A neuron device based on spin-orbit torque

Abstract

The present disclosure provides a neuron device based on spin-orbit moment, comprising: an antiferromagnetic pinning layer, a first ferromagnetic layer, and a spin-orbit coupling layer sequentially formed on a substrate; a free layer formed on the spin-orbit coupling layer and capable of moving magnetic domain walls according to the spin-orbit moment; a tunneling layer formed on the free layer; a left pinning layer and a right pinning layer formed on either side of the free layer and having opposite magnetization directions; and a reference layer formed on the tunneling layer. The free layer, the tunneling layer, and the reference layer form a magnetic tunnel junction, which is used to read neuron signals. The present disclosure also provides a method for fabricating a neuron device based on spin-orbit moment.

Description

Technical Field

[0001] The present disclosure relates to the field of brain-like computing technology, and in particular to a neuron device based on spin-orbit moment. Background Art

[0002] Brain-inspired neuromorphic computing is a promising approach to addressing the memory issues inherent in von Neumann architectures and the end of Moore's Law in the post-Moore era. Neuromorphic computing promises to significantly reduce power consumption while further increasing chip computing power.

[0003] The development of neuromorphic computing begins with the study of neuromorphic devices (synapses, neurons, etc.) that possess biological properties. In recent years, researchers have discovered that novel memory devices (magnetic, resistive, phase-change, and ferroelectric) and novel device principles (ion transistors) can better and more comprehensively simulate the characteristics of human brain synapses and neurons than traditional, power-hungry, and expensive CMOS neuron circuits. Magnetic memory's high speed, durability, and low power consumption make it highly competitive in the field of neuromorphic computing.

[0004] However, current research on neuromorphic devices based on spintronics has largely focused on synaptic devices, with relatively little research on neuronal devices. Furthermore, the few neuronal devices that remain all mimic the accumulation characteristics of neurons by using spin-orbit moment-driven magnetic domain wall motion. However, the speed of spin-orbit moment-driven magnetic domain wall motion is slower than that of spin-orbit moment-driven methods. The leakage characteristics of neurons are achieved through shape anisotropy, bias fields, and anisotropy gradients.

[0005] Therefore, in order to be suitable for high-speed and complex neural networks, it is necessary to explore neuronal devices in which spin-orbit torque drives the motion of magnetic domain walls and to simulate the leakage characteristics of neurons through more mechanisms. Summary of the Invention

[0006] In order to solve the above-mentioned problems in the prior art, the present disclosure provides a neuron device based on spin-orbit moment, which aims to solve the accumulation, leakage and discharge characteristics of biological neurons simulated based on magnetic tunnel junctions, and realizes domain wall pinning by depositing antiferromagnets with opposite local magnetization directions or thicker local free layers on both sides of the free layer.

[0007] The first aspect of the present disclosure provides a neuron device based on spin-orbit moment, comprising: an antiferromagnetic pinning layer, a first ferromagnetic layer and a spin-orbit coupling layer sequentially formed on a substrate; wherein the spin-orbit coupling layer is composed of one or more materials selected from Ta, W and Mo; a free layer formed on the spin-orbit coupling layer and moving the magnetic domain wall according to the spin-orbit moment; a tunneling layer formed on the free layer; a left pinning layer and a right pinning layer formed on both sides of the free layer and having opposite magnetization directions; and a reference layer formed on the tunneling layer; wherein the free layer, the tunneling layer and the reference layer constitute a magnetic tunnel junction, which is used to read neuron signals.

[0008] Furthermore, the spin-orbit coupling layer is made of one or more materials selected from the group consisting of Ta, W, and Mo.

[0009] Furthermore, the free layer has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd and CoFe; the first ferromagnetic layer has in-plane magnetic anisotropy and is composed of one or more materials selected from CoFeB, NiFe and Co; the antiferromagnetic pinned layer has perpendicular exchange interaction and is composed of one or more materials selected from IrMn, FeMn, NiMn, CoMn, PtMn, Mn2Au, NiO and MnO.

[0010] Furthermore, the free layer has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd and CoFe; the first ferromagnetic layer has tilted magnetic anisotropy and is composed of one or more materials selected from CoFeB, NiFe, Co, CoFeAl and CoFe; the antiferromagnetic pinned layer has tilted exchange effect and is composed of one or more materials selected from IrMn, FeMn, NiMn, CoMn, PtMn, Mn2Au, NiO and MnO.

[0011] Furthermore, the free layer has inclined magnetic anisotropy and is composed of one or more materials selected from CoFeB, NiFe, Co, CoFeAl and CoFe; the first ferromagnetic layer has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd and CoFe; the antiferromagnetic pinned layer has perpendicular exchange interaction and is composed of one or more materials selected from IrMn, FeMn, NiMn, CoMn, PtMn, Mn2Au, NiO and MnO.

[0012] Furthermore, the device further includes: a second ferromagnetic layer formed between the antiferromagnetic pinning layer and the first ferromagnetic layer.

[0013] Furthermore, the free layer has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd and CoFe; the first ferromagnetic layer has in-plane magnetic anisotropy and is composed of one or more materials selected from CoFeB, NiFe and Co; the antiferromagnetic pinned layer has perpendicular exchange interaction and is composed of one or more materials selected from IrMn, FeMn, NiMn, CoMn, PtMn, Mn2Au, NiO and MnO; the second ferromagnetic layer has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd and CoFe.

[0014] Furthermore, the device further includes: a second ferromagnetic layer and an insulating layer sequentially formed on the substrate, wherein the antiferromagnetic pinning layer is located on the insulating layer.

[0015] Furthermore, the free layer has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd and CoFe; the first ferromagnetic layer has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd and CoFe; the antiferromagnetic pinned layer has perpendicular exchange interaction and is composed of one or more materials selected from IrMn, FeMn, NiMn, CoMn, PtMn, Mn2Au, NiO and MnO; the insulating layer is composed of SiO2; the second ferromagnetic layer has in-plane magnetic anisotropy and is composed of one or more materials selected from CoFeB, NiFe and Co.

[0016] Furthermore, the device further includes: a second ferromagnetic layer and a spacer layer sequentially formed on the antiferromagnetic pinning layer, wherein the first ferromagnetic layer is located on the spacer layer.

[0017] Furthermore, the free layer has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd and CoFe; the first ferromagnetic layer has in-plane magnetic anisotropy and is composed of one or more materials selected from CoFeB, NiFe and Co; the spacer layer is composed of one or more materials selected from Ru, Ta, W, V, Cr, Rh, Nd, Mo and Re; the second ferromagnetic layer has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd and CoFe; the antiferromagnetic pinned layer has perpendicular exchange interaction and is composed of one or more materials selected from IrMn, FeMn, NiMn, CoMn, PtMn, Mn2Au, NiO and MnO.

[0018] Furthermore, the spin-orbit coupling layer is used to realize the accumulation and leakage characteristics of neurons. When current is passed through the spin-orbit coupling layer, a spin current in a vertical direction is generated based on the spin Hall effect. Under the action of the spin-orbit torque, the movement of the domain wall is realized, simulating the accumulation characteristics of biological neurons; in the absence of current, the free layer and the first ferromagnetic layer are ferromagnetically or antiferromagnetically coupled through the spin-orbit coupling layer through the RKKY effect, so that the domain wall in the free layer has a movement trend opposite to the current driving direction, realizing the leakage characteristics of biological neurons; when the domain wall movement position in the free layer exceeds the threshold region, the magnetic tunnel junction will switch from the antiparallel state to the parallel state, and an external circuit will be used to output a spike pulse to simulate the discharge characteristics of biological neurons.

[0019] Furthermore, the thickness of the free layer is 0.8-2 nm.

[0020] Furthermore, the RKKY effect is related to the thickness and material of the spin-orbit coupling layer and the magnitude of the modulated injection current density.

[0021] Furthermore, by modulating the DMI antisymmetric effect and damping coefficient of appropriate size and different signs, the rate of the neuronal accumulation process can be regulated.

[0022] Furthermore, the device further includes: a left electrode, a right electrode and a top electrode, wherein the left electrode and the right electrode are respectively arranged on two sides of the spin-orbit coupling layer where no free layer is arranged, and the top electrode is located on the reference layer.

[0023] Furthermore, the thickness of the reference layer is greater than that of the free layer, and the thickness is preferably 0.8 to 2 nm.

[0024] Furthermore, the thickness of the tunneling layer is preferably 0.5 to 4 nm.

[0025] Furthermore, the thickness of the left electrode, the right electrode and the top electrode are all 50-200 nm.

[0026] Furthermore, the tilted magnetization direction or tilted magnetic anisotropy of the first ferromagnetic layer or the free layer is used to generate an equivalent field in the x-direction on the free layer, so as to achieve the unchanged chirality of the magnetic domain wall, realize the high-speed movement of the domain wall and avoid the uncertainty of the movement direction of the next accumulation process caused by the change of domain wall chirality induced by precession during the leakage process.

[0027] The second aspect of the present disclosure provides a method for preparing a neuron device based on spin-orbit moment, comprising: sequentially growing an antiferromagnetic pinning layer, a first ferromagnetic layer, a spin-orbit coupling layer, and a free layer on a substrate; forming a left electrode and a right electrode on both sides of the spin-orbit coupling layer; and sequentially forming a tunneling layer, a reference layer, and a top electrode on the free layer, wherein the free layer, the tunneling layer, and the reference layer constitute a magnetic tunnel junction, which is used to read neuron signals.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] (1) The neuron device based on magnetic tunnel junction can accumulate current pulses from synapses under full electric field conditions, and has both high energy efficiency and high reliability self-leakage function. When the accumulated current pulse drives the magnetic domain wall to move and exceeds the threshold area, the neuron will be activated and emit a spike signal, simulating the function of human brain neurons.

[0030] (2) A neuron device with spin-orbit torque-driven magnetic domain wall was realized.

[0031] (3) By modulating the tilted magnetization direction or tilted magnetic anisotropy of the first ferromagnetic layer or the free layer, the chirality of the magnetic domain wall is ensured to remain unchanged, thereby realizing a high-speed neuron device. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] For a more complete understanding of the present disclosure and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, in which:

[0033] Figure 1 Schematically showing a front view of a neuron device based on spin-orbit moment according to the first to third embodiments of the present disclosure;

[0034] Figure 2 Schematically shows a front view of a neuron device based on spin-orbit moment according to a fourth embodiment of the present disclosure;

[0035] Figure 3 Schematically shows a front view of a neuron device based on spin-orbit moment according to a fifth embodiment of the present disclosure;

[0036] Figure 4 Schematically shows a front view of a neuron device based on spin-orbit moment according to a sixth embodiment of the present disclosure;

[0037] Figure 5 Schematically illustrates the leakage-accumulation-discharge characteristics of a neuron device based on spin-orbit moment according to an embodiment of the present disclosure;

[0038] Figure 6 A schematic diagram schematically illustrates the accumulation characteristics of a neuron device based on spin-orbit moment and DM antisymmetric exchange according to an embodiment of the present disclosure;

[0039] Figure 7 A schematic diagram showing the relationship between the accumulation characteristics and the damping coefficient of a neuron device based on spin-orbit moment according to an embodiment of the present disclosure is shown;

[0040] Figure 8The flowchart of the method for preparing a neuron device based on spin-orbit moment according to an embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0041] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0042] It should be understood that when an element (such as a layer, film, region, or substrate) is described as being "on" another element, the element may be directly on the other element or intervening elements may be present. Moreover, in the specification and claims, when it is described that an element is "connected to" another element, the element may be "directly connected to" the other element or "connected to" the other element through a third element.

[0043] The present disclosure provides a neuron device based on spin-orbit moment, comprising: an antiferromagnetic pinning layer, a first ferromagnetic layer, and a spin-orbit coupling layer sequentially formed on a substrate; a free layer formed on the spin-orbit coupling layer and capable of moving magnetic domain walls according to the spin-orbit moment; a tunneling layer formed on the free layer; a left pinning layer and a right pinning layer formed on both sides of the free layer and having opposite magnetization directions; and a reference layer formed on the tunneling layer; wherein the free layer, the tunneling layer, and the reference layer constitute a magnetic tunnel junction, which is used to read neuron signals.

[0044] The spin-orbit moment-based neuron device provided by the embodiments of the present disclosure achieves the following technical effects: First, by depositing antiferromagnets with opposite magnetization directions on both sides of the free layer or retaining / depositing a thicker local free layer, domain wall pinning is achieved. Second, by multiplexing the spin-orbit coupling layer, the accumulation and leakage characteristics of neurons are achieved. On the one hand, when current is passed through the spin-orbit coupling layer, a spin current in a vertical direction is generated due to the spin Hall effect. Under the action of the spin-orbit moment, the movement of the domain wall is achieved, simulating the accumulation characteristics of neurons; on the other hand, in the absence of current, the free layer and the second ferromagnetic layer are coupled ferromagnetically or antiferromagnetically through the spin-orbit coupling layer through the RKKY effect, so that the domain wall in the free layer has a movement trend opposite to the current driving direction, achieving the leakage function. Third, by depositing the stray field of an in-plane magnetically anisotropic ferromagnetic layer or by using exchange bias, interlayer exchange coupling, or annealing in a tilted magnetic field, a tilted magnetization direction or tilted magnetic anisotropy is achieved in the second ferromagnetic layer or free layer. This generates an equivalent field in the x-direction on the free layer, ensuring that the chirality of the domain wall remains unchanged. This allows for high-speed motion of the domain wall while avoiding precession-induced chirality changes during the leakage process, which can lead to uncertainty in the direction of motion during the next accumulation process. Finally, the amplitude, pulse width, and number of current pulses from the synapse drive the motion of the domain wall, achieving the neuronal accumulation function. In the absence of current pulses, the domain wall moves in the opposite direction under the influence of the RKKY of the underlying ferromagnetic layer, achieving the neuronal leakage function. When the domain wall reaches the threshold region, i.e., when the magnetization direction of the corresponding local free layer below the reference layer reverses, the MTJ, in conjunction with peripheral circuits, outputs a spike signal, achieving the neuronal discharge function.

[0045] The technical solution of the present disclosure will be described in detail below in conjunction with the neuron device structure in some specific embodiments of the present disclosure. It should be understood that Figures 1 to 6 The material layers, shapes and structures of various parts of the spin-orbit moment-based neuron device shown in the figure are merely exemplary to help those skilled in the art understand the technical solutions of the present disclosure, and are not intended to limit the scope of protection of the present disclosure.

[0046] Example 1

[0047] Figure 1 The main view of a neuron device based on spin-orbit torque according to the first embodiment of the present disclosure is schematically shown. The device is a neuromorphic device that uses spin-orbit torque to cause magnetic domain wall movement to simulate leakage-accumulation-discharge characteristics similar to those of biological neurons.

[0048] like Figure 1As shown, the spin-orbit torque-based neuron device of the embodiment of the present disclosure includes: a substrate 115, an antiferromagnetic pinned layer 111, a first ferromagnetic layer 110, a spin-orbit coupling layer 109, a right electrode 108, a free layer 107, a right pinned layer 106, a top electrode 105, a reference layer 104, a tunneling layer 103, a left pinned layer 102 and a left electrode 101.

[0049] The substrate 115 may be a sapphire substrate, a silicon substrate, or a quartz substrate with different crystal planes.

[0050] The antiferromagnetic pinning layer 111 is formed on the upper surface of the substrate 115 .

[0051] The first ferromagnetic layer 110 is formed on the upper surface of the antiferromagnetic pinning layer 111 .

[0052] The spin-orbit coupling layer 109 is formed on the upper surface of the first ferromagnetic layer 110. The lateral length of the spin-orbit coupling layer 109 is greater than that of the first ferromagnetic layer 110. In the embodiment of the present disclosure, a left electrode 101 and a right electrode 108 are provided on both sides of the upper surface of the spin-orbit coupling layer 109 where the free layer 107 is not provided.

[0053] The free layer 107 is formed on the upper surface of the spin-orbit coupling layer 109, and the lateral length of the free layer 107 is smaller than that of the spin-orbit coupling layer 109. In the embodiment of the present disclosure, the left electrode 101 and the right electrode 108 are provided on both sides of the upper surface of the spin-orbit coupling layer 109 where the free layer 107 is not provided.

[0054] The tunneling layer 103 is formed on the upper surface of the free layer 107. The lateral length of the tunneling layer 103 is smaller than that of the free layer 107. The region of the free layer 107 facing the tunneling layer 103 forms a threshold region. In the embodiment of the present disclosure, a left pinned layer 102 and a right pinned layer 106 having opposite magnetization directions are disposed on both sides of the upper surface of the free layer 107 where the tunneling layer 103 is not disposed.

[0055] The reference layer 104 is formed on the upper surface of the tunneling layer 103 .

[0056] The top electrode 105 is formed on the upper surface of the reference layer 104 .

[0057] Specifically, the free layer 107, the tunneling layer 103 and the reference layer 104 constitute a magnetic tunnel junction (MTJ) for reading. The free layer 107, the spin-orbit coupling layer 109 and the first ferromagnetic layer 110 are coupled through the RKKY exchange interaction of the spin-orbit coupling layer 109. Specifically, according to the change in the thickness of the spin-orbit coupling layer 109, ferromagnetic coupling or antiferromagnetic coupling can be achieved. Usually, the ferromagnetic and antiferromagnetic couplings show oscillatory changes as the thickness of the spin-orbit coupling layer 109 increases, and the oscillation period is about 1 nm. For example, when the thickness of the spin-orbit coupling layer 109 composed of W material is less than 0.43 nm, ferromagnetic coupling is achieved; when the thickness of the spin-orbit coupling layer 109 composed of W material is greater than 0.43 nm and less than 0.75 nm, antiferromagnetic coupling is achieved.

[0058] In this embodiment, taking antiferromagnetic coupling as an example, the reference layer 104 and the free layer 107 have perpendicular magnetic anisotropy and are composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd, and CoFe. The reference layer 104 preferably has a thickness of 0.8 to 2 nm, and the free layer 107 preferably has a thickness of 0.8 to 2 nm. The tunneling layer 103 is composed of MgO, Al2O3, etc., and preferably has a thickness of 0.5 to 4 nm. The first ferromagnetic layer 110 has a relatively thick in-plane magnetic anisotropy and is composed of one or more materials selected from CoFeB, NiFe, and Co, and its thickness satisfies the in-plane anisotropy. The spin-orbit coupling layer 109 is composed of one or more metals such as Ta, W, and Mo, and is characterized by enabling RKKY exchange interaction between the ferromagnetic layers on both sides, while also exhibiting strong spin-orbit coupling and a significant spin Hall effect. The left and right pinning layers 102 and 106 can be made of antiferromagnetic materials such as IrMn and PtMn, or the same material as the free layer 107. The antiferromagnetic pinning layer 111 exhibits a perpendicular antiferromagnetic exchange interaction and is composed of one or more of IrMn, FeMn, NiMn, CoMn, PtMn, Mn2Au, NiO, and MnO. The left electrode 101, top electrode 105, and right electrode 108 are made of metals or alloys such as Ti, Au, Ti / Au, Ti / Pt, Cr / Au, and Ta / CuN. Each electrode layer preferably has a thickness of 50 to 200 nm.

[0059] In this embodiment, the reference layer 104 is magnetized in the -z direction; the left pinning layer 102 is magnetized in the -z direction, and the right pinning layer 106 is magnetized in the +z direction, allowing the magnetic domain wall to move within the range between the left and right pinning regions without annihilation. The first ferromagnetic layer 110 is magnetized in the x direction, and the bottom antiferromagnetic pinning layer 111 is magnetized in the +z direction, so that the magnetization direction of the first ferromagnetic layer 110 can be pinned in the -z and x directions. A strong exchange bias field exists at the interface between the first ferromagnetic layer 100 and the bottom antiferromagnetic pinning layer 111, which is in perpendicular exchange, causing the magnetization direction of the first ferromagnetic layer 110 to tilt (in the xz plane). Through the RKKY effect of the spacer layer, equivalent fields in the +z and x directions can be generated on the free layer 107, which can maintain the chirality of the domain wall in the free layer 107 unchanged, thereby achieving high-speed motion of the domain wall and avoiding the uncertainty of the motion direction in the next accumulation process caused by the change in domain wall chirality induced by precession during the leakage process.

[0060] Example 2

[0061] The structure of the neuron device based on spin-orbit moment in this embodiment is as follows: Figure 1 As shown, the difference between this embodiment and embodiment 1 is:

[0062] In this embodiment, taking the antiferromagnetic coupling effect as an example, the first ferromagnetic layer 110 has a tilted magnetic anisotropy (in the xz plane) and is composed of one or more materials selected from CoFeB, NiFe, Co, CoFeAl, and CoFe. This can be achieved by annealing in a tilted magnetic field, sputtering at an angle, or the like. The antiferromagnetic pinning layer 111 has a tilted antiferromagnetic exchange effect and is composed of one or more materials selected from IrMn, FeMn, NiMn, CoMn, PtMn, Mn2Au, NiO, and MnO. It should be noted that in this embodiment, the other material layers remain consistent with those in Example 1 and are not further described here.

[0063] Specifically, the reference layer 104 is magnetized in the -z direction, the left pinned layer 102 is magnetized in the -z direction, and the right pinned layer 106 is magnetized in the +z direction, so that the magnetic domain wall can move within the range sandwiched by the left and right pinned regions without annihilation; the bottom antiferromagnetic pinned layer 111 is magnetized in the +z and x directions, so that the magnetization direction of the first ferromagnetic layer 110 can be pinned in the -z and x directions. The magnetization direction of the first ferromagnetic layer 110 with tilted magnetic anisotropy is tilted (in the xz plane). Through the RKKY effect of the spacer layer, equivalent fields in the +z and x directions can be generated on the free layer 107, which can keep the chirality of the domain wall in the free layer 107 unchanged, thereby achieving high-speed movement of the domain wall and avoiding the uncertainty of the movement direction of the next accumulation process caused by the change in chirality of the domain wall induced by precession during the leakage process.

[0064] Example 3

[0065] The structure of the neuron device based on spin-orbit moment in this embodiment is as follows: Figure 1 As shown, the difference between this embodiment and embodiment 1 is:

[0066] In this embodiment, taking antiferromagnetic coupling as an example, the free layer 107 has tilted magnetic anisotropy (in the xz plane) and is composed of one or more materials selected from CoFeB, NiFe, Co, CoFeAl, and CoFe. This can be achieved by annealing in an inclined magnetic field. The first ferromagnetic layer 110 has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd, and CoFe.

[0067] Specifically, the magnetization direction of the left pinned layer 102 is along the -z direction, and the magnetization direction of the right pinned layer 106 is along the +z direction, so that the magnetic domain wall can move in the range sandwiched by the left and right pinned areas without annihilation; the magnetization direction of the first ferromagnetic layer 110 is along the x direction, and the bottom antiferromagnetic pinned layer 111 is along the +z direction, so that the magnetization direction of the first ferromagnetic layer 110 can be pinned in the -z direction, and the magnetization direction of the reference layer 104 is along the -z direction; the magnetization direction of the area where the domain wall can move freely in the ferromagnetic free layer 107 is along the x and +z directions, which can keep the chirality of the domain wall in the free layer 107 unchanged, thereby achieving high-speed movement of the domain wall and avoiding the uncertainty of the movement direction of the next accumulation process caused by the change of domain wall chirality induced by precession during the leakage process.

[0068] Example 4

[0069] Figure 2 Schematically shows a front view of a neuron device based on spin-orbit torque according to a fourth embodiment of the present disclosure.

[0070] like Figure 2 As shown, the spin-orbit moment-based neuron device structure in this embodiment differs from that in embodiment 1 in that:

[0071] In this embodiment, a second ferromagnetic layer 113 is formed between the antiferromagnetic pinning layer 111 and the first ferromagnetic layer 110. The second ferromagnetic layer 113 has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd, and CoFe. The first ferromagnetic layer 110 has oriented magnetic anisotropy and is composed of one or more materials selected from Co, CoFeB, and NiFe.

[0072] In this embodiment, the left pinning layer 102 is magnetized in the -z direction, and the right pinning layer 106 is magnetized in the +z direction, allowing the magnetic domain wall to move within the range between the left and right pinning regions without annihilation. The first ferromagnetic layer 110 is magnetized in the x direction, and the bottom antiferromagnetic pinning layer 111 is magnetized in the +z direction, so that the magnetization direction of the second ferromagnetic layer 113 can be pinned in the -z direction, and the reference layer 104 is magnetized in the -z direction. The exchange bias field at the interface between the first ferromagnetic layer 110 and the second ferromagnetic layer 113 can cause the magnetization direction of the first ferromagnetic layer 110 to tilt (in the xz plane). Through the RKKY effect of the spacer layer, equivalent fields in the +z and x directions can be generated on the free layer 107. This maintains the chirality of the domain wall in the free layer 107 unchanged, enabling high-speed motion of the domain wall while avoiding the uncertainty of the motion direction in the next accumulation process caused by precession-induced chirality changes in the domain wall during the leakage process.

[0073] Example 5

[0074] Figure 3 Schematically shows a front view of a neuron device based on spin-orbit torque according to a fifth embodiment of the present disclosure.

[0075] like Figure 3 As shown, the spin-orbit moment-based neuron device structure in this embodiment differs from that in embodiment 1 in that:

[0076] A second ferromagnetic layer 113 and an insulating layer 112 are sequentially formed on the substrate, wherein an antiferromagnetic pinning layer 111 is located on the insulating layer 112. The first ferromagnetic layer 110 has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd, and CoFe. The second ferromagnetic layer 113 has in-plane magnetic anisotropy and is composed of one or more materials selected from CoFeB, NiFe, and Co. The insulating layer 112 is composed of an insulating material such as SiO2.

[0077] In this embodiment, the magnetization direction of the left pinning layer 102 is along the -z direction, and the magnetization direction of the right pinning layer 106 is along the +z direction, so that the magnetic domain wall can move within the range sandwiched by the left and right pinning regions without annihilation; the bottom antiferromagnetic pinning layer 111 is along the +z direction, so that the magnetization direction of the first ferromagnetic layer 110 can be pinned in the -z direction, and the magnetization direction of the reference layer 104 is along the -z direction; the magnetization direction of the second ferromagnetic layer 113 is along the x direction, and the stray field generated by the second ferromagnetic layer 113 can keep the chirality of the domain wall in the free layer 107 unchanged, thereby achieving high-speed movement of the domain wall and avoiding the uncertainty of the movement direction in the next accumulation process caused by the change of domain wall chirality induced by precession during the leakage process.

[0078] Example 6

[0079] Figure 4 Schematically shows a front view of a neuron device based on spin-orbit torque according to a sixth embodiment of the present disclosure.

[0080] like Figure 4 As shown, the spin-orbit moment-based neuron device structure in this embodiment differs from that in embodiment 1 in that:

[0081] A second ferromagnetic layer 113 and a spacer layer 114 are sequentially formed on the antiferromagnetic pinning layer 111, with the first ferromagnetic layer 110 located on the spacer layer 114. The spacer layer 114 is composed of one or more materials selected from Ru, Ta, W, V, Cr, Rh, Nd, Mo, and Re. The second ferromagnetic layer 113 exhibits perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd, and CoFe.

[0082] In this embodiment, the left pinning layer 102 is magnetized in the −z direction, and the right pinning layer 106 is magnetized in the +z direction, allowing the magnetic domain wall to move within the range between the left and right pinning regions without annihilation. The first ferromagnetic layer 110 is magnetized in the x direction, and the bottom antiferromagnetic pinning layer 111 is magnetized in the +z direction, so that the magnetization direction of the second ferromagnetic layer 113 can be pinned in the −z direction, and the reference layer is magnetized in the −z direction. The first ferromagnetic layer 110 and the second ferromagnetic layer 113 are coupled via the RKKY exchange interaction of the spin-orbit coupling layer 109, causing the magnetization direction of the first ferromagnetic layer 110 to tilt (in the xz plane). The RKKY interaction of the spin-orbit coupling layer 109 generates equivalent fields in the +z and x directions on the free layer 107, which maintains the chirality of the domain wall in the free layer 107 unchanged. This allows for high-speed motion of the domain wall while avoiding precession-induced chirality changes in the domain wall during leakage, which could lead to uncertainty in the direction of motion in the next accumulation process.

[0083] In Examples 1 to 6 provided herein, in the initial state, the z-direction magnetization component of the region where the domain wall can freely move in the ferromagnetic free layer is along the +z direction, that is, the magnetic domain wall is located near the boundary of the left pinned layer region. Therefore, when current is injected between the left and right electrodes, the current flows through the spin-orbit coupling layer, generating a perpendicular spin current under the action of the spin Hall effect. The generated spin-orbit torque drives the domain wall to move in the +x direction, simulating the accumulation process of neurons. When no current is injected, the first ferromagnetic layer indirectly acts on the ferromagnetic free layer through the intermediate synthetic antiferromagnetic coupling layer, causing its z-direction magnetization component to tend to the +z direction, even if the domain wall moves in the -x direction, simulating the leakage process of neurons; after a series of accumulation and leakage processes, the domain wall movement exceeds the corresponding region of the ferromagnetic reference layer. At this time, the magnetization direction of the free layer flips from the +z direction to the -z direction, and the tunneling magnetoresistance changes from a larger antiparallel state resistance to a smaller parallel state resistance. Combined with an external circuit, a spike pulse can be output, simulating the discharge process of neurons.

[0084] Figure 5 Schematic diagram showing the leakage-accumulation-discharge characteristics of a spin-orbit moment-based neuron device according to an embodiment of the present disclosure, wherein the free layer size is 60×300 nm 2 The left and right pinning regions are 60×30nm in size. 2 . Six pulses with an amplitude of 4×10 7 A / cm 2 , the current pulse has a pulse width of 0.4ns and a period of 0.8ns. When the amplitude of the current pulse is 4×10 7 A / cm 2 During this period, the magnetic domain wall moves along the +x direction and continues to accumulate; when the current pulse amplitude is 0, the magnetic domain wall moves along the -x direction under the action of RKKY exchange, realizing the leakage process; after 6 consecutive pulses, the magnetic domain wall reaches the threshold area and the neuron is activated. At this time, the output circuit will output a spike signal; then, the neuron enters the withdrawal process, and under the action of RKKY antiferromagnetic coupling, the magnetic domain wall moves along the -x direction to the initial position, realizing the complete leakage-accumulation-discharge process of biological neurons.

[0085] Figure 6 The schematic diagram shows the accumulation characteristics of the neuron device based on spin-orbit moment and the DM antisymmetric exchange according to an embodiment of the present disclosure, Figure 6 It can be seen that as the DMI antisymmetric effect increases, the speed of magnetic domain wall movement accelerates. Therefore, the characteristics of the accumulation process can be appropriately adjusted by adjusting the strength of the DMI antisymmetric effect as needed.

[0086] Figure 7The figure schematically shows the relationship between the accumulation characteristics and the damping coefficient of the neuron device based on the spin-orbit moment according to an embodiment of the present disclosure, wherein Figure 7 It can be seen that as the damping coefficient increases, the movement speed of the magnetic domain wall slows down. Therefore, the characteristics of the accumulation process can be appropriately adjusted by adjusting the damping coefficient as needed.

[0087] It should be noted that the length, width, and specific material examples of each semiconductor material layer in the above embodiments are merely illustrative and do not constitute limitations of the embodiments of the present disclosure.

[0088] Figure 8 The flowchart of the method for preparing a neuron device based on spin-orbit moment according to an embodiment of the present disclosure is schematically shown. The structure of the neuron device prepared by the method steps is as follows: Figures 1 to 4 shown.

[0089] like Figure 8 As shown, the method for preparing the spin-orbit moment-based neuron device includes:

[0090] S801 , sequentially growing an antiferromagnetic pinned layer, a first ferromagnetic layer, a spin-orbit coupling layer, and a free layer on a substrate.

[0091] S802 , forming a left electrode and a right electrode on both sides of the spin-orbit coupling layer respectively.

[0092] S803 , sequentially forming a tunneling layer, a reference layer, and a top electrode on the free layer, wherein the free layer, the tunneling layer, and the reference layer constitute a magnetic tunnel junction, and the magnetic tunnel junction is used to read neuron signals.

[0093] It should be noted that the structure of the neuron device prepared by the above-mentioned process in the embodiment of the present disclosure is as follows: Figures 1 to 4 As shown, the specific material layers, layer thicknesses, and structures of the material layers are also as shown. Figures 1 to 4 As shown, no further details are given here.

[0094] It should be noted that the process methods and materials used in the above steps in the embodiments of the present disclosure are only exemplary descriptions. For example, the above semiconductor layer can use conventional thin film growth and etching methods such as PVD, MBE, ALD, IBE, RIE, ICP and other methods to obtain high-quality epitaxial thin films, etc., and the present disclosure does not limit this.

[0095] From the above description, it can be seen that the above embodiments of the present disclosure achieve at least the following technical effects:

[0096] 1) This neuron device based on a magnetic tunnel junction can accumulate current pulses from synapses under full electric field conditions, and has both high energy efficiency and highly reliable self-leakage functions. When the accumulated current pulse drives the movement of the magnetic domain wall and exceeds the threshold area, the neuron will be activated and emit a spike signal, simulating the function of neurons in the human brain.

[0097] 2) A neuron device with spin-orbit torque-driven magnetic domain wall was realized.

[0098] 3) By modulating the tilted magnetization direction or tilted magnetic anisotropy of the first ferromagnetic layer or the free layer, the chirality of the magnetic domain wall is ensured to remain unchanged, thereby realizing a high-speed neuron device.

[0099] While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive.

[0100] Those skilled in the art will appreciate that the features described in the various embodiments and / or claims of this disclosure may be combined and / or coupled in a variety of ways, even if such combinations or couplings are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure may be combined and / or coupled in a variety of ways without departing from the spirit and teachings of this disclosure. All such combinations and / or couplings are intended to fall within the scope of this disclosure.

[0101] Although the present disclosure has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made to the present disclosure without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents. Therefore, the scope of the present disclosure should not be limited to the above-described embodiments, but should be determined not only by the appended claims but also by the equivalents of the appended claims.

Claims

1. A neuron device based on spin-orbit moment, characterized in that: include: An antiferromagnetic pinning layer (111), a first ferromagnetic layer (110), and a spin-orbit coupling layer (109) are sequentially formed on a substrate; A free layer (107) formed on the spin-orbit coupling layer (109) and causing the magnetic domain wall to move according to the spin-orbit moment; a tunneling layer (103) formed on the free layer (107); A left pinning layer (102) and a right pinning layer (106) formed on both sides of the free layer (107) and having opposite magnetization directions; A reference layer (104) is formed on the tunneling layer (103); wherein the free layer (107), the tunneling layer (103) and the reference layer (104) constitute a magnetic tunnel junction, and the magnetic tunnel junction is used to read neuron signals; The spin-orbit coupling layer (109) is composed of one or more materials selected from the group consisting of Ta, W, and Mo; a second ferromagnetic layer (113) formed between the antiferromagnetic pinning layer (111) and the first ferromagnetic layer (110); A left electrode (101) and a right electrode (108) are provided on both sides of the upper surface of the spin-orbit coupling layer (109) where the free layer (107) is not provided; The spin-orbit coupling layer (109) is used to realize the accumulation and leakage characteristics of neurons; When current is passed through the spin-orbit coupling layer (109), a spin current in a vertical direction is generated based on the spin Hall effect, and under the action of the spin-orbit moment, the movement of the domain wall is realized, simulating the accumulation characteristics of biological neurons; when there is no current in the spin-orbit coupling layer (109), the free layer (107) and the first ferromagnetic layer (110) are coupled ferromagnetically or antiferromagnetically through the RKKY action of the spin-orbit coupling layer (109), so that the domain wall in the free layer (107) has a movement trend opposite to the current driving direction, realizing the leakage characteristics of biological neurons.

2. The spin-orbit moment-based neuron device according to claim 1, characterized in that: The free layer (107) has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd and CoFe; The first ferromagnetic layer (110) has in-plane magnetic anisotropy and is composed of one or more materials selected from CoFeB, NiFe and Co; The antiferromagnetic pinning layer (111) has a vertical exchange effect and is composed of one or more materials selected from the group consisting of IrMn, FeMn, NiMn, CoMn, PtMn, Mn2Au, NiO and MnO.

3. The spin-orbit moment-based neuron device according to claim 1, characterized in that: The free layer (107) has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd and CoFe; The first ferromagnetic layer (110) has tilted magnetic anisotropy and is composed of one or more materials selected from CoFeB, NiFe, Co, CoFeAl, and CoFe; The antiferromagnetic pinning layer (111) has a tilted exchange effect and is composed of one or more materials selected from the group consisting of IrMn, FeMn, NiMn, CoMn, PtMn, Mn2Au, NiO and MnO.

4. The spin-orbit moment-based neuron device according to claim 1, characterized in that: The free layer (107) has tilted magnetic anisotropy and is composed of one or more materials selected from CoFeB, NiFe, Co, CoFeAl and CoFe; The first ferromagnetic layer (110) has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd and CoFe; The antiferromagnetic pinning layer (111) has a vertical exchange effect and is composed of one or more materials selected from the group consisting of IrMn, FeMn, NiMn, CoMn, PtMn, Mn2Au, NiO and MnO.

5. The spin-orbit moment-based neuron device according to claim 1, characterized in that: The free layer (107) has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd and CoFe; The first ferromagnetic layer (110) has in-plane magnetic anisotropy and is composed of one or more materials selected from CoFeB, NiFe and Co; The antiferromagnetic pinning layer (111) has a vertical exchange effect and is composed of one or more materials selected from the group consisting of IrMn, FeMn, NiMn, CoMn, PtMn, Mn2Au, NiO and MnO; The second ferromagnetic layer (113) has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd and CoFe.

6. The spin-orbit moment-based neuron device according to claim 1, characterized in that: Also includes: A second ferromagnetic layer (113) and an insulating layer (112) are sequentially formed on the substrate, wherein the antiferromagnetic pinning layer (111) is located on the insulating layer (112).

7. The spin-orbit moment-based neuron device according to claim 6, characterized in that: The free layer (107) has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd and CoFe; The first ferromagnetic layer (110) has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd and CoFe; The antiferromagnetic pinning layer (111) has a vertical exchange effect and is composed of one or more materials selected from the group consisting of IrMn, FeMn, NiMn, CoMn, PtMn, Mn2Au, NiO and MnO; The insulating layer (112) is composed of SiO2; The second ferromagnetic layer (113) has in-plane magnetic anisotropy and is composed of one or more materials selected from CoFeB, NiFe and Co.

8. The spin-orbit moment-based neuron device according to claim 1, characterized in that: Also includes: A second ferromagnetic layer (113) and a spacer layer (114) are sequentially formed on the antiferromagnetic pinning layer (111), wherein the first ferromagnetic layer (110) is located on the spacer layer (114).

9. The spin-orbit moment-based neuron device according to claim 8, characterized in that: The free layer (107) has perpendicular magnetic anisotropy and is composed of one or more materials selected from CoFeB, Co / Pt, CoFeAl, Co / Pd and CoFe; The first ferromagnetic layer (110) has in-plane magnetic anisotropy and is composed of one or more materials selected from CoFeB, NiFe and Co; The spacer layer (114) is composed of one or more materials selected from the group consisting of Ru, Ta, W, V, Cr, Rh, Nd, Mo, and Re; The second ferromagnetic layer (113) has perpendicular magnetic anisotropy and is composed of one or more materials selected from the group consisting of CoFeB, Co / Pt, CoFeAl, Co / Pd, and CoFe; The antiferromagnetic pinning layer (111) has a vertical exchange effect and is composed of one or more materials selected from the group consisting of IrMn, FeMn, NiMn, CoMn, PtMn, Mn2Au, NiO and MnO.

10. The spin-orbit moment-based neuron device according to claim 1, characterized in that: The thickness of the free layer (107) is 0.8 nm to 2 nm.

11. The spin-orbit moment-based neuron device according to claim 1, characterized in that: The neuron device further includes: A left electrode (101), a right electrode (108) and a top electrode (105); wherein, The left electrode (101) and the right electrode (108) are respectively arranged on two sides of the spin-orbit coupling layer (109) where the free layer (107) is not arranged, and the top electrode (105) is located on the reference layer (104).

12. The spin-orbit moment-based neuron device according to claim 1, characterized in that: The thickness of the reference layer (104) is greater than the thickness of the free layer (107).

13. The spin-orbit moment-based neuron device according to claim 1, characterized in that: The reference layer (104) has a thickness of 0.8 nm to 2 nm.

14. The spin-orbit moment-based neuron device according to claim 1, characterized in that: The tunneling layer (103) has a thickness of 0.5 nm to 4 nm.

15. The spin-orbit moment-based neuron device according to claim 11, characterized in that: The thickness of the left electrode (101), the right electrode (108) and the top electrode (105) are all 50nm to 200nm.

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