Magnetic memory and writing method
By introducing two magnetic layers with antiferromagnetic coupling and the elliptical MTJ design in SOT-MRAM, the write error problem caused by excessive SOT current is solved, and the stability and storage density of the memory are improved.
Patent Information
- Application Number
- CN202311681697.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-06
- Publication Date
- 2025-06-06
AI Technical Summary
Due to the large write current required for the SOT-MRAM cell circuit, the size of the driving transistor is larger, resulting in large dynamic power consumption and low storage density. When the SOT current is too large, it may lead to erroneous writes of the unselected MTJ.
A free layer including two magnetic layers is adopted. The magnetization direction of the two magnetic layers is antiferromagnetic coupling, and the magnetization direction cannot be reversed by the SOT torque alone, thereby preventing miswrites. In addition, the MTJ can be set to an elliptical shape, and the magnetization direction of the free layer is along the long axis of the MTJ, and the magnetization direction of the pinned layer and the long axis of the MTJ are included to ensure that the STT torque can act effectively.
By increasing the interaction force of the magnetic layer, the stability of the magnetic memory is improved, and the write error problem caused by excessive SOT current is avoided. At the same time, the shape and magnetization direction of the MTJ are optimized to ensure effective write operation.
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Figure CN120111894A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of storage, and in particular to a magnetic storage device and a writing method. Background Art
[0002] Spin-orbit torque magnetic memory (SOT-MRAM) has the advantages of ultra-fast writing, unlimited erasing, and non-volatility. Figure 1 As shown in the figure, the unit circuit of SOT-MRAM is usually a 2T1MTJ structure. Due to the large write current required, the size of the driving transistor is large, resulting in high dynamic power consumption and low storage density. In response to this, the industry has proposed a multi-bit SOT-MRAM solution that can realize the (n+2)TnMTJ structure, which is expected to improve storage density.
[0003] like Figure 2 As shown in the figure, the multi-bit SOT-MRAM structure is: N magnetic tunnel junctions (MTJs) are placed on the heavy metal layer, each MTJ includes a free layer, an insulating layer, and a pinned layer, two transistors are connected at both ends of the heavy metal layer, and one end of each MTJ is connected to a transistor, thereby achieving (n+2)TnMTJ storage density. The write operation is: applying a spin orbit torque (SOT) current in the strong spin-orbit coupling layer (generating SOT torque), and applying a spin transfer torque (STT) current in the selected MTJ to be written (generating STT torque), and completing data writing (flipping the magnetization direction of the free layer) under the cooperation of the SOT torque and the STT torque.
[0004] However, the STT current will also flow into the strong spin-orbit coupling layer, and after superposition with the SOT current, the SOT current will be too large, for example Figure 2 The area below the leftmost MTJ in . Figure 3 As shown, when the SOT current is too large, the magnetization direction of the free layer may be pulled by the SOT torque generated by it, causing the magnetization direction to be flipped, resulting in miswriting of the unselected MTJ. Summary of the invention
[0005] The present application provides a magnetic memory and a writing method for avoiding the miswriting problem caused when the SOT current in the strong spin-orbit coupling layer is too large.
[0006] The first aspect of the present application provides a magnetic storage device:
[0007] The magnetic memory comprises a strong spin-orbit coupling layer and a plurality of MTJs placed on the strong spin-orbit coupling layer. Each of the plurality of MTJs comprises a free layer, an insulating layer and a pinning layer. The free layer comprises a first magnetic layer, a second magnetic layer and a spacer layer.
[0008] In the above scheme, since the free layer includes two magnetic layers, there is an interaction force between the magnetization directions of the two magnetic layers, which can improve stability. Therefore, the magnetization directions of the two magnetic layers cannot be reversed by the SOT torque alone, thereby preventing miswriting.
[0009] In a possible implementation manner, the first magnetic layer and the second magnetic layer form an antiferromagnetic coupling.
[0010] In the above scheme, antiferromagnetic coupling means that the magnetization directions of the first magnetic layer and the second magnetic layer are antiparallel, so there is a very strong interaction force between the two magnetization directions, which further improves the effectiveness of preventing miswriting.
[0011] In a possible implementation, the MTJ is elliptical, and the long axis of the MTJ is parallel to or has an angle other than 90 degrees with the direction of the SOT current applied to the strong spin-orbit coupling layer.
[0012] In the above scheme, the elliptical shape of the MTJ is conducive to setting the magnetization direction of the free layer along the long axis of the ellipse. By setting the long axis of the MTJ to be parallel to the direction of the SOT current or to have an angle other than 90 degrees, the magnetization direction of the free layer is angled with the direction of the SOT torque, thereby avoiding the situation where writing cannot be performed due to the SOT torque being unable to pull the magnetization direction of the free layer.
[0013] In a possible implementation, the magnetization direction of the free layer is along the long axis of the MTJ, and the magnetization direction of the pinned layer is along the long axis of the MTJ, or has an angle with the long axis of the MTJ.
[0014] In the above scheme, the SOT torque and the STT torque can act on the magnetization direction of the first magnetic layer and the second magnetic layer at the same time. In this case, since the direction of the STT torque is opposite to or in the same direction as the magnetization direction of the pinned layer, the magnetization direction of the pinned layer is set to have an angle with the long axis of the MTJ, which can ensure that the STT torque can pull the magnetization direction of the free layer, and then work together with the SOT torque to achieve flipping. Alternatively, the SOT torque mainly acts on the magnetization direction of the bottom magnetic layer, and the STT torque mainly acts on the magnetization direction of the top magnetic layer. In this case, since the SOT torque can pull the magnetization direction of the bottom magnetic layer away from the long axis, the magnetization direction of the top magnetic layer deviates from the long axis as the magnetization direction of the bottom magnetic layer changes. Therefore, the magnetization direction of the pinned layer is along the long axis of the MTJ or has an angle with the long axis of the MTJ, which can make the STT torque pull the magnetization direction of the top magnetic layer, thereby achieving flipping.
[0015] In a possible implementation, the MTJ is circular or square, and the magnetization direction of the free layer and / or the magnetization direction of the pinned layer is at an angle other than 90 degrees to the direction of the STT current flowing perpendicularly through the MTJ.
[0016] In the above scheme, compared with the elliptical shape, the MTJ is set to be circular or square, and there is no need to consider the problem of setting the magnetization direction of the free layer along the long axis, so the volume of the MTJ can be reduced. And setting the magnetization direction of the free layer and the pinned layer to the above form can ensure that the magnetization direction of the free layer has an angle with the SOT and STT torques, thereby achieving flipping.
[0017] In a possible implementation, the material of the strong spin-orbit coupling layer includes one or more of platinum Pt, tungsten W, tantalum Ta, copper Cu, topological insulator, antiferromagnetic IrMn, and antiferromagnetic PtMn.
[0018] In a possible implementation, the material of the first magnetic layer and the second magnetic layer includes one or more of iron Fe, cobalt Co, nickel Ni, CoFe, CoFeB, (Co / Pt)n, (Co / Ni)n and (Co / Pd)n.
[0019] In a possible implementation, the material of the spacer layer includes one or more of ruthenium Ru, niobium Nb, tantalum Ta, chromium Cr, molybdenum Mo, tungsten W, rhenium Re, osmium Os, rhodium Rh, iridium Ir, platinum Pt, copper Cu, silver Ag, and gold Au.
[0020] In the above solution, the material of the spacer layer can ensure that the magnetization directions of the first magnetic layer and the second magnetic layer produce interlayer coupling, thereby avoiding miswriting.
[0021] In a possible implementation, the thickness of the spacer layer is less than 5 nm.
[0022] In the above solution, the thickness of the spacer layer is set to be less than 5 nm, which can effectively achieve antiferromagnetic coupling.
[0023] The second aspect of the present application provides a method for writing into a magnetic memory, wherein the magnetic memory is the magnetic memory in the first aspect, and the sequence of the writing method is:
[0024] Step 1, applying a first current;
[0025] Step 2, applying a second current;
[0026] Step 3, removing the first current;
[0027] Step 4, removing the second current;
[0028] The first current is a SOT current applied to a strong spin-orbit coupling layer of a magnetic memory, and the second current is a STT current applied to an MTJ to be written in the magnetic memory. Alternatively, the second current is a SOT current applied to a strong spin-orbit coupling layer of a magnetic memory, and the first current is a STT current applied to an MTJ to be written in the magnetic memory.
[0029] In the above scheme, applying and removing the corresponding current in sequence according to the above four steps can cause the SOT and STT torques to flip the magnetization direction of the free layer, thereby achieving writing.
[0030] A third aspect of the present application provides an electronic device, which includes the magnetic memory of the first aspect.
[0031] A fourth aspect of the present application provides a chip, which includes the magnetic memory of the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Figure 1 It is a schematic diagram of the structure of an existing magnetic storage device;
[0033] Figure 2 It is a schematic diagram of the superposition of SOT current and STT current;
[0034] Figure 3 Schematic diagram of the magnetization direction of the free layer flipping under the SOT torque;
[0035] Figure 4 It is a schematic diagram of the structure of MTJ in this application;
[0036] Figure 5 A schematic diagram of the structure of the magnetic storage device in this application;
[0037] Figure 6 A schematic diagram of a process for writing a method in this application;
[0038] Figure 7 Another schematic diagram of the writing method in this application;
[0039] Figure 8 A schematic diagram of the reversal of the magnetization direction of the free layer in this application;
[0040] Fig. 9 Another schematic diagram of the reversal of the magnetization direction of the free layer in this application;
[0041] Fig.10 Another schematic diagram of the reversal of the magnetization direction of the free layer in this application;
[0042] Fig.11 Another schematic diagram of the reversal of the magnetization direction of the free layer in this application;
[0043] Fig.12 Another structural schematic diagram of the magnetic storage device in this application;
[0044] Fig.13 Another schematic diagram of the reversal of the magnetization direction of the free layer in this application;
[0045] Fig.14 Another schematic diagram of the reversal of the magnetization direction of the free layer in this application;
[0046] Fig.15 Another schematic diagram of the reversal of the magnetization direction of the free layer in this application;
[0047] Fig.16 Another schematic diagram of the reversal of the magnetization direction of the free layer in this application;
[0048] Fig.17 Another structural schematic diagram of the magnetic storage device in this application;
[0049] Fig.18 Another schematic diagram of the reversal of the magnetization direction of the free layer in this application;
[0050] Fig.19 A schematic diagram showing that the magnetization direction of the free layer in the present application cannot be reversed;
[0051] Fig.20a Another schematic diagram of the reversal of the magnetization direction of the free layer in this application;
[0052] Fig.20b Another schematic diagram of the reversal of the magnetization direction of the free layer in this application;
[0053] Fig.20c Another schematic diagram of the reversal of the magnetization direction of the free layer in this application;
[0054] Fig.21Another structural schematic diagram of the magnetic storage device in this application;
[0055] Fig. 22 Another schematic diagram of the reversal of the magnetization direction of the free layer in this application;
[0056] Fig.23 Another schematic diagram of the reversal of the magnetization direction of the free layer in this application;
[0057] Fig.24 Another structural schematic diagram of the magnetic storage device in this application;
[0058] Fig.25 Another schematic diagram of the reversal of the magnetization direction of the free layer in this application;
[0059] Fig.26 Another schematic diagram of the reversal of the magnetization direction of the free layer in this application. DETAILED DESCRIPTION
[0060] The following describes the embodiments of the present application in conjunction with the accompanying drawings. Obviously, the described embodiments are only embodiments of a part of the present application, rather than all embodiments. It is known to those skilled in the art that with the development of technology and the emergence of new scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.
[0061] The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.
[0062] To facilitate understanding of this application, some concepts involved in this application are introduced below:
[0063] Easy axis: Under the combined effects of magnetocrystalline anisotropy, shape anisotropy, exchange interaction, dipole interaction, etc., the spontaneous magnetization of magnetic materials is always in one or several specific directions, which are called easy magnetization axes or easy axes. When an external field is applied, the magnetization direction can be turned away from the easy axis direction.
[0064] SOT: The current flowing into the heterojunction of ferromagnetic and heavy metals (platinum, tantalum, tungsten, etc.) will cause the accumulation of spin current at the interface of the ferromagnetic layer, thereby generating a spin-orbit torque (SOT) on the magnetic moment in the ferromagnetic layer, causing it to rotate, precess, and flip. The directions of the current, spin current, and SOT torque are perpendicular to each other. The spin-orbit torque is usually believed to come from the spin Hall effect or the Rashba effect, and the root cause is the strong spin-orbit coupling of heavy metal materials.
[0065] STT: When a spin-polarized current passes through a magnetic material, the spin of the polarized electrons in the current transfers angular momentum to the magnetic moment of the magnetic material, which is equivalent to the spin-polarized current generating a torque acting on the magnetic moment of the magnetic material, causing it to rotate, precess, and flip. This phenomenon is called the spin transfer torque (STT) effect. For a sandwich-structured magnetic tunnel junction, it includes a magnetic free layer, an insulating layer, and a magnetic pinned layer (or reference layer, fixed layer), in which the magnetization direction of the pinned layer is fixed, and the magnetization direction of the free layer can change under the action of the spin-polarized current. When electrons flow from the pinned layer to the free layer (current flows from the free layer to the pinned layer), in the pinned layer, electrons whose spin direction is consistent with the magnetization direction of the pinned layer can pass more easily, while electrons with opposite spin directions are scattered by the pinned layer. Therefore, after passing through the pinned layer, the current is polarized along the magnetization direction of the pinned layer; when the spin-polarized electrons pass through the intermediate insulating layer, the electron spin direction can remain unchanged due to the small thickness of the intermediate layer; when the spin-polarized electrons reach the free layer, they will generate an STT torque on the magnetic moment of the free layer, causing the direction of the free layer to turn to the same direction as the spin direction of the polarized electrons, that is, the magnetization direction of the pinned layer, that is, the magnetization directions of the free layer and the pinned layer tend to be arranged in parallel. On the contrary, when electrons flow from the free layer to the pinned layer (current flows from the pinned layer to the free layer), after passing through the free layer, the spin of the electrons is polarized to be consistent with the direction of the magnetic moment of the free layer. After the polarized current passes through the intermediate layer, similar transmission and reflection occur at the interface of the pinned layer. The polarization direction of the electrons reflected back to the free layer through the pinned layer is opposite to the magnetization direction of the pinned layer, causing the direction of the free layer to turn to the direction opposite to the magnetization direction of the pinned layer, that is, the magnetization directions of the free layer and the pinned layer tend to be arranged in anti-parallel.
[0066] The magnetic memory in the present application can be made into a storage chip, or can also be integrated into electronic devices such as processors, mobile phones, computers, servers, etc.
[0067] The magnetic memory of the present application includes a strong spin-orbit coupling layer and a plurality of MTJs placed on the strong spin-orbit coupling layer, such as Figure 4As shown, each MTJ includes a free layer, an insulating layer and a pinned layer, wherein the free layer includes a first magnetic layer, a second magnetic layer and a spacer layer. Optionally, the first magnetic layer and the second magnetic layer form an antiferromagnetic coupling, that is, the magnetization direction of the first magnetic layer is antiparallel to the magnetization direction of the second magnetic layer. This structure is called artificial antiferromagnetism or synthetic antiferromagnetism (SAF). Since the first magnetic layer and the second magnetic layer form an antiferromagnetic coupling, it is very difficult to flip the magnetization direction of the free layer, which cannot be achieved by relying solely on the SOT torque. In other words, even if the SOT current is too large, it will not cause miswriting of the unselected MTJ. The thickness of the spacer layer can be set to less than 5nm, thereby ensuring that the first magnetic layer and the second magnetic layer can form an antiferromagnetic coupling.
[0068] The material of the strong spin-orbit coupling layer can be one or more of heavy metal Pt, heavy metal W, heavy metal Ta, metal Cu, topological insulator, antiferromagnetic IrMn, antiferromagnetic PtMn; the material of the insulating layer can be MgO or Al 2 O 3 ; The material of the first magnetic layer includes one or more of iron Fe, cobalt Co, nickel Ni, CoFe, CoFeB, (Co / Pt)n, (Co / Ni)n, and (Co / Pd)n, and the material of the second magnetic layer is similar to that of the first magnetic layer; the material of the spacer layer includes one or more of ruthenium Ru, niobium Nb, tantalum Ta, chromium Cr, molybdenum Mo, tungsten W, rhenium Re, osmium Os, rhodium Rh, iridium Ir, platinum Pt, copper Cu, silver Ag, and gold Au.
[0069] The above is a relatively general introduction to the magnetic storage in the present application. Now, the magnetic storage in the present application will be introduced in detail:
[0070] The present application can be divided into two different implementations. One is that the SOT torque and the STT torque act on the magnetization direction of the first magnetic layer and the second magnetic layer at the same time; the other is that the SOT torque mainly acts on the magnetization direction of the bottom magnetic layer, and the STT torque mainly acts on the magnetization direction of the top magnetic layer, which are discussed separately below.
[0071] Case 1: The SOT torque and the STT torque act on the magnetization directions of the first magnetic layer and the second magnetic layer simultaneously.
[0072] In this implementation, the easy axis of the magnetization direction of the free layer of the MTJ needs to have an angle with the direction of the SOT torque generated by the SOT current, so as to ensure that the SOT torque can pull the initial magnetization direction of the free layer. Since the direction of the STT torque is in the same direction or antiparallel to the magnetization direction of the pinned layer, the magnetization direction of the pinned layer also needs to have an angle with the above-mentioned easy axis, so as to ensure that the STT torque can pull the initial magnetization direction of the free layer. In addition, the direction of the STT torque also has an angle with the direction of the SOT torque to avoid the two torques from canceling each other out. When the strong spin-orbit coupling layer is applied with a SOT current, and the selected MTJ is applied with an STT current, the selected MTJ can meet the following conditions: the direction of the SOT torque and the direction of the STT torque are respectively toward the two sides of the above-mentioned easy axis, and toward the same side of the vertical line of the midpoint of the above-mentioned easy axis. Through the above-mentioned setting, for the selected MTJ, the SOT torque and the STT torque generated by applying the SOT current and the STT current can effectively flip the magnetization direction of its free layer, thereby achieving writing.
[0073] The following is a detailed example:
[0074] like Figure 5 As shown, the MTJ in the magnetic memory of the present application is elliptical, and the easy axis of the magnetization direction of the free layer is along the long axis of the MTJ; the long axis of the MTJ and the direction of the SOT current flowing through the strong spin-orbit coupling layer have an angle other than 90 degrees, for example, 45 degrees; the magnetization direction of the pinned layer and the long axis of the MTJ have an angle, for example, it can be opposite to the direction of the SOT current, and the magnetization direction of the pinned layer can be achieved by annealing in a magnetic field in a specified direction during the preparation process. Optionally, in order to facilitate production and manufacturing, the magnetization direction of the free layer and the magnetization direction of the pinned layer are both perpendicular to the STT current flowing through the MTJ, that is, parallel to the upper and lower surfaces of the MTJ.
[0075] The complete stack film of the magnetic memory can be W(3.5) / CoFeB(1) / Ru(0.8) / CoFeB(1) / MgO(1) / CoFeB(2) / CoFeB(0.5) / Ru(0.8) / CoFeB(2) / IrMn(7.5), with the thickness in the brackets in nm. W(3.5) is a strong spin-orbit coupling layer; CoFeB(1) / Ru(0.8) / CoFeB(1) are the first magnetic layer, the spacer layer and the second magnetic layer respectively; MgO(1) is an insulating layer; CoFeB(2) / CoFeB(0.5) / Ru(0.8) / CoFeB(2) / IrMn(7.5) is a pinning layer.
[0076] The writing method of the magnetic storage device of the present application is introduced as follows:
[0077] The writing of the magnetic memory of the present application can be realized by two different current application sequences, and the current application is realized by the controller of the magnetic memory, which are respectively described below:
[0078] Method 1:
[0079] like Figure 6 As shown, the first current application sequence includes four steps:
[0080] 1. At time t, a SOT current of, for example, 100uA and 2ns is applied along the x direction to the strong spin-orbit coupling layer to produce a SOT effect;
[0081] 2. At time t+1ns, a STT current of, for example, 100uA and 2ns is applied to the selected MTJ along the z direction to generate an STT effect;
[0082] 3. At t+2ns, remove the SOT current;
[0083] 4. At t+3ns, remove the STT current.
[0084] Method 2:
[0085] like Figure 7 As shown, the second current application sequence includes four steps:
[0086] 1. At time t, an STT current of, for example, 100uA and 2ns is applied to the selected MTJ along the z direction to generate an STT effect;
[0087] 2. At time t+1ns, a SOT current of, for example, 100uA and 2ns is applied along the x direction to the strong spin-orbit coupling layer to generate a SOT effect;
[0088] 3. At t+2ns, remove the STT current;
[0089] 4. At t+3ns, remove the SOT current.
[0090] The above writing method is described in detail below in combination with the change process of the magnetization direction of the free layer:
[0091] First, we will take the current application sequence of method 1 as an example:
[0092] like Figure 8As shown, after step 1 is executed, a SOT torque in the -y direction is generated on the magnetization direction of the free layer. Under the action of the SOT torque, the magnetization directions of the first magnetic layer and the second magnetic layer are offset in the -y direction. After step 2 is executed, an STT torque in the -x direction is applied to the magnetization direction of the free layer. Under the action of the SOT torque and the STT torque, the magnetization direction of the second magnetic layer is offset in the -y direction, and the magnetization direction of the first magnetic layer is offset to the upper left. After step 3 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are changed again. After step 4 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are flipped.
[0093] Alternatively, in the above process, the directions of the SOT current and the STT current may be opposite, or the positive and negative polarities of the two currents may be opposite. Then, the direction of the SOT torque generated in step 1 is along the y direction; the direction of the STT torque generated in step 2 is along the x direction.
[0094] Correspondingly, such as Fig. 9 As shown, after step 1 is executed, under the action of the SOT torque, the magnetization directions of the first magnetic layer and the second magnetic layer are offset to the +y direction. After step 2 is executed, under the action of the SOT torque and the STT torque, the magnetization direction of the second magnetic layer is offset to the lower right, and the magnetization direction of the first magnetic layer is offset by +y. After step 3 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are changed again. After step 4 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are flipped.
[0095] Then, we will take the current application sequence of method 2 as an example to introduce:
[0096] like Fig.10 As shown, after step 1 is executed, an STT torque in the -x direction is applied to the magnetization direction of the free layer. Under the action of the STT torque, the magnetization directions of the first magnetic layer and the second magnetic layer are offset toward the -x direction. After step 2 is executed, an SOT torque in the -y direction is applied to the magnetization direction of the free layer. Under the action of the SOT torque and the STT torque, the magnetization direction of the second magnetic layer is offset toward the -x direction, and the magnetization direction of the first magnetic layer is offset to the lower right. After step 3 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are changed again. After step 4 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are flipped.
[0097] Alternatively, in the above process, the directions of the SOT current and the STT current may be opposite, or the positive and negative polarities of the two currents may be opposite. Then, the direction of the SOT torque generated in step 1 is along the y direction; the direction of the STT torque generated in step 2 is along the x direction.
[0098] Correspondingly, such as Fig.11 As shown, after step 1 is executed, under the action of the STT torque, the magnetization directions of the first magnetic layer and the second magnetic layer are offset in the x direction. After step 2 is executed, under the action of the SOT torque and the STT torque, the magnetization direction of the second magnetic layer is offset to the upper left, and the magnetization direction of the first magnetic layer is offset in the x direction. After step 3 is executed, under the action of the SOT torque, the magnetization directions of the first magnetic layer and the second magnetic layer are changed again. After step 4 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are flipped.
[0099] If the magnetization direction of the free layer needs to be reversed again, the writing method of the above method 1 or method 2 can be performed again, and the directions of the SOT current and the STT current can be opposite to the directions at the time of the last reversal or remain unchanged.
[0100] In another possible implementation, Fig.12 As shown, the MTJ in the magnetic memory of the present application can also be circular or square, wherein the magnetization direction of the pinned layer is perpendicular to the upper and lower surfaces of the MTJ, and the easy axis of the magnetization direction of the free layer and the direction of the STT current have an angle other than 90 degrees in the yz plane.
[0101] The following is an introduction to the reversal process of the magnetization direction of the free layer achieved in this way:
[0102] Take the current application sequence of method 2 as an example. Fig.13 As shown, after step 1 is executed, an STT torque in the -z direction is applied to the magnetization direction of the free layer. Under the action of the STT torque, the magnetization directions of the first magnetic layer and the second magnetic layer are offset in the -z direction. After step 2 is executed, an SOT torque in the -y direction is applied to the magnetization direction of the free layer. Under the action of the SOT torque and the STT torque, the magnetization direction of the second magnetic layer is offset in the -z direction, and the magnetization direction of the first magnetic layer is offset to the upper left. After step 3 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are changed again. After step 4 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are flipped.
[0103] Alternatively, in the above process, the directions of the SOT current and the STT current may be opposite, or the positive and negative polarities of the two currents may be opposite. Then, the direction of the STT torque generated in step 1 is along the z direction; the direction of the SOT torque generated in step 2 is along the y direction.
[0104] Correspondingly, such as Fig.14As shown in the figure, after step 1 is executed, under the action of the SOT torque, the magnetization directions of the first magnetic layer and the second magnetic layer are offset to the +z direction; after step 2 is executed, under the action of the SOT torque and the STT torque, the magnetization direction of the second magnetic layer is offset to the lower right, and the magnetization direction of the first magnetic layer is offset by +z. After step 3 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are changed again. After step 4 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are flipped.
[0105] Take the current application sequence of method 1 as an example. Fig.15 As shown, after step 1 is executed, a SOT torque in the -y direction is applied to the magnetization direction of the free layer. Under the action of the SOT torque, the magnetization directions of the first magnetic layer and the second magnetic layer are offset in the -y direction; after step 2 is executed, a STT torque in the -z direction is applied to the magnetization direction of the free layer. Under the action of the SOT torque and the STT torque, the magnetization direction of the second magnetic layer is offset in the -y direction, and the magnetization direction of the first magnetic layer is offset to the lower right. After step 3 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are changed again. After step 4 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are flipped.
[0106] Alternatively, in the above process, the directions of the SOT current and the STT current may be opposite, or the positive and negative polarities of the two currents may be opposite. Then, the direction of the SOT torque generated in step 1 is along the y direction; the direction of the STT torque generated in step 2 is along the z direction.
[0107] Correspondingly, such as Fig.16 As shown in the figure, after step 1 is executed, under the action of the SOT torque, the magnetization directions of the first magnetic layer and the second magnetic layer are offset in the z direction; after step 2 is executed, under the action of the SOT torque and the STT torque, the magnetization direction of the second magnetic layer is offset to the lower right, and the magnetization direction of the first magnetic layer is offset in the z direction. After step 3 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are changed again. After step 4 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are flipped.
[0108] Of course, in another possible implementation, the easy axis of the magnetization direction of the free layer may also be along the direction of the STT current, and the magnetization direction of the pinned layer has an angle of non-90 degrees with the easy axis in the yz plane. Alternatively, the easy axis of the magnetization direction of the free layer has an angle of non-90 degrees with the direction of the STT current in the yz plane, and the magnetization direction of the pinned layer has an angle with the easy axis in the yz plane, and has an angle of non-90 degrees with the direction of the STT current.
[0109] Case 2: The SOT torque acts on the magnetization direction of the bottom magnetic layer, and the STT torque acts on the magnetization direction of the top magnetic layer.
[0110] In this implementation, the magnetic memory of the present application can make the SOT torque mainly act on the magnetization direction of the bottom magnetic layer, and the STT torque mainly act on the magnetization direction of the upper magnetic layer by thickening the thickness of the free layer. In this implementation, the shape of the MTJ is elliptical, and the long axis of the MTJ is parallel to the direction of the SOT current or there is an angle of not 90 degrees, and the easy axis of the magnetization direction of the free layer and the magnetization direction of the pinned layer are both along the long axis of the MTJ. Alternatively, the magnetization direction of the pinned layer can also be at an angle with the long axis direction of the MTJ, and it is only necessary to ensure that the direction of the STT torque is on one side of the long axis of the MTJ and has an angle less than or equal to 90 degrees with the long axis, and the direction of the SOT torque is respectively toward the two sides of the vertical line of the midpoint of the long axis of the MTJ, and the direction of the SOT torque is toward the other side of the long axis of the MTJ.
[0111] The following is a detailed example:
[0112] like Fig.17 As shown, another implementation form of the magnetic memory of the present application, in which the long axis of the MTJ and the direction of the SOT current have an angle of, for example, 45 degrees, the magnetization direction of the pinned layer is along the y-axis, and the thickness of the free layer is thickened to achieve that the SOT torque mainly acts on the magnetization direction of the bottom magnetic layer, and the STT torque mainly acts on the magnetization direction of the upper magnetic layer. The following is an introduction to the reversal process of the magnetization direction of the free layer of this implementation:
[0113] Take the current application sequence of method 1 as an example. Fig.18 As shown, after step 1 is executed, a SOT torque in the -y direction is applied to the magnetization direction of the free layer. Under the action of the SOT torque, the magnetization direction of the first magnetic layer shifts toward the -y direction. After step 2 is executed, a STT torque in the y direction is applied to the magnetization direction of the free layer. Under the action of the SOT torque and the STT torque, the magnetization directions of the first magnetic layer and the second magnetic layer change again. After step 3 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer change again. After step 4 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are flipped.
[0114] In the above implementation, if Fig.19 As shown in , if the magnetization direction of the free layer needs to be flipped again, the directions of the applied SOT current and STT current cannot be the same as those of the previous flip, otherwise the flip cannot be completed. Fig.20a As shown, after the directions of the applied SOT current and STT current are reversed, the magnetization direction of the free layer can be reversed again.
[0115] Take the current application sequence of method 2 as an example. Fig.20b As shown, after step 1 is executed, an STT torque in the y direction is applied to the magnetization direction of the free layer. Under the action of the STT torque, the magnetization direction of the second magnetic layer shifts toward the y direction. After step 2 is executed, an SOT torque in the -y direction is applied to the magnetization direction of the free layer. Under the action of the SOT torque and the STT torque, the magnetization directions of the first magnetic layer and the second magnetic layer change again. After step 3 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer change again. After step 4 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are flipped.
[0116] In the above implementation, if the magnetization direction of the free layer needs to be flipped again, the directions of the applied SOT current and STT current cannot be the same as those of the previous flip, otherwise the flip cannot be completed. Fig.20c As shown, after the directions of the applied SOT current and STT current are reversed, the magnetization direction of the free layer can be reversed again.
[0117] like Fig.21 As shown, another implementation form of the magnetic memory of the present application, in which the long axis of the MTJ and the direction of the SOT current have an angle of, for example, 45 degrees, the magnetization direction of the pinned layer is along the easy axis, and the thickness of the free layer is also thickened to achieve that the SOT torque mainly acts on the magnetization direction of the bottom magnetic layer, and the STT torque mainly acts on the magnetization direction of the upper magnetic layer. The following is an introduction to the reversal process of the magnetization direction of the free layer of this implementation:
[0118] Take the current application sequence of method 1 as an example. Fig. 22 As shown, after step 1 is executed, a SOT torque in the -y direction is applied to the magnetization direction of the free layer. Under the action of the SOT torque, the magnetization direction of the first magnetic layer shifts toward the -y direction. After step 2 is executed, an STT torque in the x direction is applied to the magnetization direction of the free layer. Under the action of the SOT torque and the STT torque, the magnetization directions of the first magnetic layer and the second magnetic layer change again. After step 3 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer change again. After step 4 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are flipped.
[0119] In the above implementation, if the magnetization direction of the free layer needs to be flipped again, the directions of the applied SOT current and STT current cannot be the same as those of the previous flip, otherwise the flip cannot be completed. Fig.23 As shown, after the directions of the applied SOT current and STT current are reversed, the magnetization direction of the free layer can be reversed again.
[0120] like Fig.24 As shown, it is another implementation form of the magnetic memory of the present application. In this implementation, the long axis of the MTJ and the magnetization direction of the pinned layer are along the direction of the SOT current, and the thickness of the free layer is also thickened to achieve that the SOT torque mainly acts on the magnetization direction of the bottom magnetic layer, and the STT torque mainly acts on the magnetization direction of the upper magnetic layer. The following is an introduction to the reversal process of the magnetization direction of the free layer of this implementation:
[0121] Take the current application sequence of method 1 as an example. Fig.25 As shown, after step 1 is executed, a SOT torque in the -y direction is applied to the magnetization direction of the free layer. Under the action of the SOT torque, the magnetization direction of the first magnetic layer is offset in the -y direction, and the magnetization direction of the second magnetic layer is offset in the y direction. After step 2 is executed, an STT torque in the x direction is applied to the magnetization direction of the free layer. Under the action of the SOT torque and the STT torque, the magnetization directions of the first magnetic layer and the second magnetic layer are changed again. After step 3 is executed, the magnetization direction of the first magnetic layer is changed again. After step 4 is executed, the magnetization directions of the first magnetic layer and the second magnetic layer are flipped.
[0122] In the above implementation, if the magnetization direction of the free layer needs to be flipped again, the directions of the applied SOT current and STT current cannot be the same as those of the previous flip, otherwise the flip cannot be completed. Fig.26 As shown, after the directions of the applied SOT current and STT current are reversed, the magnetization direction of the free layer can be reversed again.
[0123] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.
[0124] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.
[0125] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
[0126] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.
[0127] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, read-only memory), random access memory (RAM, random access memory), disk or optical disk and other media that can store program code.
Claims
1. A magnetic memory, comprising a strong spin-orbit coupling layer and a plurality of magnetic tunnel junctions (MTJs) disposed on the strong spin-orbit coupling layer, wherein each of the plurality of MTJs comprises a free layer, an insulating layer and a pinned layer, It is characterized in that The free layer includes a first magnetic layer, a second magnetic layer and a spacer layer.
2. The magnetic memory according to claim 1, It is characterized in that The first magnetic layer and the second magnetic layer form an antiferromagnetic coupling.
3. The magnetic memory according to claim 1 or 2, It is characterized in that The MTJ is elliptical, and the long axis of the MTJ is parallel to or at an angle other than 90 degrees with the direction of the spin-orbit moment SOT current applied to the strong spin-orbit coupling layer.
4. The magnetic memory according to claim 3, It is characterized in that The magnetization direction of the free layer is along the long axis of the MTJ, and the magnetization direction of the pinned layer is along the long axis of the MTJ, or has an angle with the long axis of the MTJ.
5. The magnetic memory according to claim 1 or 2, It is characterized in that The MTJ is circular or square; The magnetization direction of the free layer and / or the magnetization direction of the pinned layer forms an angle other than 90 degrees with a direction of a spin transfer torque (STT) current perpendicularly flowing through the MTJ.
6. The magnetic memory according to any one of claims 1 to 5, It is characterized in that The material of the strong spin-orbit coupling layer includes one or more of platinum Pt, tungsten W, tantalum Ta, copper Cu, topological insulator, antiferromagnetic IrMn, and antiferromagnetic PtMn.
7. The magnetic memory according to any one of claims 1 to 5, It is characterized in that The materials of the first magnetic layer and the second magnetic layer include one or more of iron (Fe), cobalt (Co), nickel (Ni), CoFe, CoFeB, (Co / Pt)n, (Co / Ni)n and (Co / Pd)n.
8. The magnetic memory according to any one of claims 1 to 5, It is characterized in that The material of the spacer layer includes one or more of ruthenium Ru, niobium Nb, tantalum Ta, chromium Cr, molybdenum Mo, tungsten W, rhenium Re, osmium Os, rhodium Rh, iridium Ir, platinum Pt, copper Cu, silver Ag, and gold Au.
9. The magnetic memory according to any one of claims 1 to 5, It is characterized in that The thickness of the spacer layer is less than 5 nm.
10. A method for writing to a magnetic memory, wherein the magnetic memory is the magnetic memory according to any one of claims 1 to 9, It is characterized in that include: applying a first current; applying a second current; removing the first current; removing the second current; The first current is a spin-orbit moment SOT current applied to a strong spin-orbit coupling layer of the magnetic memory, and the second current is a spin transfer torque STT current applied to a magnetic tunnel junction MTJ to be written in the magnetic memory; Or, the second current is a SOT current applied to a strong spin-orbit coupling layer of the magnetic memory, and the first current is a STT current applied to a magnetic tunnel junction MTJ to be written in the magnetic memory.
11. An electronic device, It is characterized in that The electronic device comprises the magnetic memory according to any one of claims 1 to 9.
12. A chip, It is characterized in that The chip comprises the magnetic memory according to any one of claims 1 to 9.