Magnetoresistance effect element, magnetic memory, Magnetization reversal method, And spin current magnetization reversal element

Abstract

The present application provides a kind of magnetoresistance effect element, in the magnetoresistance effect element, it has: magnetoresistance effect element, with the first ferromagnetic metal layer of fixed magnetization direction, and the second ferromagnetic metal layer of variable magnetization direction, and the non-magnetic layer being interposed by the first ferromagnetic metal layer and the second ferromagnetic metal layer;Spin-orbit torque wiring, it extends along the direction of the cross direction of the stacking direction of the magnetoresistance effect element, and is engaged with the above-mentioned second ferromagnetic metal layer, in the part of the above-mentioned magnetoresistance effect element and the above-mentioned spin-orbit torque wiring engagement, the current that flows in the above-mentioned magnetoresistance effect element and the current that flows in the above-mentioned spin-orbit torque wiring are combined or distributed.

Description

[0001] (This application is a divisional application of patent application No. 201680068515.2, filed on November 25, 2016, entitled "Magnetoresistive Effect Element, Magnetic Storage, Magnetization Reversal Method and Spin Current Magnetization Reversal Element".) Technical Field

[0002] This invention relates to magnetoresistive elements, magnetic storage devices, magnetization reversal methods, and spin-current magnetization reversal elements that can be applied to high-frequency electronic components such as magnetic heads or high-frequency filters, as well as magnetic storage devices.

[0003] This application claims priority based on Japanese Patent Application No. 2015-232334 filed on November 27, 2015; Japanese Patent Application No. 2016-53072 filed on March 16, 2016; Japanese Patent Application No. 2016-56058 filed on March 18, 2016; Japanese Patent Application No. 2016-210531 filed on October 27, 2016; and Japanese Patent Application No. 2016-210533 filed on October 27, 2016, the contents of which are incorporated herein by reference. Background Technology

[0004] Giant magnetoresistive (GMR) devices, composed of multilayer films with ferromagnetic and non-magnetic layers, and tunnel magnetoresistive (TMR) devices, which use insulating layers (tunnel barrier layers, or barrier layers) as non-magnetic layers, are known. Generally, although the resistance of TMR devices is higher than that of GMR devices, the magnetoresistive (MR) ratio of TMR devices is greater than that of GMR devices. Therefore, TMR devices have attracted much attention as components for magnetic sensors, high-frequency components, magnetic heads, and non-volatile random access memory (MRAM).

[0005] As for writing methods for MRAM, there are known methods that use a magnetic field generated by an electric current to write (magnetization reversal) or a spin-transfer torque (STT) generated by current flowing along the stacking direction of the magnetoresistive element to write (magnetization reversal).

[0006] When using magnetic fields, problems such as the inability to write can occur when the component size is small, even with current flowing through fine wiring.

[0007] In contrast, in the spin-transfer torque (STT) method, a ferromagnetic layer (fixed layer, reference layer) spin-polarizes the current, and the spin of the current is transferred to the magnetization of another ferromagnetic layer (free layer, recording layer). The writing is performed by the torque (STT) generated at that time (magnetization reversal). It has the advantage that the smaller the device size, the smaller the current required for writing.

[0008] Existing technical documents

[0009] Non-patent literature

[0010] Non-patent literature 1: IMM Miron, K. Garello, G. Gaudin, P.-J. Zermatten, M.V. Costache, S. Auffret, S. Bandiera, B. Rodmacq, A. Schuhl, and P. Gambardella, Nature, 476, 189 (2011). Summary of the Invention

[0011] The technical problem that the invention aims to solve

[0012] From an energy efficiency perspective, magnetization reversal using STT-based TMR elements is efficient, but the reversal current density required for magnetization reversal is high.

[0013] From the perspective of long lifespan of TMR devices, the lower the reverse current density, the better. The same applies to GMR devices.

[0014] Therefore, in either the TMR element or the GMR element, it is desirable to reduce the current density flowing through the magnetoresistive element.

[0015] In recent years, it has been advocated that magnetization reversal using pure spin current generated through spin-orbit interaction (SOT) be possible in applications (e.g., non-patent literature 1). Pure spin current generated through spin-orbit interaction can induce spin-orbit torque (SOT), and magnetization reversal is caused by the magnitude of the SOT. Pure spin current is generated by the same number of upward-spinning and downward-spinning electrons flowing in opposite directions. Because the charge flows cancel each other out, the current flowing within the magnetoresistive element is zero. If magnetization reversal can be achieved solely through this pure spin current, the zero current allows for a longer lifetime of the magnetoresistive element. Alternatively, it is argued that if SOT can be utilized for magnetization reversal, and SOT based on pure spin current can also be used, the current used for SOT can be reduced to a component utilizing SOT based on pure spin current, thus achieving a longer lifetime for the magnetoresistive element. It is also believed that when both SOT and SOT are utilized, a higher proportion of SOT utilization leads to a longer lifetime for the magnetoresistive element.

[0016] This invention was made in view of the above-mentioned technical problems, and its object is to provide a spin-current magnetization reversal element, a magnetoresistive effect element, and a magnetic memory that utilize magnetization reversal generated by pure spin current. Furthermore, its object is to provide a magnetization reversal method that utilizes pure spin current to perform magnetization reversal of a magnetoresistive effect element.

[0017] To solve the above-mentioned technical problems, the present invention provides the following technical solution.

[0018] (1) A magnetoresistive effect element according to one embodiment of the present invention comprises: a magnetoresistive effect element having a first ferromagnetic metal layer with a fixed magnetization direction, a second ferromagnetic metal layer with a variable magnetization direction, and a nonmagnetic layer sandwiched between the first ferromagnetic metal layer and the second ferromagnetic metal layer; a spin-orbit torque wiring extending in a direction intersecting the stacking direction of the magnetoresistive effect element and joining with the second ferromagnetic metal layer, wherein at the junction of the magnetoresistive effect element and the spin-orbit torque wiring, the current flowing through the magnetoresistive effect element and the current flowing through the spin-orbit torque wiring are combined or distributed.

[0019] (2) In the magnetoresistive effect element described in (1) above, the spin-orbit torque wiring may also contain a non-magnetic metal with an atomic number of 39 or above that has d electrons or f electrons in the outermost layer.

[0020] (3) In the magnetoresistive effect element described in (1) or (2) above, the spin-track torque wiring may also be composed of a pure spin current generating part and a low resistance part, wherein the pure spin current generating part is composed of a material that generates pure spin current, and the low resistance part is composed of a material with a lower resistance than the pure spin current generating part, and at least a portion of the pure spin current generating part is in contact with the second ferromagnetic metal layer.

[0021] (4) In any one of (1) to (3) above, the spin-track torque wiring may also contain magnetic metal.

[0022] (5) In any of the magnetoresistive effect elements described in (1) to (4) above, a cover layer may be provided between the spin-orbit torque wiring and the second ferromagnetic metal layer, and the spin-orbit torque wiring and the second ferromagnetic metal layer may be joined via the cover layer.

[0023] (6) In any one of (1) to (5) above, the spin-track torque wiring may also have a sidewall joint that is engaged with the sidewall of the second ferromagnetic metal layer.

[0024] (7) The magnetic storage device of one embodiment of the present invention comprises a magnetoresistive effect element as described in any one of claims (1) to (6).

[0025] (8) In one embodiment of the magnetization reversal method of the present invention, in the magnetoresistive effect element described in any one of (1) to (6), the current density flowing through the spin-orbit torque wiring is less than 1 × 10⁻⁶. 7 A / cm 2 .

[0026] (9) In one embodiment of the present invention, the magnetization reversal method applies a current to the power supply of the magnetoresistive effect element after applying a current to the power supply of the spin-orbit torque wiring.

[0027] (10) A spin current magnetization reversal element according to one embodiment of the present invention comprises: a second ferromagnetic metal layer with variable magnetization direction, and a spin orbital torque wiring extending in a direction intersecting the normal direction of the second ferromagnetic metal layer and engaging with the second ferromagnetic metal layer.

[0028] The aforementioned spin-orbit torque wiring consists of a pure spin flow generating section and a low-resistance section. The pure spin flow generating section is made of a material that generates pure spin flow, and the low-resistance section is made of a material with a lower resistance than the pure spin flow generating section. At least a portion of the pure spin flow generating section is in contact with the aforementioned second ferromagnetic metal layer.

[0029] Invention Effects

[0030] The magnetoresistive element according to the present invention can reduce the reverse current density flowing through the magnetoresistive element. Attached Figure Description

[0031] Figure 1 This is a perspective view schematically illustrating a magnetoresistive effect element according to one embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram used to illustrate the spin Hall effect;

[0033] Figure 3 This is a schematic diagram illustrating one embodiment of spin-orbit torque wiring, (a) is a cross-sectional view, and (b) is a top view;

[0034] Figure 4 These are schematic diagrams used to illustrate other embodiments of spin-orbit torque wiring, (a) is a cross-sectional view, and (b) is a top view;

[0035] Figure 5 These are schematic diagrams used to illustrate other embodiments of spin-orbit torque wiring, (a) is a cross-sectional view, and (b) is a top view;

[0036] Figure 6 These are schematic diagrams used to illustrate other embodiments of spin-orbit torque wiring, (a) is a cross-sectional view, and (b) is a top view;

[0037] Figure 7 This is a schematic cross-sectional view of a magnetoresistive element according to one embodiment of the present invention obtained by cutting it with the yz plane;

[0038] Figure 8 This is a schematic cross-sectional view obtained by cutting the magnetoresistive effect element of another embodiment of the present invention with the yz plane;

[0039] Figure 9 This is a schematic cross-sectional view of a magnetoresistive element according to another embodiment of the present invention, cut by the yz plane;

[0040] Figure 10 This is a perspective view schematically illustrating a magnetoresistive effect element according to one embodiment of the present invention;

[0041] Figure 11 This is a perspective view schematically illustrating a spin-flow magnetization reversal element according to one embodiment of the present invention;

[0042] Figure 12 This is a perspective view schematically illustrating a spin-flow magnetization reversal element according to another embodiment of the present invention.

[0043] Symbol Explanation

[0044] 1...Second ferromagnetic metal layer

[0045] 2……Spin-orbit torque wiring

[0046] 10...Substrate

[0047] 20...Magnetic reluctance effect element

[0048] 21……First ferromagnetic metal layer

[0049] 22……Non-magnetic layer

[0050] 23……Second ferromagnetic metal layer

[0051] 23'……Joint (Second ferromagnetic metal layer side)

[0052] 24……Covering layer

[0053] 24'……Joint (Cover Layer Side)

[0054] 30……wiring

[0055] 40, 50, 51, 52... Spin-orbit torque wiring

[0056] 40'……Joint (Spin-orbit torque wiring side)

[0057] 41, 41A, 41B... Spin flow generation section

[0058] 42A, 42B, 42C... Low Resistance Section

[0059] 100, 200, 300... Magnetoresistive element

[0060] 101... Spin current magnetization reversal element

[0061] I……current

[0062] S1……Upward spin

[0063] S2……Downward spin

[0064] M 21 M 23 ……magnetization

[0065] I1……First Current Path

[0066] I2……Second current path

[0067] 110...First Power Supply

[0068] 120...Second power supply Detailed Implementation

[0069] The present invention will now be described in detail with appropriate reference to the accompanying drawings. To facilitate understanding of the features of the invention, the drawings used in the following description sometimes show enlarged portions of the features for convenience, and the dimensions and ratios of the constituent elements often differ from the actual dimensions. The materials, dimensions, etc., illustrated in the following description are merely examples, and the invention is not limited thereto; appropriate modifications can be made to achieve the effects of the invention.

[0070] (Magnetic reluctance element)

[0071] Figure 1 This is a perspective view schematically illustrating a magnetoresistive effect element according to one embodiment of the present invention.

[0072] A magnetoresistive effect element 100 according to one embodiment of the present invention includes: a magnetoresistive effect element 20 and a spin-orbit torque wiring 40 extending in a direction intersecting the stacking direction of the magnetoresistive effect element 20 and engaging with the magnetoresistive effect element 20.

[0073] In containing Figure 1 In the following content, as an example of a structure in which the spin-orbit torque wiring extends in a direction that intersects with the stacking direction of the magnetoresistive effect element, the case of a structure extending in an orthogonal direction will be explained.

[0074] exist Figure 1 The diagram also shows: a wiring 30 for allowing current to flow along the stacking direction of the magnetoresistive element 20, a substrate 10 forming the wiring 30, and a cover layer.

[0075] Below, the stacking direction of the magnetoresistive effect element 20 is taken as the z-direction, the direction perpendicular to the z-direction and parallel to the spin-orbit torque line 40 is taken as the x-direction, and the direction orthogonal to both the x-direction and the z-direction is taken as the y-direction.

[0076] <Magnetic Reluctance Components>

[0077] The magnetoresistive element 20 has: a first ferromagnetic metal layer 21 with a fixed magnetization direction, a second ferromagnetic metal layer 23 with a variable magnetization direction, and a nonmagnetic layer 22 sandwiched between the first ferromagnetic metal layer 21 and the second ferromagnetic metal layer 23.

[0078] The magnetization of the first ferromagnetic metal layer 21 is fixed in one direction, while the magnetization direction of the second ferromagnetic metal layer 23 changes relatively, thus functioning as a magnetoresistive effect element 20. In the case of coercivity difference type (pseudo spin valve type) MRAM, the coercivity of the first ferromagnetic metal layer is greater than that of the second ferromagnetic metal layer. In addition, in the case of exchange bias type (spin valve type) MRAM, the magnetization direction is fixed in the first ferromagnetic metal layer by exchange coupling with the antiferromagnetic layer.

[0079] Furthermore, when the non-magnetic layer 22 is made of an insulator, the magnetoresistive effect element 20 is a tunneling magnetoresistance (TMR) element, and when the non-magnetic layer 22 is made of metal, it is a giant magnetoresistance (GMR) element.

[0080] As the magnetoresistive effect element provided in this invention, a known structure of a magnetoresistive effect element can be used. For example, each layer can be composed of multiple layers, and other layers such as an antiferromagnetic layer for fixing the magnetization direction of the first ferromagnetic metal layer can also be included.

[0081] The first ferromagnetic metal layer 21 is referred to as the fixed layer or reference layer, and the second ferromagnetic metal layer 23 is referred to as the free layer or storage layer, etc.

[0082] The first ferromagnetic metal layer 21 and the second ferromagnetic metal layer 23 can be in-plane magnetized films with the magnetization direction parallel to the in-plane direction of the layer, or they can be vertical magnetized films with the magnetization direction perpendicular to the direction of the layer.

[0083] As the material for the first ferromagnetic metal layer 21, known materials can be used. For example, metals selected from Cr, Mn, Co, Fe, and Ni, and alloys containing one or more of these metals and exhibiting ferromagnetism can be used. Alternatively, alloys containing these metals and at least one of B, C, and N can also be used. Specifically, Co-Fe and Co-Fe-B are examples.

[0084] Furthermore, to achieve higher output, Hassler alloys such as Co2FeSi are preferred. Hassler alloys contain intermetallic compounds with a chemical composition of X2YZ, where X is a transition metal or noble metal element from the Co, Fe, Ni, or Cu group of the periodic table; Y is a transition metal from the Mn, V, Cr, or Ti group, or any element of X; and Z is a typical element from Groups III to V. Examples include Co2FeSi, Co2MnSi, and Co2Mn. 1-a Fe a Al b Si 1-b wait.

[0085] Furthermore, to further increase the coercivity of the first ferromagnetic metal layer 21 relative to the second ferromagnetic metal layer 23, antiferromagnetic materials such as IrMn and PtMn can be used as the material bonded to the first ferromagnetic metal layer 21. Moreover, to prevent the leakage magnetic field of the first ferromagnetic metal layer 21 from affecting the second ferromagnetic metal layer 23, a synthetic ferromagnetic coupling structure can also be employed.

[0086] Furthermore, when the magnetization direction of the first ferromagnetic metal layer 21 is made perpendicular to the stacked surface, a stacked film of Co and Pt is preferably used. Specifically, the first ferromagnetic metal layer 21 can be set as [Co(0.24nm) / Pt(0.16nm)]6 / Ru(0.9nm) / [Pt(0.16nm) / Co(0.16nm)]4 / Ta(0.2nm) / FeB(1.0nm).

[0087] As the material for the second ferromagnetic metal layer 23, ferromagnetic materials, especially soft magnetic materials, can be used. For example, metals selected from Cr, Mn, Co, Fe, and Ni, alloys containing one or more of these metals, and alloys containing these metals and at least one of B, C, and N can be used. Specifically, examples include Co-Fe, Co-Fe-B, and Ni-Fe.

[0088] When the magnetization direction of the second ferromagnetic metal layer 23 is made perpendicular to the stacking surface, it is preferable to set the thickness of the second ferromagnetic metal layer to 2.5 nm or less. Perpendicular magnetic anisotropy can be applied to the second ferromagnetic metal layer 23 at the interface between the second ferromagnetic metal layer 23 and the non-magnetic layer 22. Furthermore, since the effect of perpendicular magnetic anisotropy is attenuated by increasing the thickness of the second ferromagnetic metal layer 23, it is preferable that the thickness of the second ferromagnetic metal layer 23 be as thin as possible.

[0089] As the non-magnetic layer 22, known materials can be used.

[0090] For example, when the non-magnetic layer 22 is composed of an insulator (in the case of a tunneling barrier layer), materials such as Al2O3, SiO2, Mg, and MgAl2O4O can be used. Alternatively, materials such as Zn and Be can be used, where some of Al, Si, and Mg are replaced. Among these, MgO or MgAl2O4 are materials capable of coherent tunneling, thus enabling efficient spin injection.

[0091] Alternatively, if the non-magnetic layer 22 is made of metal, Cu, Au, Ag, etc. can be used as its material.

[0092] In addition, such as Figure 1 As shown, a capping layer 24 is preferably formed on the surface of the second ferromagnetic metal layer 23 opposite to the non-magnetic layer 22. The capping layer 24 can suppress the diffusion of elements from the second ferromagnetic metal layer 23. In addition, the capping layer 24 also helps the crystal orientation of each layer of the magnetoresistive effect element 20. As a result, by providing the capping layer 24, the magnetism of the first ferromagnetic metal layer 21 and the second ferromagnetic metal layer 23 of the magnetoresistive effect element 20 can be stabilized, and the resistance of the magnetoresistive effect element 20 can be reduced.

[0093] The capping layer 24 preferably uses a material with high conductivity. For example, Ru, Ta, Cu, Ag, Au, etc. can be used. The crystal structure of the capping layer 24 is preferably set according to the crystal structure of the adjacent ferromagnetic metal layer, and is appropriately set as an fcc structure, hcp structure, or bcc structure.

[0094] Furthermore, the capping layer 24 is preferably selected from silver, copper, magnesium, and aluminum. Details will be described later, but when the spin-orbit torque wiring 40 and the magnetoresistive effect element 20 are connected via the capping layer 24, it is preferable that the capping layer 24 does not dissipate the spin propagating from the spin-orbit torque wiring 40. Also, materials such as silver, copper, magnesium, and aluminum have spin diffusion lengths of 100 nm or more, making spin dissipation difficult.

[0095] The thickness of the capping layer 24 is preferably less than or equal to the spin diffusion length of the material constituting the capping layer 24. If the thickness of the capping layer 24 is less than or equal to the spin diffusion length, the spin propagating from the spin-orbit torque wiring 40 can be sufficiently transmitted to the magnetoresistive effect element 20.

[0096] <Spin-orbit torque wiring>

[0097] The spin-orbit torque wiring extends in a direction that intersects the stacking direction of the magnetoresistive effect elements. The spin-orbit torque wiring is electrically connected to a power source that allows current to flow through it in a direction orthogonal to the stacking direction of the magnetoresistive effect elements, and together with the power source, functions as a spin injection unit that injects pure spin current into the magnetoresistive effect elements.

[0098] The spin-orbit torque wiring 40 can be directly connected to the second ferromagnetic metal layer 23, or it can be connected as follows: Figure 1 As shown, it is connected to the second ferromagnetic metal layer 23 via other layers, such as the cover layer 24.

[0099] The spin-orbit torque distribution is composed of a material that generates a pure spin current through the spin Hall effect when an electric current is applied. As such a material, any material with a structure that generates a pure spin current in the spin-orbit torque distribution is sufficient. Therefore, it is not limited to a material composed of a single element; it can also be a material composed of portions consisting of materials that generate a pure spin current and portions consisting of materials that do not generate a pure spin current.

[0100] The so-called spin Hall effect refers to the phenomenon that when an electric current is passed through a material, a pure spin current is induced in a direction orthogonal to the direction of the current, based on the interaction between the spin and orbital.

[0101] Figure 2 This is a schematic diagram used to illustrate the spin Hall effect. Based on Figure 2 The mechanism by which pure spin flow is generated through the spin Hall effect is explained.

[0102] like Figure 2 As shown, when a current I is applied along the extension direction of the spin-orbit torque wiring 40, the upward spin S + (S1) and downward spin S - (S2) then bend in the direction orthogonal to the current. The ordinary Hall effect and the spin Hall effect are the same in that the moving (moving) charge (electron) bends the direction of motion (movement), but the ordinary Hall effect is that the moving charged particle in the magnetic field is bent in the direction of motion by the Lorentz force, while in the spin Hall effect, although there is no magnetic field, the direction of motion is bent by the movement of electrons alone (by the flow of current alone), which is a big difference between the two.

[0103] In nonmagnetic materials (materials that are not ferromagnetic), due to the upward spin S + The number of electrons and the downward spin S - Since the number of electrons is equal, in the diagram, the upward-spin S is the one that moves upward. + The number of electrons and the downward spin S - The number of electrons is equal. Therefore, the net current as charge is zero. The spin current without this current is specifically called a pure spin current.

[0104] In contrast, when an electric current is passed through a ferromagnetic material, the upward-spin electrons and downward-spin electrons also bend in opposite directions, which is the same in this respect. However, in a ferromagnetic material, because one of the upward-spin electrons or the downward-spin electrons is more prevalent, a net charge flow (voltage) is generated as a result, which is different in this respect. Therefore, materials used for spin-orbit torque wiring do not include materials composed solely of ferromagnetic materials.

[0105] Here, when the upward spin S + The electron flow is represented by J ↑ , will spin downwards S - The electron flow is represented by J ↓ Represent the spin flow as J S At that time, by J S =J ↑ -J ↓ To define. In Figure 2 In the middle, as a pure spin flow, J S It flows upwards in the direction shown in the diagram. Here, J S It is an electron flow with a polarizability of 100%.

[0106] exist Figure 2 When the ferromagnetic body comes into contact with the upper surface of the spin-orbit torque wiring 40, the pure spin current diffuses and flows into the ferromagnetic body.

[0107] In this invention, by configuring a structure in which a pure spin current is generated by passing an electric current through the spin-orbit torque wiring, and the pure spin current diffuses into a second ferromagnetic metal layer connected to the spin-orbit torque wiring, it can be used as an auxiliary or main mechanism for magnetization reversal of the ferromagnetic metal layer in existing magnetoresistive effect elements utilizing STT, and can also be used in novel magnetoresistive effect elements that perform magnetization reversal of the ferromagnetic metal layer solely through SOT based on pure spin current.

[0108] As methods to assist in magnetization reversal, known methods include applying an external magnetic field, applying a voltage, heating, and utilizing material deformation. However, methods involving applying an external magnetic field, applying a voltage, and heating require external rewiring, heat sources, etc., complicating the component configuration. Furthermore, methods utilizing material deformation are difficult to control once deformation occurs during use, resulting in uncontrollable magnetization reversal.

[0109] The spin-orbit torque wiring 40 may also contain non-magnetic heavy metals. Here, "heavy metal" refers to a metal with a specific gravity greater than yttrium. The spin-orbit torque wiring 40 may also be composed solely of non-magnetic heavy metals.

[0110] In this case, the non-magnetic heavy metal is preferably a non-magnetic metal with an atomic number of 39 or higher that has d or f electrons in its outermost shell. This is because such non-magnetic metals produce a greater spin-orbit interaction in the spin Hall effect. The spin-orbit torque wiring 40 can also be composed solely of a non-magnetic metal with an atomic number of 39 or higher that has d or f electrons in its outermost shell.

[0111] Normally, when an electric current is passed through a metal, all electrons, regardless of their spin direction, move in the opposite direction to the current. In contrast, non-magnetic metals with larger atomic numbers and d or f electrons in their outermost shell exhibit stronger spin-orbit interactions. Therefore, through the spin Hall effect, the direction of electron movement depends on the electron's spin direction, easily generating a pure spin current. S .

[0112] Alternatively, the spin-orbit torque wiring 40 may also contain a magnetic metal. Magnetic metal refers to ferromagnetic or antiferromagnetic metals. This is because when a non-magnetic metal contains trace amounts of magnetic metal, the spin-orbit interaction is enhanced, increasing the spin current generation efficiency relative to the current flowing through the spin-orbit torque wiring 40. The spin-orbit torque wiring 40 may also be composed solely of an antiferromagnetic metal.

[0113] Because spin-orbit interaction is generated through the inherent internal field of the material in the spin-orbit torque wiring, even non-magnetic materials can generate pure spin current. When a trace amount of magnetic metal is added to the spin-orbit torque wiring material, the magnetic metal itself scatters the spin of the flowing electrons, thus increasing the spin current generation efficiency. However, when the amount of magnetic metal added is excessively increased, the generated pure spin current is scattered by the added magnetic metal, resulting in an enhanced reduction in spin current. Therefore, the molar ratio of the magnetic metal that can be added is preferably sufficiently smaller than the molar ratio of the main component of the pure spin generation section in the spin-orbit torque wiring. In summary, the molar ratio of the magnetic metal that can be added is preferably 3% or less.

[0114] Alternatively, the spin-orbit torque wiring 40 may also contain a topological insulator. The spin-orbit torque wiring 40 may also consist solely of a topological insulator. A topological insulator is a substance that, while internally an insulator or a high-resistivity material, exhibits a metallic state with spin polarization on its surface. It possesses spin-orbit interactions, much like an internal magnetic field. Therefore, even without an external magnetic field, it will exhibit a new topological phase due to the effects of spin-orbit interactions. This is the topological insulator, which, through strong spin-orbit interactions and the breaking of inversion symmetry at its edges, can efficiently generate pure spin currents.

[0115] As topological insulators, SnTe and Bi are preferred, for example. 1.5 Sb 0.5 Te 1.7 Se 1.3 ,TlBiSe2,Bi2Te3,(Bi 1-x Sb x )2Te3, etc. These topological insulators can generate spin currents with high efficiency.

[0116] <Substrate>

[0117] The substrate 10 preferably has excellent flatness. To obtain a surface with excellent flatness, materials such as Si and AlTiC can be used.

[0118] A substrate layer (not shown) may also be formed on the surface of the substrate 10 on the side of the magnetoresistive element 20. When a substrate layer is provided, the crystallinity, such as the crystal orientation and crystal grain size, of each layer stacked on the substrate 10, including the first ferromagnetic metal layer 21, can be controlled.

[0119] The substrate layer preferably has insulating properties. This is to prevent current flowing in the wiring 30, etc., from being dissipated. Various materials can be used as the substrate layer.

[0120] For example, as an example, the base layer may use a NaCl structure with (001) orientation and contain a nitride layer of at least one element selected from Ti, Zr, Nb, V, Hf, Ta, Mo, W, B, Al, Ce.

[0121] As another example, the substrate layer may be a perovskite-based conductive oxide layer with a (002) orientation represented by the composition formula of ABO3. Here, site A contains at least one element selected from Sr, Ce, Dy, La, K, Ca, Na, Pb, and Ba, and site B contains at least one element selected from Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Nb, Mo, Ru, Ir, Ta, Ce, and Pb.

[0122] As another example, the substrate layer may use a NaCl structure with (001) orientation and contain an oxide layer of at least one element selected from Mg, Al, and Ce.

[0123] As another example, the substrate layer may be a tetragonal or cubic crystal structure with (001) orientation and containing at least one element selected from Al, Cr, Fe, Co, Rh, Pd, Ag, Ir, Pt, Au, Mo, W.

[0124] Furthermore, the substrate layer is not limited to a single layer; multiple layers as described above can be stacked. By designing the structure of the substrate layer, the crystallinity of each layer of the magnetoresistive element 20 can be improved, and its magnetic properties can be enhanced.

[0125] Wiring

[0126] Wiring 30 is electrically connected to the first ferromagnetic metal layer 21 of the magnetoresistive effect element 20, in Figure 1 In the circuit, wiring 30, spin-orbit torque wiring 40, and power supply (not shown) form a closed loop, and the current flows along the stacking direction of the magnetoresistive effect element 20.

[0127] For wiring 30, any material with high conductivity can be used. For example, aluminum, silver, copper, gold, etc.

[0128] Figures 3-6 These are schematic diagrams illustrating an implementation of a spin-orbit torque wiring method. (a) is a cross-sectional view, and (b) is a top view.

[0129] In the magnetoresistive effect element of the present invention, even in the structure where magnetization reversal of the magnetoresistive effect element is performed solely by SOT based on pure spin current (hereinafter, sometimes referred to as "SOT-only" structure), in the magnetoresistive effect element utilizing existing STT, even in the structure where SOT based on pure spin current is used simultaneously (hereinafter, sometimes referred to as "STT and SOT combined" structure), the current flowing in the spin-orbit torque wiring (hereinafter, sometimes referred to as "SOT reversal current") is a normal current accompanying the flow of charge, so Joule heating is generated once current is applied.

[0130] Figures 3-6 The embodiment of the spin-orbit torque wiring shown is an example of a structure that reduces Joule heating generated by the SOT reversal current through a structure other than the materials described above.

[0131] In the "combined STT and SOT" structure, the current flowing through the magnetization reversal of the magnetoresistive effect element for the present invention includes, in addition to the current flowing directly in the magnetoresistive effect element to utilize the STT effect (hereinafter sometimes referred to as "STT reversal current"), the current flowing in the spin-orbit torque wiring to utilize the SOT effect ("SOT reversal current"). Both currents are ordinary currents accompanied by the flow of charge, so Joule heating is generated once current is applied.

[0132] In this structure, because both STT-based and SOT-based magnetization reversal are used simultaneously, the STT reversal current is reduced compared to a structure that performs magnetization reversal solely through the STT effect, but the energy required to achieve the same level of SOT reversal current is consumed.

[0133] Heavy metals, as materials capable of generating pure spin currents, have higher resistance than metals used in conventional wiring.

[0134] Therefore, from the viewpoint of reducing Joule heating based on SOT reversal current, it is more preferable for the spin-orbit torque wiring to be composed entirely of materials capable of generating pure spin current, to have a portion with low resistance. That is, from this viewpoint, the spin-orbit torque wiring is preferably composed of a portion made of a material that generates pure spin current (spin current generating section) and a portion made of a material with a resistance lower than that of the spin current generating section (low resistance section).

[0135] The spin flow generating section can be made of any material capable of generating pure spin flow; for example, it can also be a structure composed of multiple materials.

[0136] The low-resistance section can use materials commonly used for wiring. For example, aluminum, silver, copper, gold, etc. can be used. The low-resistance section only needs to be made of materials with a resistance lower than that of the spin current generating section; for example, a structure composed of multiple materials can also be used.

[0137] Furthermore, pure spin current can also be generated in the low-resistance section. In this case, the difference between the spin current generating section and the low-resistance section is that the portion composed of the material described in this specification as the material used for both the spin current generating section and the low-resistance section can be distinguished as either the spin current generating section or the low-resistance section. In addition, the portion other than the main portion that generates pure spin current, that is, the portion with a resistance lower than that of the main portion, can be distinguished as the low-resistance section from the spin current generating section.

[0138] The spin flow generating section may also contain non-magnetic heavy metals. In this case, it is sufficient to contain only a limited amount of heavy metals capable of generating pure spin flow. Furthermore, in this case, the spin flow generating section is a region where the concentration of heavy metals capable of generating pure spin flow is sufficiently small compared to the main component of the spin flow generating section, or preferably, the heavy metals capable of generating pure spin flow are the main component, for example, 90% or more. In this case, the heavy metals capable of generating pure spin flow are preferably 100% non-magnetic metals with an atomic number of 39 or more that have d or f electrons in their outermost shell.

[0139] Here, the region where the concentration of heavy metal capable of generating pure spin flow is sufficiently small compared to the main component of the spin flow generating section refers, for example, to a spin flow generating section where copper is the main component, where the concentration of heavy metal, in molar ratio, is 10% or less. When the main component constituting the spin flow generating section is composed of substances other than the aforementioned heavy metal, the concentration of heavy metal contained in the spin flow generating section, in molar ratio, is preferably 50% or less, more preferably 10% or less. These concentration regions are areas where the spin scattering effect of electrons can be effectively obtained. When the concentration of heavy metal is low, light metals with atomic numbers smaller than the heavy metal become the main component. Furthermore, in this case, it is assumed that the heavy metal does not form an alloy with the light metal, but rather that the atoms of the heavy metal are randomly dispersed within the light metal. In the light metal, because the spin-orbit interaction is weak, it is difficult to generate pure spin flow through the spin Hall effect. However, when electrons pass through the heavy metal in the light metal, even at the interface between the light and heavy metals, there is a spin scattering effect, so even in regions with low heavy metal concentrations, pure spin flow can be generated efficiently. When the concentration of heavy metals exceeds 50%, although the proportion of the spin Hall effect in the heavy metals increases, the interface effect between the light and heavy metals decreases, thus reducing the overall effect. Therefore, a concentration of heavy metals that allows for a sufficient degree of interface effect is preferred.

[0140] Furthermore, when the spin-orbit torque wiring described above contains a magnetic metal, the spin current generation section in the spin-orbit torque wiring can be composed of an antiferromagnetic metal. Antiferromagnetic metals can achieve the same effect as heavy metals that are 100% non-magnetic metals with atomic number 39 or higher and possessing d or f electrons in their outermost shell. For example, IrMn and PtMn are preferred antiferromagnetic metals, with thermally stable IrMn being more preferred.

[0141] Furthermore, when the spin-orbit torque wiring described above contains a topological insulator, the spin current generation section of the spin-orbit torque wiring can be constructed from a topological insulator. SnTe and Bi are preferred as topological insulators, for example. 1.5 Sb 0.5 Te 1.7 Se 1.3 ,TlBiSe2,Bi2Te3,(Bi 1-x Sb x )2Te3, etc. These topological insulators can efficiently generate spin currents.

[0142] In order for the pure spin current generated by the spin-orbit torque wiring to effectively diffuse into the magnetoresistive element, at least a portion of the spin current generating section needs to be in contact with the second ferromagnetic metal layer. In the case of a capping layer, at least a portion of the spin current generating section needs to be in contact with the capping layer. Figures 3-6 The embodiments of the spin-orbit torque wiring shown are all structures in which at least a portion of the spin flow generating part is in contact with the second ferromagnetic metal layer.

[0143] exist Figure 3 In the embodiment shown, the spin-orbit torque wiring 40 adopts a structure in which the junction 40' with the second ferromagnetic metal layer is composed of a spin flow generating part 41, and the spin flow generating part 41 is sandwiched between the low resistance parts 42A and 42B.

[0144] Here, when the spin current generating section and the low resistance section are electrically connected in parallel, the current flowing in the spin-orbit torque wiring flows through each part in a proportion inversely proportional to the resistance of the spin current generating section and the low resistance section.

[0145] From the perspective of pure spin current generation efficiency relative to SOT reverse current, in order to ensure that all the current flowing through the spin orbit torque wiring flows through the spin current generation section, the spin current generation section and the low resistance section are not electrically connected in parallel, but are all electrically connected in series.

[0146] Figures 3-6The spin-orbit torque wiring shown is a structure in which the spin current generation section and the low resistance section are connected in parallel without electricity when viewed from the stacking direction of the magnetoresistive effect elements. Among the structures with the cross-section shown in (a), it is the structure with the highest pure spin current generation efficiency relative to the SOT reverse current.

[0147] Figure 3 The spin-orbit torque wiring 40 shown has the following structure: when viewed from the stacking direction of the magnetoresistive effect element 20, its spin current generating portion 41 overlaps with a joint 23' including the second ferromagnetic metal layer 23, and its thickness direction is composed only of the spin current generating portion 41. In the direction of current flow, the low resistance portions 42A and 42B are arranged to sandwich the spin current generating portion 41. Figure 3 In the modified example of the spin-orbit torque wiring shown, when viewed from the stacking direction of the magnetoresistive effect elements, the spin current generation portion overlaps with the junction of the second ferromagnetic metal layer. In addition, it has a... Figure 3 The spin-orbit torque wiring shown has the same structure.

[0148] Figure 4 The spin-orbit torque wiring 40 shown has the following structure: when viewed from the stacking direction of the magnetoresistive effect element 20, its spin current generating part 41 overlaps with a portion of the junction 23' of the second ferromagnetic metal layer 23, and its thickness direction is only composed of the spin current generating part 41. In the direction of current flow, the low resistance parts 42A and 42B are arranged in a manner that sandwiches the spin current generating part 41.

[0149] Figure 5 The spin-orbit torque wiring 40 shown has the following structure: when viewed from the stacking direction of the magnetoresistive effect element 20, its spin current generating portion 41 overlaps with a joint 23' including the second ferromagnetic metal layer 23, and in its thickness direction, starting from the second ferromagnetic metal layer side, the spin current generating portion 41 and the low resistance portion 42C are stacked sequentially. In the direction of current flow, the low resistance portions 42A and 42B are arranged such that they sandwich the portion of the spin current generating portion 41 and the low resistance portion 42C stacked together. Figure 5 In the modified example of the spin-orbit torque wiring shown, when viewed from the stacking direction of the magnetoresistive effect elements, the spin current generation portion overlaps with the junction of the second ferromagnetic metal layer. In addition, it has a... Figure 5 The spin-orbit torque wiring shown has the same structure.

[0150] Figure 6The spin-orbit torque wiring 40 shown adopts the following structure: the spin current generating section 41 is composed of a first spin current generating section 41A, a second spin current generating section 41B, and low resistance sections 42A and 42B. The first spin current generating section 41A is formed on the entire side of the second ferromagnetic metal layer. The second spin current generating section 41B is stacked on the first spin current generating section, and when viewed from the stacking direction of the magnetoresistive effect element 20, they overlap in a manner that includes the joint 23' of the second ferromagnetic metal layer 23, and its thickness direction is composed only of the spin current generating section. The low resistance sections 42A and 42B are arranged in a manner that sandwiches the second spin current generating section 41B in the direction of current flow. Figure 6 In the modified example of the spin-orbit torque wiring shown, when viewed from the stacking direction of the magnetoresistive effect elements, the second spin current generating portion overlaps with the junction of the second ferromagnetic metal layer. Otherwise, it has a... Figure 6 The spin-orbit torque wiring shown has the same structure.

[0151] exist Figure 6 In the structure shown, because the area where the spin flow generating part 41 and the low resistance part 42 are in contact is large, the non-magnetic metal with a larger atomic number constituting the spin flow generating part 41 and the metal constituting the low resistance part 42 have a high degree of adhesion.

[0152] The magnetoresistive element of the present invention can be manufactured using known methods. Below, [details omitted]. Figures 3-6 The manufacturing method of the magnetoresistive effect element shown will be explained.

[0153] First, the magnetoresistive element 20 can be formed, for example, using a magnetron sputtering apparatus. When the magnetoresistive element 20 is a TMR element, for example, the tunnel barrier layer is formed by first sputtering a 0.4–2.0 nm thick metal thin film of aluminum and multiple non-magnetic elements as divalent cations onto a first ferromagnetic metal layer, followed by plasma oxidation or natural oxidation based on oxygen introduction, and then heat treatment. As a film formation method, in addition to magnetron sputtering, thin film fabrication methods such as vapor deposition, laser ablation, and MBE can also be used.

[0154] After the magnetoresistive effect element 20 is formed and its shape is created, it is preferable to first form the spin flow generation section 41. This is to efficiently create a structure that can suppress the scattering of pure spin flow from the spin flow generation section 41 to the magnetoresistive effect element 20 as much as possible.

[0155] After the magnetoresistive element 20 is formed and its shape is created, a photoresist or similar agent is used to fill the area around the processed magnetoresistive element 20, thereby forming a surface including the upper surface of the magnetoresistive element 20. At this point, it is preferable to planarize the upper surface of the magnetoresistive element 20. By planarizing, spin scattering at the interface between the spin current generation section 41 and the magnetoresistive element 20 can be suppressed.

[0156] Next, a film of the material from the spin flow generation section 41 is formed on the upper surface of the planarized magnetoresistive element 20. Film formation can be performed using methods such as sputtering.

[0157] Next, a resist or protective film is applied to the part where the spin flow generation part 41 is to be formed, and the unwanted part is removed by ion milling or reactive ion etching (RIE).

[0158] Next, a film of the material constituting the low-resistivity section 42 is formed using sputtering or the like, and the spin-orbit torque wiring 40 is fabricated by stripping the resist. When the shape of the spin flow generation section 41 is complex, the formation of the resist or protective film and the film formation of the spin flow generation section 41 can be performed in multiple steps.

[0159] Figure 7 This is a schematic cross-sectional view of a magnetoresistive element according to one embodiment of the present invention obtained by cutting it with the yz plane.

[0160] based on Figure 7 The function of the magnetoresistive effect element 100 according to one embodiment of the present invention will be explained.

[0161] like Figure 7 As shown, there are two types of current in the magnetoresistive element 100. One is the current I1 (STT reversal current) flowing along its stacking direction through the magnetoresistive element 20 and through the spin-orbit torque wiring 40 and wiring 30. Figure 7 In this configuration, current I1 flows sequentially through spin-orbit torque wiring 40, magnetoresistive effect element 20, and wiring 30. In this case, electrons flow sequentially through wiring 30, magnetoresistive effect element 20, and spin-orbit torque wiring 40.

[0162] The other is the current I2 (SOT reverse current) flowing along the extension direction of the spin-orbit torque wiring 40.

[0163] Currents I1 and I2 cross each other (orthogonally). At the junction of the magnetoresistive effect element 20 and the spin-orbit torque wiring 40 (symbol 24' indicates the junction on the side of the magnetoresistive effect element 20 (cover layer 24), and symbol 40' indicates the junction on the side of the spin-orbit torque wiring 40), the current flowing through the magnetoresistive effect element 20 and the current flowing through the spin-orbit torque wiring 40 will be combined or distributed.

[0164] By applying a current I1, electrons with spins oriented in the same direction as the magnetization in the first ferromagnetic metal layer (fixed layer) 21 pass through the non-magnetic layer 22 while maintaining their spin direction. These electrons then magnetize the second ferromagnetic metal layer (free layer) 23. 23 The direction relative to the magnetization M of the first ferromagnetic metal layer (fixed layer) 21 21 The torque (STT) is applied in a reversed and parallel manner.

[0165] On the other hand, current I2 corresponds to Figure 2 The current I is shown. That is, when a current I2 is applied, the upward spin S... + and downward spin S - They bend toward the ends of the spin-orbit torque wiring 40 respectively, generating a pure spin flow J. s Pure spin flow J s It is induced in a direction perpendicular to the direction of current I2 flow. That is, a pure spin flow J is generated in the z-axis or x-axis direction of the figure. s .exist Figure 7 In the diagram, only the pure spin current J in the z-axis direction, which contributes to the magnetization direction of the second ferromagnetic metal layer 23, is shown. s .

[0166] The pure spin current J generated by flowing current I2 in the spin-orbit torque wiring 40 on the front side of the figure. s The spin diffuses into the second ferromagnetic metal layer 23 through the capping layer 24, and the incoming spin magnetizes the second ferromagnetic metal layer 23. 23 It will have an impact. That is, in Figure 7 In the process, the spin flowing into the second ferromagnetic metal layer 23 in the -x direction is applied to induce magnetization M in the second ferromagnetic metal layer 23 in the +x direction. 23 The torque of magnetization reversal (SOT).

[0167] As described above, the STT effect generated by the current flowing through the first current path I1 is applied based on the pure spin current J generated by the current flowing through the second current path I2. s The SOT effect causes the magnetization M of the second ferromagnetic metal layer 23 to increase. 23 Perform magnetization reversal.

[0168] When the magnetization of the second ferromagnetic metal layer 23 is to be reversed solely through the STT effect (i.e., by allowing current I1 to flow), a voltage greater than a specified voltage needs to be applied to the magnetoresistive element 20. The typical driving voltage of a TMR element is relatively small, below a few V, but the non-magnetic layer 22 is a very thin film of about a few nm, which can sometimes lead to insulation failure. By continuously energizing the non-magnetic layer 22, weaker portions of the non-magnetic layer (poor film quality, thin film thickness, etc.) will be damaged probabilistically.

[0169] In contrast, the magnetoresistive element in the "combined STT and SOT" structure of the present invention utilizes both the STT and SOT effects. This reduces the voltage applied to the magnetoresistive element and also reduces the current density flowing through the spin-orbit torque wiring. By reducing the voltage applied to the magnetoresistive element, a longer lifespan can be achieved. Furthermore, by reducing the current density flowing through the spin-orbit torque wiring, a significant decrease in energy efficiency can be avoided.

[0170] The current density flowing through the spin-orbit torque wiring is preferably less than 1×10⁻⁶. 7 A / cm 2 When the current density flowing through the spin-orbit torque wiring is too high, heat will be generated due to the current flowing through it. When this heat is applied to the second ferromagnetic metal layer, the magnetization stability of the second ferromagnetic metal layer will be lost, sometimes resulting in unexpected magnetization reversals. When such unexpected magnetization reversals occur, problems such as rewriting the recorded information can arise. Therefore, to avoid unexpected magnetization reversals, the current density flowing through the spin-orbit torque wiring should preferably not be too high. If the current density flowing through the spin-orbit torque wiring is less than 1 × 10⁻⁶... 7 A / cm 2 This would at least prevent magnetization reversal caused by the generated heat.

[0171] Figure 8 This is a diagram illustrating a magnetoresistive element according to another embodiment of the present invention.

[0172] exist Figure 8 In the magnetoresistive effect element 200 shown, the spin-orbit torque wiring 50 has an upper surface joint portion 51 (equivalent to the spin-orbit torque wiring 40) provided in the stacking direction of the magnetoresistive effect element 20, and also has a sidewall joint portion 52 that is joined to the sidewall of the second ferromagnetic metal layer 23.

[0173] When current flows through the spin-orbit torque wiring 50, in addition to the pure spin current J generated by the upper surface joint 51, s In addition, a pure spin flow J is generated by the sidewall joint 52. s '.

[0174] Therefore, not only pure spin flow J s The current flows from the upper surface of the magnetoresistive element 20 through the capping layer 24 into the second ferromagnetic metal layer 23, and is a pure spin current J. s It also flows in from the sidewall of the second ferromagnetic metal layer 23, thus enhancing the SOT effect.

[0175] Figure 9 This is a diagram illustrating a magnetoresistive element according to another embodiment of the present invention.

[0176] exist Figure 9 In the magnetoresistive effect element 300 shown, a spin-orbit torque wiring 40 is provided on the substrate 10 side. In this case, the stacking order of the first ferromagnetic metal layer 23 as the fixed layer and the second ferromagnetic metal layer 24 as the free layer is... Figure 1 The magnetoresistive effect element 100 shown is the opposite.

[0177] Thus, the magnetoresistive element of the present invention can be a top-pin structure as shown in this structure, or it can be as shown in... Figure 1 The lower pin structure shown.

[0178] exist Figure 9 The magnetoresistive element 300 shown comprises, in sequence, a substrate 10, a spin-orbit torque wiring 40, a second ferromagnetic metal layer 23, a non-magnetic layer 22, a first ferromagnetic metal layer 21, a capping layer 24, and wiring 30. Because the second ferromagnetic metal layer 23 is stacked before the first ferromagnetic metal layer 21, it is less susceptible to effects such as lattice deformation compared to the magnetoresistive element 100. As a result, the perpendicular magnetic anisotropy of the second ferromagnetic metal layer 23 is improved in the magnetoresistive element 300. When the perpendicular magnetic anisotropy of the second ferromagnetic metal layer 23 increases, the MR ratio of the magnetoresistive element can be improved.

[0179] Figure 10 It means in Figure 1 The diagram shows a first power source 110 that allows current to flow along the stacking direction of the magnetoresistive effect element 20 in the magnetoresistive effect element 100, and a second power source 120 that allows current to flow through the spin-orbit torque wiring 40.

[0180] The first power supply 110 is connected to wiring 30 and spin-orbit torque wiring 40. The first power supply 110 is capable of controlling the current flowing along the stacking direction of the magnetoresistive effect element 100.

[0181] The second power supply 120 is connected to both ends of the spin-orbit torque wiring 40. The second power supply 120 can control the current flowing in a direction orthogonal to the stacking direction of the magnetoresistive effect element 20, that is, the current flowing through the spin-orbit torque wiring 40.

[0182] As described above, the current flowing along the stacking direction of the magnetoresistive element 20 induces STT. Conversely, the current flowing through the spin-orbit torque wiring 40 induces SOT. Both STT and SOT contribute to the magnetization reversal of the second ferromagnetic metal layer 23.

[0183] In this way, by using two power supplies to control the amount of current flowing along the stacking direction of the magnetoresistive element 20 and in a direction perpendicular to the stacking direction, the contribution rates of SOT and STT to magnetization reversal can be freely controlled.

[0184] For example, when a large current cannot be supplied to the device, the STT, which has high energy efficiency relative to magnetization reversal, can be mainly controlled. That is, the amount of current flowing from the first power supply 110 can be increased, while the amount of current flowing from the second power supply 120 can be decreased.

[0185] Furthermore, for example, in situations where a thinner device needs to be manufactured and the thickness of the non-magnetic layer 22 must be reduced, it is necessary to reduce the current flowing through the non-magnetic layer 22. In this case, it is possible to reduce the amount of current flowing from the first power supply 110 and increase the amount of current flowing from the second power supply 120, thereby increasing the contribution rate of the SOT.

[0186] The first power supply 110 and the second power supply 120 can use known power supplies.

[0187] As described above, according to one embodiment of the magnetoresistive effect element of the present invention, the contribution rates of STT and SOT can be freely controlled by the amount of current supplied from the first power supply and the second power supply. Therefore, the contribution rates of STT and SOT can be freely controlled according to the performance required by the device, and it can function as a highly versatile magnetoresistive effect element.

[0188] (Magnetic storage)

[0189] The magnetic RAM of the present invention includes a plurality of magnetoresistive elements of the present invention.

[0190] (Magnetic reversal method)

[0191] One embodiment of the magnetization reversal method of the present invention involves setting the current density flowing through the spin-orbit torque wiring in the magnetoresistive effect element of the present invention to be less than 1 × 10⁻⁶. 7 A / cm 2 The method.

[0192] When the current density flowing through the spin-orbit torque wiring is too high, heat will be generated due to the current flowing in the wiring. When heat is applied to the second ferromagnetic metal layer, the magnetization stability of the second ferromagnetic metal layer will be lost, sometimes resulting in unexpected magnetization reversals. When such unexpected magnetization reversals occur, the recorded information will be rewritten. Therefore, to avoid unexpected magnetization reversals, it is preferable that the current density flowing through the spin-orbit torque wiring not be too high. If the current density flowing through the spin-orbit torque wiring is less than 1 × 10⁻⁶... 7 A / cm 2 This would at least prevent magnetization reversal caused by the generated heat.

[0193] One embodiment of the magnetization reversal method of the present invention is a method of applying current to the power supply of the magnetoresistive effect element after applying current to the power supply of the spin-orbit torque wiring in the magnetoresistive effect element of the present invention.

[0194] The auxiliary process and the magnetization reversal process can be performed simultaneously, or the magnetization reversal process can be added after the auxiliary process has been performed first. That is, in Figure 7 In the magnetoresistive effect element 200 shown, current can be supplied simultaneously from the first power supply 110 and the second power supply 120, or current can be supplied from the first power supply 110 after current is supplied from the second current 120. However, to more reliably obtain the auxiliary effect of magnetization reversal utilizing SOT, it is preferable to apply current to the power supply of the magnetoresistive effect element after applying current to the power supply of the spin-orbit torque wiring. That is, it is preferable to supply current from the first power supply 110 after current is supplied from the second current 120.

[0195] (Spin current magnetization reversal element)

[0196] Figure 11 This is a schematic diagram illustrating an example of a spin-flow magnetization reversal element according to one embodiment of the present invention. Figure 11 (a) is a top view. Figure 11 (b) is used Figure 11 (a) is a cross-sectional view obtained by cutting the center line of the width direction of the spin-orbit torque wiring 2, i.e., the XX line.

[0197] One embodiment of the present invention is a spin current magnetization reversal element, namely Figure 1 The spin current magnetization reversal element 101 shown includes: a second ferromagnetic metal layer 1 with variable magnetization direction, and a spin orbit torque wiring 2 extending along a second direction (x direction) that intersects the first direction (z direction) relative to the normal direction of the second ferromagnetic metal layer 1 and is engaged with the first surface 1a of the second ferromagnetic metal layer 1.

[0198] Here, the connection between the spin-orbit torque wiring 2 and the second ferromagnetic metal layer 1 can be "directly" connected, or as described above, connected via "other layers" such as a cover layer. If the structure is a structure in which a pure spin flow generated by the spin-orbit torque wiring 2 flows into the second ferromagnetic metal layer 1, then the connection (joining or coupling) between the spin-orbit torque wiring and the first ferromagnetic metal layer is not limited.

[0199] like Figure 12 As shown, the spin-orbit torque wiring 2 can be made into the following structure: a pure spin flow generating section 2A made of a material that generates pure spin flow, and a low resistance section 2B made of a material with a resistance less than that of the pure spin flow generating section. At least a portion of the pure spin flow generating section is in contact with the second ferromagnetic metal layer 1.

[0200] Figure 12 The structure shown is to Figure 3 The illustrated spin-orbit torque wiring structure is applied to an example of the spin-current magnetization reversal element of the present invention. It can be applied to the spin-current magnetization reversal element of the present invention. Figures 4-6 The structure of the spin-orbit torque wiring is shown.

[0201] As an example of the application of the spin current magnetization reversal element of the present invention, a magnetoresistive effect element can be mainly cited. Therefore, in the constituent elements of the spin current magnetization reversal element of the present invention, elements equivalent to the aforementioned magnetoresistive effect element and other constituent elements can be used.

[0202] Furthermore, the application of the spin-current magnetization reversal element of the present invention is not limited to magnetoresistive elements, and can also be applied to other applications. For example, it can be used in spatial light modulators where the spin-current magnetization reversal element is disposed in each pixel to spatially modulate incident light using a magneto-optical effect. In magnetic sensors, to avoid hysteresis effects based on the coercivity of the magnet, the magnetic field applied to the easy magnetization axis of the magnet can be replaced with the spin-current magnetization reversal element.

Claims

1. A magnetoresistive effect unit, comprising: A magnetoresistive element comprising a first ferromagnetic metal layer with a fixed magnetization direction, a second ferromagnetic metal layer with a variable magnetization direction, and a nonmagnetic layer sandwiched between the first and second ferromagnetic metal layers; and The spin-orbit torque wiring extends in a direction intersecting the stacking direction relative to the magnetoresistive effect element and is bonded to the second ferromagnetic metal layer. A covering layer is provided between the spin-orbit torque wiring and the second ferromagnetic metal layer. The spin-orbit torque wiring and the second ferromagnetic metal layer are joined together via the capping layer. The spin-orbit torque wiring is composed of non-magnetic heavy metals and magnetic metals. The coating layer uses any one of silver, copper, magnesium, and aluminum. The thickness of the capping layer is below the spin diffusion length of the material constituting the capping layer. The spin-orbit torque wiring has a sidewall joint that engages with the sidewall of the second ferromagnetic metal layer.

2. A magnetoresistive effect unit, comprising: A magnetoresistive element comprising a first ferromagnetic metal layer with a fixed magnetization direction, a second ferromagnetic metal layer with a variable magnetization direction, and a nonmagnetic layer sandwiched between the first and second ferromagnetic metal layers; and The spin-orbit torque wiring extends in a direction intersecting the stacking direction relative to the magnetoresistive effect element and is bonded to the second ferromagnetic metal layer. The spin-orbit torque wiring contains an antiferromagnetic metal. The antiferromagnetic metal is selected from one or more of IrMn and PtMn. The second ferromagnetic metal layer is composed of ferromagnetic material. The spin-orbit torque wiring has a first joint portion that engages with a first surface of the second ferromagnetic metal layer, and a sidewall joint portion that engages with a sidewall perpendicular to the first surface of the second ferromagnetic metal layer.

3. A magnetoresistive effect unit, comprising: A magnetoresistive element comprising a first ferromagnetic metal layer with a fixed magnetization direction, a second ferromagnetic metal layer with a variable magnetization direction, and a nonmagnetic layer sandwiched between the first and second ferromagnetic metal layers; and The spin-orbit torque wiring extends in a direction intersecting the stacking direction relative to the magnetoresistive effect element and is bonded to the second ferromagnetic metal layer. The spin-orbit torque wiring has a first joint portion that engages with a first surface of the second ferromagnetic metal layer, and a sidewall joint portion that engages with a sidewall perpendicular to the first surface of the second ferromagnetic metal layer. The second ferromagnetic metal layer is made of ferromagnetic material, and the spin-orbit torque wiring contains non-magnetic heavy metals.

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