiGa, mnSi, feCoSi, pt/Co/Ta multilayer film, a Pd/Co/Ta multilayer film, a Pt/Co multilayer film, a Pd/Co multilayer film.

5. The magnetic tunnel junction memory cell of claim 1 wherein the cap layer comprises an antiferromagnetic material PtMn, irMn or AuMn, or

The cap layer comprises a ferromagnetic material layer and an antiferromagnetic coupling layer between the ferromagnetic material layer and the Sjog carrier layer, such that the cap layer and the Sjog carrier layer form an artificial antiferromagnetic structure, the ferromagnetic material layer comprises a Co, fe, coFeB, pt/Co multilayer film, a Pt/CoFeB multilayer film, a Pd/Co multilayer film, or a Pd/CoFeB multilayer film, the antiferromagnetic coupling layer comprises Ta, W, pt, ru, hf, ir or Au, or

The cap layer includes an artificial antiferromagnetic structure including a first ferromagnetic layer and a second ferromagnetic layer separated by an antiferromagnetic coupling layer, wherein the first ferromagnetic layer contacts the spinelle sub-carrier layer, the first ferromagnetic layer includes a Pt/Co multilayer film or a Pt/CoFeB multilayer film, and the layer in contact with the spinelle sub-carrier layer is a Pt layer, the second ferromagnetic layer includes a Co, fe, coFeB, pt/Co multilayer film, a Pt/CoFeB multilayer film, a Pd/Co multilayer film, or a Pd/CoFeB multilayer film, and the antiferromagnetic coupling layer includes Cu, ta, W, pt, ru, hf, ir or Au.

6. The magnetic tunnel junction memory cell of claim 1 wherein the magnetic tunnel junction memory cell is implemented as a multi-state memory cell, different memory states corresponding to different numbers of stratospheres written into the stratosphere.

7. A method of operating the magnetic tunnel junction memory cell of any one of claims 1 to 6 comprising:

a writing step including applying an in-plane write current to the cap layer such that the cap layer generates a spin flow by spin hall effect, the spin flow is vertically injected into the spinup sub-carrier layer to write spinup sub-and the spinup sub-is coupled into the free magnetic layer by ferromagnetic coupling or antiferromagnetic coupling generated by the spacer layer; and

a reading step comprising applying a vertical read current to the magnetic tunnel junction memory cell to read a resistance of the magnetic tunnel junction memory cell, the resistance of the magnetic tunnel junction memory cell being associated with a number of the Sjog dial bits written into the Sjog dial carrier layer.

8. The method of claim 7, wherein in the writing step, the number of the cassia seeds written into the cassia seed carrier layer is controlled by controlling a pulse width, a pulse amplitude, and/or a pulse number of the in-plane write current.

9. The method of claim 7, wherein the writing step further comprises, prior to applying the in-plane write current, applying an in-plane reset current to the cap layer, the in-plane reset current being opposite to a direction of the in-plane write current to reset the sigma sub-carrier layer to an initial magnetization direction.

10. The method of claim 7, wherein the magnetic tunnel junction memory cell is configured to perform in-memory computing operations comprising:

applying a first in-plane write current to the cap layer to write a first amount of the spingy seed to the spingy seed carrier layer;

applying a second in-plane write current to the cap layer to write a second amount of the spingy seed to the spingy seed carrier layer; and

applying a vertical read current to the magnetic tunnel junction memory cell to read a resistance of the magnetic tunnel junction memory cell, the read resistance corresponding to a third number of Stokes, the third number being equal to a sum of the first number and the second number.