Spin current magnetization reversal element, magnetoresistive element, magnetic memory, and magnetization reversal method

Abstract

To provide a spin current magnetization reversal element which utilizes magnetization reversal due to a pure spin current.SOLUTION: A spin current magnetization reversal element 101 comprises: a second ferromagnetic metal layer in which a direction of magnetization is variable; and a spin orbit torque wire extending in a direction across a perpendicular direction of the second ferromagnetic metal layer and joined to the second ferromagnetic metal layer. A cap layer is provided between the spin orbit torque wire and the second ferromagnetic metal layer. The spin orbit torque wire and the second ferromagnetic metal layer are joined via the cap layer, a spin current flows from the spin orbit torque wire through the cap layer to the second ferromagnetic metal layer, and the cap layer is composed of a material selected from the group consisting of Ru, Ta, Cu, Ag, Au, Mg and Al.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to a spin current magnetization reversal element, a magnetoresistive effect element, a magnetic memory, and a magnetization reversal method.

Background Art

[0002] A giant magnetoresistive (GMR) element composed of a multilayer film of a ferromagnetic layer and a nonmagnetic layer and a tunnel magnetoresistive (TMR) element using an insulating layer (tunnel barrier layer, barrier layer) as the nonmagnetic layer are known. Generally, although the element resistance of a TMR element is higher than that of a GMR element, the magnetoresistance (MR) ratio of a TMR element is larger than the MR ratio of a GMR element. Therefore, attention has been focused on TMR elements as elements for magnetic sensors, high-frequency components, magnetic heads, and nonvolatile random access memories (MRAMs).

[0003] As a writing method for MRAM, a method of performing writing (magnetization reversal) using a magnetic field generated by a current and a method of performing writing (magnetization reversal) using a spin transfer torque (STT) generated by flowing a current in the stacking direction of a magnetoresistive element are known. In the method using a magnetic field, when the element size becomes small, there is a problem that writing cannot be performed with a current that can flow through a thin wiring. On the other hand, in the method using a spin transfer torque (STT), one ferromagnetic layer (fixed layer, reference layer) spin-polarizes a current, and the spin of the current is transferred to the magnetization of the other ferromagnetic layer (free layer, recording layer), and writing (magnetization reversal) is performed by the torque (STT) generated at that time. However, there is an advantage that the current required for writing becomes smaller as the element size becomes smaller.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] From the perspective of energy efficiency, the magnetization reversal of a TMR element using STT is efficient, but the reversal current density for causing magnetization reversal is high. From the perspective of the long lifetime of the TMR element, it is desirable that this reversal current density be low. This also applies to GMR elements. Therefore, in any of the magnetic resistance effect elements such as TMR elements and GMR elements, it is desired to reduce the current density flowing through this magnetic resistance effect element.

[0006] In recent years, it has been proposed that magnetization reversal using a pure spin current generated by spin-orbit interaction is also applicable in practice (for example, Non-Patent Document 1). The pure spin current generated by spin-orbit interaction induces a spin-orbit torque (SOT), and magnetization reversal can occur depending on the magnitude of the SOT. The pure spin current is generated by having the same number of electrons with upward spins and electrons with downward spins flowing in opposite directions to each other, and since the flow of charge is canceled out, it is zero as the current flowing through the magnetic resistance effect element. If magnetization reversal can be achieved only with this pure spin current, since the current is zero, the long lifetime of the magnetic resistance effect element can be achieved. Alternatively, if STT is also used for magnetization reversal and SOT by a pure spin current can be used, the current used for STT can be reduced by the amount of SOT by a pure spin current, and it is considered that the long lifetime of the magnetic resistance effect element can be achieved. Even when both STT and SOT are used, it is considered that the higher the ratio of SOT used, the more the long lifetime of the magnetic resistance effect element can be achieved.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide a spin current magnetization reversal element, a magnetoresistive effect element, and a magnetic memory that utilize magnetization reversal by a pure spin current. Another object is to provide a magnetization reversal method for performing magnetization reversal of a magnetoresistive effect element using a pure spin current.

Means for Solving the Problems

[0008] In order to solve the above problems, the present invention provides the following means.

[0009] (1) A magnetoresistive effect element according to an aspect of the present invention includes a first ferromagnetic metal layer with a fixed magnetization direction, a second ferromagnetic metal layer with a variable magnetization direction, and a non-magnetic layer sandwiched between the first ferromagnetic metal layer and the second ferromagnetic metal layer. The magnetoresistive effect element is provided with a spin-orbit torque wiring that extends in a direction intersecting the stacking direction of the magnetoresistive effect element and is joined to the second ferromagnetic metal layer. At a portion where the magnetoresistive effect element and the spin-orbit torque wiring are joined, the current flowing through the magnetoresistive effect element and the current flowing through the spin-orbit torque wiring merge or are distributed.

[0010] (2) In the magnetoresistive effect element according to (1) above, the spin-orbit torque wiring may include a non-magnetic metal with an atomic number of 39 or more having d electrons or f electrons in the outermost shell.

[0011] (3) In the magnetoresistive effect element according to any one of (1) or (2) above, the spin-orbit torque wiring includes a pure spin current generation portion made of a material that generates a pure spin current and a low resistance portion made of a material having a lower electrical resistance than the pure spin current generation portion. At least a part of the pure spin current generation portion may be in contact with the second ferromagnetic metal layer.

[0012] (4) In the magnetoresistive effect element according to any one of (1) to (3) above, the spin-orbit torque wiring may include a magnetic metal.

[0013] (5) In the magnetoresistive effect element according to any one of (1) to (4) above, a cap layer is 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 cap layer.

[0014] (6) In the magnetoresistive effect element according to any one of (1) to (5) above, the spin-orbit torque wiring may have a sidewall junction portion that joins to the sidewall of the second ferromagnetic metal layer.

[0015] (7) A magnetic memory according to one aspect of the present invention includes a plurality of magnetoresistive effect elements according to any one of (1) to (6) above.

[0016] (8) A magnetization reversal method according to one aspect of the present invention is a method for reversing magnetization in the magnetoresistive effect element according to any one of (1) to (6) above, wherein the current density flowing through the spin-orbit torque wiring is less than 1×10 7 A / cm 2 and less.

[0017] (9) A magnetization reversal method according to one aspect of the present invention is a method for reversing magnetization in the magnetoresistive effect element according to any one of (1) to (6) above, wherein after a current is applied to the power supply of the spin-orbit torque wiring, a current is applied to the power supply of the magnetoresistive effect element.

[0018] (10) A spin current magnetization reversal element according to one aspect of the present invention includes a second ferromagnetic metal layer whose magnetization direction is variable, and a spin-orbit torque wiring that extends in a direction intersecting the plane normal direction of the second ferromagnetic metal layer and is joined to the second ferromagnetic metal layer. The spin-orbit torque wiring includes a pure spin current generation portion made of a material that generates a pure spin current, and a low resistance portion made of a material having a lower electrical resistance than the pure spin current generation portion, and at least a part of the pure spin current generation portion is in contact with the second ferromagnetic metal layer.

Advantages of the Invention

[0019] According to the magnetoresistive effect element of the present invention, the reversal current density flowing through the magnetoresistive effect element can be reduced.

Brief Description of the Drawings

[0020]

Figure 1

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Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0021] Hereinafter, the present invention will be described in detail with appropriate reference to the drawings. The drawings used in the following description may show, for the sake of convenience, the characteristic parts enlarged in order to make the characteristics of the present invention easier to understand, and the dimensional ratios of each component may be different from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto, and it can be appropriately modified and implemented within the scope where the effects of the present invention can be achieved.

[0022] (Magnetoresistive effect element) FIG. 1 is a perspective view schematically showing a magnetoresistive effect element according to one aspect of the present invention. A magnetoresistive effect element 100 according to one aspect of the present invention includes a magnetoresistive effect element 20 and a spin-orbit torque wiring 40 that extends in a direction intersecting the stacking direction of the magnetoresistive effect element 20 and is joined to the magnetoresistive effect element 20. Hereinafter, including FIG. 1, as an example of a configuration in which the spin-orbit torque wiring extends in a direction intersecting the stacking direction of the magnetoresistive effect element, the case of a configuration extending in an orthogonal direction will be described. In FIG. 1, a wiring 30 for flowing a current in the stacking direction of the magnetoresistive effect element 20, a substrate 10 on which the wiring 30 is formed, and a cap layer are also shown. Hereinafter, the stacking direction of the magnetoresistive effect element 20 is defined as the z direction, the direction perpendicular to the z direction and parallel to the spin-orbit torque wiring 40 is defined as the x direction, and the direction orthogonal to the x direction and the z direction is defined as the y direction.

[0023] <Magnetoresistive effect element> The magnetoresistive effect element 20 includes a first ferromagnetic metal layer 21 with a fixed magnetization direction, a second ferromagnetic metal layer 23 with a variable magnetization direction, and a non-magnetic layer 22 sandwiched between the first ferromagnetic metal layer 21 and the second ferromagnetic metal layer 23. The magnetization of the first ferromagnetic metal layer 21 is fixed in one direction, and by the relative change in the direction of magnetization of the second ferromagnetic metal layer 23, it functions as a magnetoresistive element 20. When applied to a coercivity difference type (pseudo spin valve type; Pseudo spin valve type) MRAM, the coercivity of the first ferromagnetic metal layer is greater than that of the second ferromagnetic metal layer. Also, when applied to an exchange bias type (spin valve; spin valve type) MRAM, in the first ferromagnetic metal layer, the direction of magnetization is fixed by exchange coupling with an antiferromagnetic layer. Also, when the non-magnetic layer 22 of the magnetoresistive element 20 is made of an insulator, it is a tunneling magnetoresistance (TMR) element, and when the non-magnetic layer 22 is made of a metal, it is a giant magnetoresistance (GMR) element.

[0024] As the magnetoresistive element provided by the present invention, the configuration of a known magnetoresistive element can be used. For example, each layer may be composed of a plurality of layers, or may include other layers such as an antiferromagnetic layer for fixing the direction of magnetization of the first ferromagnetic metal layer. The first ferromagnetic metal layer 21 is called a fixed layer or a reference layer, and the second ferromagnetic metal layer 23 is called a free layer or a memory layer, etc.

[0025] The first ferromagnetic metal layer 21 and the second ferromagnetic metal layer 23 may be either in-plane magnetization films in which the magnetization direction is in the in-plane direction parallel to the layer or perpendicular magnetization films in which the magnetization direction is perpendicular to the layer.

[0026] Known materials can be used for the material of the first ferromagnetic metal layer 21. For example, metals selected from the group consisting of Cr, Mn, Co, Fe, and Ni and alloys containing one or more of these metals and exhibiting ferromagnetism can be used. Also, alloys containing these metals and at least one element of B, C, and N can be used. Specifically, Co-Fe and Co-Fe-B can be mentioned.

[0027] In order to obtain higher output, it is preferable to use a Heusler alloy such as Co2FeSi. The Heusler alloy contains an intermetallic compound having a chemical composition of X2YZ, where X is a transition metal element or a noble metal element of the Co, Fe, Ni, or Cu group in the periodic table, Y is a transition metal of the Mn, V, Cr, or Ti group and can take the element type of X, and Z is a typical element from Group III to Group V. For example, Co2FeSi, Co2MnSi, Co2Mn 1-a Fe a Al b Si 1-b and the like can be mentioned.

[0028] In addition, in order to make the coercive force of the first ferromagnetic metal layer 21 with respect to the second ferromagnetic metal layer 23 larger, an antiferromagnetic material such as IrMn or PtMn may be used as the material in contact with the first ferromagnetic metal layer 21. Furthermore, in order 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 may be used.

[0029] Furthermore, when making the magnetization direction of the first ferromagnetic metal layer 21 perpendicular to the lamination plane, it is preferable to use a laminated film of Co and Pt. Specifically, the first ferromagnetic metal layer 21 can be [Co(0.24nm) / Pt(0.16nm)]6 / Ru(0.9nm) / [Pt(0.16nm) / Co(0.16nm)]4 / Ta(0.2nm) / FeB(1.0nm).

[0030] As the material of the second ferromagnetic metal layer 23, a ferromagnetic material, particularly a soft magnetic material, can be applied. For example, a metal selected from the group consisting of Cr, Mn, Co, Fe, and Ni, an alloy containing one or more of these metals, an alloy containing at least one of these metals and at least one element of B, C, and N, etc. can be used. Specifically, Co-Fe, Co-Fe-B, Ni-Fe can be mentioned.

[0031] When the magnetization direction of the second ferromagnetic metal layer 23 is perpendicular to the lamination plane, it is preferable that the thickness of the second ferromagnetic metal layer be 2.5 nm or less. Perpendicular magnetic anisotropy can be added to the second ferromagnetic metal layer 23 at the interface between the second ferromagnetic metal layer 23 and the nonmagnetic layer 22. Also, since the effect of perpendicular magnetic anisotropy attenuates as the film thickness of the second ferromagnetic metal layer 23 increases, it is preferable that the film thickness of the second ferromagnetic metal layer 23 be thin.

[0032] Known materials can be used for the nonmagnetic layer 22. For example, when the nonmagnetic layer 22 is made of an insulator (when it is a tunnel barrier layer), materials such as Al2O3, SiO2, MgO, and MgAl2O4 can be used as the material. Also, in addition to these, materials in which part of Al, Si, and Mg is replaced by Zn, Be, etc. can also be used. Among these, MgO and MgAl2O4 are materials in which coherent tunneling can be realized, so spin can be efficiently injected. Also, when the nonmagnetic layer 22 is made of a metal, materials such as Cu, Au, and Ag can be used as the material.

[0033] Also, as shown in FIG. 1, it is preferable that a cap layer 24 be formed on the surface of the second ferromagnetic metal layer 23 opposite to the nonmagnetic layer 22. The cap layer 24 can suppress the diffusion of elements from the second ferromagnetic metal layer 23. Also, the cap layer 24 contributes to the crystal orientation of each layer of the magnetoresistive effect element 20. As a result, by providing the cap 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 magnetoresistive effect element 20 can be made to have a lower resistance.

[0034] It is preferable to use a material with high conductivity for the cap layer 24. For example, Ru, Ta, Cu, Ag, Au, etc. can be used. The crystal structure of the cap layer 24 is preferably set appropriately from an fcc structure, an hcp structure, or a bcc structure according to the crystal structure of the adjacent ferromagnetic metal layer.

[0035] In addition, it is preferable to use any one selected from the group consisting of silver, copper, magnesium, and aluminum for the cap layer 24. Although details will be described later, when the spin orbit torque wiring 40 and the magnetoresistive element 20 are connected via the cap layer 24, it is preferable that the cap layer 24 does not dissipate the spin propagated from the spin orbit torque wiring 40. Silver, copper, magnesium, aluminum, etc. are known to have a long spin diffusion length of 100 nm or more and are difficult for spins to dissipate.

[0036] The thickness of the cap layer 24 is preferably equal to or less than the spin diffusion length of the material constituting the cap layer 24. If the thickness of the cap layer 24 is equal to or less than the spin diffusion length, the spin propagated from the spin orbit torque wiring 40 can be sufficiently transmitted to the magnetoresistive element 20.

[0037] <Spin Orbit Torque Wiring> The spin orbit torque wiring extends in a direction intersecting the stacking direction of the magnetoresistive element. The spin orbit torque wiring is electrically connected to a power source that passes an electric current in a direction orthogonal to the stacking direction of the magnetoresistive element in the spin orbit torque wiring, and functions as a spin injection means for injecting a pure spin current into the magnetoresistive element together with the power source. The spin orbit torque wiring 40 may be directly connected to the second ferromagnetic metal layer 23, or may be connected via another layer, for example, via the cap layer 24 as shown in FIG. 1.

[0038] The spin orbit torque wiring is made of a material in which a pure spin current is generated by the spin Hall effect when an electric current flows. Such a material only needs to have a configuration in which a pure spin current is generated in the spin orbit torque wiring. Therefore, it is not limited to a material composed of a single element, and may be composed of a portion composed of a material in which a pure spin current is generated and a portion composed of a material in which a pure spin current is not generated. The spin Hall effect is a phenomenon in which a pure spin current is induced in a direction orthogonal to the direction of an electric current based on the spin orbit interaction when an electric current is passed through a material.

[0039] Figure 2 is a schematic diagram for explaining the spin Hall effect. Based on Figure 2, the mechanism by which a pure spin current is generated by the spin Hall effect will be explained.

[0040] As shown in Figure 2, when a current I is passed in the extending direction of the spin-orbit torque wiring 40, the upward spin S + (S1) and the downward spin S - (S2) are each bent in a direction perpendicular to the current. The ordinary Hall effect and the spin Hall effect are common in that the moving charges (electrons) are bent in the moving direction. However, in the ordinary Hall effect, charged particles moving in a magnetic field are bent in the moving direction by the Lorentz force, while in the spin Hall effect, the moving direction is bent only by the movement of electrons (only when a current flows) without the presence of a magnetic field, which is a significant difference. In a non-magnetic material (a material that is not a ferromagnetic material), the number of electrons with upward spin S + is equal to the number of electrons with downward spin S - . Therefore, in the figure, the number of electrons with upward spin S + moving upward is equal to the number of electrons with downward spin S - moving downward. As a result, the net flow of charge, that is, the current, is zero. This spin current without this current is particularly called a pure spin current. On the other hand, when a current is passed through a ferromagnetic material, the upward spin electrons and the downward spin electrons are bent in opposite directions in the same way. However, in a ferromagnetic material, since either the upward spin electrons or the downward spin electrons are in a state where there are more of them, as a result, a net flow of charge occurs (a voltage is generated), which is different. Therefore, as a material for the spin-orbit torque wiring, a material composed only of a ferromagnetic material is not included.

[0041] Here, if the flow of electrons with upward spin S + is represented as J ↑ , the flow of electrons with downward spin S - is represented as J ↓ , and the spin current is represented as J S , then J S = J ↑ - J ↓It is defined as follows. In FIG. 2, the pure spin current J S flows upward in the figure. Here, J S is a flow of electrons with a polarization rate of 100%. In FIG. 2, when a ferromagnetic material is brought into contact with the upper surface of the spin-orbit torque wiring 40, the pure spin current diffuses into the ferromagnetic material and flows in. In the present invention, a pure spin current is generated by flowing a current through the spin-orbit torque wiring in this way, and the pure spin current diffuses into the second ferromagnetic metal layer in contact with the spin-orbit torque wiring. Thus, it can be used as an assisting means or a main means for magnetization reversal of the ferromagnetic metal layer in a magnetoresistive element using the conventional STT, or can also be used in a novel magnetoresistive element that performs magnetization reversal of the ferromagnetic metal layer only by SOT due to the pure spin current.

[0042] As methods for assisting magnetization reversal, a method of applying an external magnetic field, a method of applying a voltage, a method of applying heat, and a method of utilizing strain of a substance are known. However, in the case of the method of applying an external magnetic field, the method of applying a voltage, and the method of applying heat, it is necessary to newly provide external wirings, heat sources, etc., and the element configuration becomes complicated. Also, in the case of the method of utilizing strain of a substance, it is difficult to control the once-generated strain during the usage mode, and magnetization reversal cannot be performed with good controllability.

[0043] The spin-orbit torque wiring 40 may contain a nonmagnetic heavy metal. Here, the heavy metal is used in the sense of a metal having a specific gravity of yttrium or more. The spin-orbit torque wiring 40 may be composed only of a nonmagnetic heavy metal. In this case, the nonmagnetic heavy metal is preferably a nonmagnetic metal with a large atomic number of 39 or more having d electrons or f electrons in the outermost shell. This is because such a nonmagnetic metal has a large spin-orbit interaction that causes the spin Hall effect. The spin-orbit torque wiring 40 may be composed only of a nonmagnetic heavy metal with a large atomic number of 39 or more having d electrons or f electrons in the outermost shell. Generally, when an electric current flows through a metal, all electrons move in the direction opposite to the current regardless of the direction of their spins. In contrast, in a nonmagnetic metal with a large atomic number having d or f electrons in its outermost shell, due to the large spin-orbit interaction, the direction of electron movement depends on the direction of the electron spin due to the spin Hall effect, and a pure spin current JS is likely to be generated.

[0044] In addition, the spin-orbit torque wiring 40 may include a magnetic metal. The magnetic metal refers to a ferromagnetic metal or an antiferromagnetic metal. When a trace amount of a magnetic metal is included in a nonmagnetic metal, the spin-orbit interaction is enhanced, and the spin current generation efficiency with respect to the current flowing through the spin-orbit torque wiring 40 can be increased. The spin-orbit torque wiring 40 may be composed only of an antiferromagnetic metal. Since the spin-orbit interaction is caused by the intrinsic internal field of the substance of the spin-orbit torque wiring material, a pure spin current is generated even in a nonmagnetic material. When a trace amount of a magnetic metal is added to the spin-orbit torque wiring material, the spin current generation efficiency is improved because the magnetic metal itself scatters the electron spins flowing through it. However, if the amount of the added magnetic metal increases too much, the generated pure spin current is scattered by the added magnetic metal, and as a result, the effect of reducing the spin current becomes stronger. Therefore, the molar ratio of the added magnetic metal is preferably sufficiently smaller than the molar ratio of the main component of the pure spin generation part in the spin-orbit torque wiring. Speaking of a guideline, the molar ratio of the added magnetic metal is preferably 3% or less.

[0045] In addition, the spin-orbit torque wiring 40 may include a topological insulator. The spin-orbit torque wiring 40 may be composed only of a topological insulator. A topological insulator is a substance in which the interior of the substance is an insulator or a high-resistance body, but a spin-polarized metallic state is generated on its surface. There is something like an internal magnetic field called spin-orbit interaction in the substance. Therefore, even without an external magnetic field, a new topological phase appears due to the effect of the spin-orbit interaction. This is a topological insulator, and a pure spin current can be generated with high efficiency due to the strong spin-orbit interaction and the breaking of the time-reversal symmetry at the edge. Examples of topological insulators include SnTe, Bi1.5 Sb 0.5 Te 1.7 Se 1.3 , TlBiSe2, Bi2Te3, (Bi 1-x Sb x )2Te3 etc. are preferable. These topological insulators can generate spin current with high efficiency.

[0046] <Substrate> The substrate 10 preferably has excellent flatness. In order to obtain a surface with excellent flatness, for example, Si, AlTiC, etc. can be used as the material.

[0047] On the surface of the substrate 10 on the side of the magnetoresistive element 20, an underlayer (not shown) may be formed. When the underlayer is provided, the crystallinity such as the crystal orientation and crystal grain size of each layer including the first ferromagnetic metal layer 21 laminated on the substrate 10 can be controlled.

[0048] The underlayer preferably has insulating properties. This is to prevent the current flowing through the wiring 30 etc. from dissipating. Various materials can be used for the underlayer. For example, as one example, a nitride layer having a (001)-oriented NaCl structure and containing at least one element selected from the group of Ti, Zr, Nb, V, Hf, Ta, Mo, W, B, Al, Ce can be used for the underlayer.

[0049] As another example, a (002)-oriented perovskite-based conductive oxide layer represented by the composition formula of ABO3 can be used for the underlayer. Here, site A contains at least one element selected from the group of Sr, Ce, Dy, La, K, Ca, Na, Pb, Ba, and site B contains at least one element selected from the group of Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Nb, Mo, Ru, Ir, Ta, Ce, Pb.

[0050] As another example, an oxide layer having a (001)-oriented NaCl structure and containing at least one element selected from the group of Mg, Al, Ce can be used for the underlayer.

[0051] As another example, a layer having a tetragonal or cubic crystal structure oriented in (001) and containing at least one element selected from the group consisting of Al, Cr, Fe, Co, Rh, Pd, Ag, Ir, Pt, Au, Mo, and W can be used as the underlayer.

[0052] Also, the underlayer is not limited to a single layer, and a plurality of layers of the layers in the above examples may be stacked. By devising the configuration of the underlayer, the crystallinity of each layer of the magnetic resistance effect element 20 can be enhanced, and the magnetic properties can be improved.

[0053] <Wiring> The wiring 30 is electrically connected to the first ferromagnetic metal layer 21 of the magnetic resistance effect element 20. In FIG. 1, the wiring 30, the spin-orbit torque wiring 40, and a power source (not shown) form a closed circuit, and a current flows in the stacking direction of the magnetic resistance effect element 20.

[0054] The wiring 30 is not particularly limited as long as it is a material with high conductivity. For example, aluminum, silver, copper, gold, etc. can be used.

[0055] FIGS. 3 to 6 are schematic diagrams for explaining embodiments of the spin-orbit torque wiring. Each of (a) is a cross-sectional view and (b) is a plan view.

[0056] In the magnetic resistance effect element of the present invention, even in a configuration in which the magnetization reversal of the magnetic resistance effect element is performed only by the SOT by a pure spin current (hereinafter sometimes referred to as the "SOT-only" configuration), or in a configuration in which the SOT by a pure spin current is used in combination with the conventional magnetic resistance effect element using STT (hereinafter sometimes referred to as the "STT and SOT combined" configuration), the current flowing through the spin-orbit torque wiring (hereinafter sometimes referred to as the "SOT reversal current") is a normal current accompanied by a flow of charges, and thus Joule heat is generated when a current flows. The embodiments of the spin-orbit torque wiring shown in FIGS. 3 to 6 are examples of configurations that reduce the Joule heat due to the SOT reversal current by a configuration other than the above materials.

[0057] In the "combined use of STT and SOT" configuration, the current flowing for magnetization reversal of the magnetoresistive element of the present invention includes, in addition to the current directly flowing through the magnetoresistive element to utilize the STT effect (hereinafter sometimes referred to as the "STT reversal current"), the current flowing through the spin-orbit torque wiring to utilize the SOT effect ("SOT reversal current"). Since both currents are ordinary currents accompanied by the flow of charge, Joule heat is generated when the current flows. In this configuration, in order to combine magnetization reversal by the STT effect and magnetization reversal by the SOT effect, the STT reversal current is reduced compared to the configuration in which magnetization reversal is performed only by the STT effect, but energy corresponding to the SOT reversal current is consumed.

[0058] Heavy metals, which are materials capable of generating a pure spin current, have a higher electrical resistance than the metals used as ordinary wiring. Therefore, from the viewpoint of reducing Joule heat due to the SOT reversal current, it is preferable that the spin-orbit torque wiring has a portion with a lower electrical resistance rather than being entirely composed of only materials capable of generating a pure spin current. That is, from this viewpoint, the spin-orbit torque wiring preferably comprises a portion made of a material capable of generating a pure spin current (spin current generation portion) and a portion made of a material having a lower electrical resistance than this spin current generation portion (low resistance portion).

[0059] The spin current generation portion only needs to be made of a material capable of generating a pure spin current, and may be, for example, a configuration composed of a plurality of types of material portions. As the low resistance portion, materials used as ordinary wiring can be used. For example, aluminum, silver, copper, gold, etc. can be used. The low resistance portion only needs to be made of a material having a lower electrical resistance than the spin current generation portion, and may be, for example, a configuration composed of a plurality of types of material portions. Note that a pure spin current may be generated in the low-resistance portion. In this case, the distinction between the spin current generation portion and the low-resistance portion can be made such that a portion consisting of the materials described as those of the spin current generation portion and the low-resistance portion in this specification is the spin current generation portion or the low-resistance portion. Also, a portion other than the main portion that generates a pure spin current and having an electrical resistance smaller than that of the main portion can be distinguished as the low-resistance portion from the spin current generation portion.

[0060] The spin current generation portion may contain a non-magnetic heavy metal. In this case, it suffices to contain a finite amount of a heavy metal capable of generating a pure spin current. Further, in this case, the spin current generation portion is a concentration region where the heavy metal capable of generating a pure spin current is sufficiently less than the main component of the spin current generation portion, or the heavy metal capable of generating a pure spin current is preferably the main component, for example, 90% or more. The heavy metal in this case is preferably 100% of a non-magnetic metal having an atomic number of 39 or more having d electrons or f electrons in the outermost shell and capable of generating a pure spin current. Here, the concentration range where the heavy metal capable of generating a pure spin current is sufficiently less than the main component of the spin current generation section means, for example, in the spin current generation section mainly composed of copper, the concentration of the heavy metal is 10% or less in terms of molar ratio. When the main component constituting the spin current generation section is other than the above-mentioned heavy metal, the concentration of the heavy metal contained in the spin current generation section is preferably 50% or less, more preferably 10% or less in terms of molar ratio. These concentration ranges are regions where the effect of electron spin scattering can be effectively obtained. When the concentration of the heavy metal is low, the light metal having an atomic number smaller than that of the heavy metal becomes the main component. In this case, it is assumed that the heavy metal atoms are disorderly dispersed in the light metal, rather than forming an alloy with the light metal. Since the spin-orbit interaction is weak in the light metal, it is difficult to generate a pure spin current by the spin Hall effect. However, when electrons pass through the heavy metal in the light metal, the spin is scattered at the interface between the light metal and the heavy metal, so that a pure spin current can be efficiently generated even in a region where the concentration of the heavy metal is low. When the concentration of the heavy metal exceeds 50%, the ratio of the spin Hall effect in the heavy metal increases, but the effect of the interface between the light metal and the heavy metal decreases, so the overall effect decreases. Therefore, the concentration of the heavy metal at which a sufficient interface effect can be expected is preferable.

[0061] Further, when the above-mentioned spin-orbit torque wiring contains a magnetic metal, the spin current generation section in the spin-orbit torque wiring can be made of an antiferromagnetic metal. The antiferromagnetic metal can obtain the same effect as the case where the heavy metal has 100% of a non-magnetic metal with an atomic number of 39 or more having d electrons or f electrons in the outermost shell. As the antiferromagnetic metal, for example, IrMn and PtMn are preferable, and IrMn which is stable against heat is more preferable. Further, when the above-mentioned spin-orbit torque wiring contains a topological insulator, the spin current generation section in the spin-orbit torque wiring can be made of a topological insulator. Examples of the topological insulator include SnTe, Bi 1.5 Sb 0.5 Te 1.7 Se 1.3 ,TlBiSe2,Bi2Te3,(Bi 1-x Sb x)2Te3 and the like are preferable. These topological insulators can generate spin current with high efficiency.

[0062] In order for the pure spin current generated in the spin-orbit torque wiring to effectively diffuse into the magnetoresistive element, at least a part of the spin current generation part needs to be in contact with the second ferromagnetic metal layer. When a cap layer is provided, at least a part of the spin current generation part needs to be in contact with the cap layer. All of the embodiments of the spin-orbit torque wiring shown in FIGS. 3 to 6 have a configuration in which at least a part of the spin current generation part is in contact with the second ferromagnetic metal layer.

[0063] In the embodiment shown in FIG. 3, in the spin-orbit torque wiring 40, all of the joints 40' with the second ferromagnetic metal layer are composed of the spin current generation part 41, and the spin current generation part 41 is sandwiched between the low-resistance parts 42A and 42B.

[0064] Here, when the spin current generation part and the low-resistance part are arranged electrically in parallel, the current flowing through the spin-orbit torque wiring is divided in proportion to the inverse ratio of the resistances of the spin current generation part and the low-resistance part and flows through each part. From the viewpoint of the pure spin current generation efficiency with respect to the SOT inversion current, in order for the current flowing through the spin-orbit torque wiring to all flow through the spin current generation part, there is no part where the spin current generation part and the low-resistance part are arranged electrically in parallel, and all are arranged electrically in series. The spin-orbit torque wiring shown in FIGS. 3 to 6 has a configuration in which there is no part where the spin current generation part and the low-resistance part are arranged electrically in parallel in a plan view from the stacking direction of the magnetoresistive element, and it is the case of the configuration having the cross section shown in (a) and having the highest pure spin current generation efficiency with respect to the SOT inversion current.

[0065] The spin-orbit torque wiring 40 shown in FIG. 3 is configured such that its spin current generation part 41 overlaps so as to include the joint part 23' of the second ferromagnetic metal layer 23 when viewed in plan from the stacking direction of the magnetoresistive effect element 20, and its thickness direction consists only of the spin current generation part 41, and low-resistance parts 42A and 42B are arranged so as to sandwich the spin current generation part 41 in the direction of current flow. As a modified example of the spin-orbit torque wiring shown in FIG. 3, there is a configuration in which the spin current generation part overlaps so as to overlap the joint part of the second ferromagnetic metal layer when viewed in plan from the stacking direction of the magnetoresistive effect element, and the rest is the same as the spin-orbit torque wiring shown in FIG. 3.

[0066] The spin-orbit torque wiring 40 shown in FIG. 4 is configured such that its spin current generation part 41 overlaps a part of the joint part 23' of the second ferromagnetic metal layer 23 when viewed in plan from the stacking direction of the magnetoresistive effect element 20, and its thickness direction consists only of the spin current generation part 41, and low-resistance parts 42A and 42B are arranged so as to sandwich the spin current generation part 41 in the direction of current flow.

[0067] The spin-orbit torque wiring 40 shown in FIG. 5 is configured such that its spin current generation part 41 overlaps so as to include the joint part 23' of the second ferromagnetic metal layer 23 when viewed in plan from the stacking direction of the magnetoresistive effect element 20, and in its thickness direction, the spin current generation part 41 and the low-resistance part 42C are stacked in order from the second ferromagnetic metal layer side, and low-resistance parts 42A and 42B are arranged so as to sandwich the part where the spin current generation part 41 and the low-resistance part 42C are stacked in the direction of current flow. As a modified example of the spin-orbit torque wiring shown in FIG. 5, there is a configuration in which the spin current generation part overlaps so as to overlap the joint part of the second ferromagnetic metal layer when viewed in plan from the stacking direction of the magnetoresistive effect element, and the rest is the same as the spin-orbit torque wiring shown in FIG. 5.

[0068] The spin-orbit torque wiring 40 shown in FIG. 6 includes a first spin current generation part 41A in which a spin current generation part 41 is formed over the entire surface on the side of the second ferromagnetic metal layer, a second spin current generation part 41B which is laminated on the first spin current generation part and overlaps so as to include a junction part 23' of the second ferromagnetic metal layer 23 when viewed in plan from the lamination direction of the magnetoresistive effect element 20, and the thickness direction of which consists only of the spin current generation part, and low-resistance parts 42A and 42B which are arranged so as to sandwich the second spin current generation part 41B in the direction of current flow. As a modified example of the spin-orbit torque wiring shown in FIG. 6, there is a configuration in which the second spin current generation part overlaps so as to overlap the junction part of the second ferromagnetic metal layer when viewed in plan from the lamination direction of the magnetoresistive effect element, and the rest is the same as the spin-orbit torque wiring shown in FIG. 6. In the configuration shown in FIG. 6, since the area where the spin current generation part 41 and the low-resistance part 42 are in contact is large, the adhesion between the nonmagnetic metal with a large atomic number constituting the spin current generation part 41 and the metal constituting the low-resistance part 42 is high.

[0069] The magnetoresistive effect element of the present invention can be manufactured using a known method. Hereinafter, the manufacturing method of the magnetoresistive effect element illustrated in FIGS. 3 to 6 will be described. First, the magnetoresistive effect element 20, for example, can be formed using a magnetron sputtering apparatus. When the magnetoresistive effect element 20 is a TMR element, for example, the tunnel barrier layer is first sputtered with a metal thin film of aluminum of about 0.4 to 2.0 nm and a divalent cation of a plurality of nonmagnetic elements on the first ferromagnetic metal layer, and plasma oxidation or natural oxidation by oxygen introduction is performed, and then formed by heat treatment. As the film formation method, in addition to the magnetron sputtering method, thin film formation methods such as an evaporation method, a laser ablation method, and an MBE method can be used. After forming the film and the shape of the magnetoresistive effect element 20, it is preferable to first form the spin current generation part 41. This leads to high efficiency because it makes the structure capable of suppressing the scattering of the pure spin current from the spin current generation part 41 to the magnetoresistive effect element 20 as much as possible. After forming the film and shaping the magnetoresistive effect element 20, the periphery of the processed magnetoresistive effect element 20 is filled with a resist or the like to form a surface including the upper surface of the magnetoresistive effect element 20. At this time, it is preferable to flatten the upper surface of the magnetoresistive effect element 20. By flattening, spin scattering at the interface between the spin current generation part 41 and the magnetoresistive effect element 20 can be suppressed. Next, a material for the spin current generation part 41 is formed on the flattened upper surface of the magnetoresistive effect element 20. For film formation, sputtering or the like can be used. Next, a resist or a protective film is installed on the part where the spin current generation part 41 is to be fabricated, and unnecessary parts are removed using the ion milling method or the reactive ion etching (RIE) method. Next, a material constituting the low-resistance part 42 is formed by sputtering or the like, and the resist or the like is peeled off, whereby the spin-orbit torque wiring 40 is fabricated. When the shape of the spin current generation part 41 is complicated, the formation of the resist or the protective film and the film formation of the spin current generation part 41 may be performed in multiple steps.

[0070] FIG. 7 is a schematic cross-sectional view of a magnetoresistive effect element according to one aspect of the present invention, cut in the yz plane. Based on FIG. 7, the operation of the magnetoresistive effect element 100 according to one aspect of the present invention will be described.

[0071] As shown in FIG. 7, there are two types of currents in the magnetoresistive effect element 100. One is the current I1 (STT inversion current) that flows through the magnetoresistive effect element 20 in its stacking direction and flows through the spin-orbit torque wiring 40 and the wiring 30. In FIG. 7, it is assumed that the current I1 flows in the order of the spin-orbit torque wiring 40, the magnetoresistive effect element 20, and the wiring 30. In this case, electrons flow in the order of the wiring 30, the magnetoresistive effect element 20, and the spin-orbit torque wiring 40. The other is the current I2 (SOT inversion current) that flows in the extending direction of the spin-orbit torque wiring 40. The current I1 and the current I2 intersect (are orthogonal) to each other. At the portion where the magnetoresistive effect element 20 and the spin-orbit torque wiring 40 are joined (reference numeral 24' indicates the joint portion on the magnetoresistive effect element 20 (cap layer 24) side, and reference numeral 40' indicates the joint portion on the spin-orbit torque wiring 40 side), the current flowing through the magnetoresistive effect element 20 and the current flowing through the spin-orbit torque wiring 40 merge or are distributed.

[0072] By flowing the current I1, electrons having spins in the same direction as the magnetization of the first ferromagnetic metal layer (fixed layer) 21 pass through the nonmagnetic layer 22 while maintaining the spin direction from the first ferromagnetic metal layer (fixed layer) 21, and these electrons 23 exert a torque (STT) so as to reverse and align the direction of the magnetization M 21 of the second ferromagnetic metal layer (free layer) 23 with respect to the direction of the magnetization M

[0073] On the other hand, the current I2 corresponds to the current I shown in FIG. 2. That is, when the current I2 is flowed, the upward spin S + and the downward spin S - are bent toward the ends of the spin-orbit torque wiring 40 respectively, and a pure spin current J s is generated. The pure spin current J s is induced in a direction perpendicular to the direction in which the current I2 flows. That is, a pure spin current J s is generated in the z-axis direction or the x-axis direction in the figure. In FIG. 7, only the pure spin current J s in the z-axis direction contributing to the direction of the magnetization of the second ferromagnetic metal layer 23 is illustrated.

[0074] The pure spin current J s generated by flowing the current I2 to the front side of the figure in the spin-orbit torque wiring 40 diffuses into and flows into the second ferromagnetic metal layer 23 through the cap layer 24, and the flowing-in spins affect the magnetization M 23 of the second ferromagnetic metal layer 23. That is, in FIG. 7, when spins directed in the -x direction flow into the second ferromagnetic metal layer 23, a torque (SOT) is applied that attempts to cause magnetization reversal of the magnetization M 23 of the second ferromagnetic metal layer 23 directed in the +x direction.

[0075] As described above, the pure spin current J generated by the current flowing through the second current path I2 is added to the STT effect generated by the current flowing through the first current path I1, s and the magnetization M23 of the second ferromagnetic metal layer 23 is reversed by the SOT effect caused by J.

[0076] If an attempt is made to reverse the magnetization of the second ferromagnetic metal layer 23 only by the STT effect (i.e., only current I1 flows), it is necessary to apply a voltage equal to or higher than a predetermined voltage to the magnetoresistive effect element 20. Although the general driving voltage of the TMR element is relatively small, on the order of several V or less, the non-magnetic layer 22 is a very thin film on the order of several nm, and dielectric breakdown may occur. By continuously energizing the non-magnetic layer 22, the weak parts of the non-magnetic layer (poor film quality, thin film thickness, etc.) are probabilistically destroyed.

[0077] On the other hand, in the case of the magnetoresistive effect element of the "combined use of STT and SOT" configuration of the present invention, in addition to the STT effect, the SOT effect is utilized. As a result, the voltage applied to the magnetoresistive effect element can be reduced, and the current density of the current flowing through the spin-orbit torque wiring can also be reduced. By reducing the voltage applied to the magnetoresistive effect element, the long life of the element can be achieved. Also, by reducing the current density of the current flowing through the spin-orbit torque wiring, it is possible to avoid a significant decrease in energy efficiency.

[0078] The current density of the current flowing through the spin-orbit torque wiring is 1×10 7 A / cm 2It is preferably less than. When the current density of the current flowing through the spin-orbit torque wiring is too large, heat is generated by the current flowing through the spin-orbit torque wiring. When heat is applied to the second ferromagnetic metal layer, the stability of the magnetization of the second ferromagnetic metal layer is lost, and unexpected magnetization reversal or the like may occur. When such unexpected magnetization reversal occurs, there is a problem that the recorded information is rewritten. That is, in order to avoid unexpected magnetization reversal, it is preferable that the current density of the current flowing through the spin-orbit torque wiring does not become too large. The current density of the current flowing through the spin-orbit torque wiring is 1×10 7 A / cm 2 If it is less than, at least the generated heat can be avoided from causing magnetization reversal.

[0079] FIG. 8 shows a magnetoresistive element according to another embodiment of the present invention. In the magnetoresistive element 200 shown in FIG. 8, the spin-orbit torque wiring 50 has, in addition to the upper surface junction portion 51 (corresponding to the spin-orbit torque wiring 40 described above) provided in the stacking direction of the magnetoresistive element 20, a side wall junction portion 52 joined to the side wall of the second ferromagnetic metal layer 23.

[0080] When a current is passed through the spin-orbit torque wiring 50, in addition to the pure spin current J s generated at the upper surface junction portion 51, a pure spin current J s ' is generated at the side wall junction portion 52. Therefore, not only does the pure spin current J s flow from the upper surface of the magnetoresistive element 20 through the cap layer 24 into the second ferromagnetic metal layer 23, but also the pure spin current J s ' flows in from the side wall of the second ferromagnetic metal layer 23, so the SOT effect is enhanced.

[0081] FIG. 9 shows a magnetoresistive element according to another embodiment of the present invention. In the magnetoresistive element 300 shown in FIG. 9, the 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 reversed from that of the magnetoresistive element 100 shown in FIG. 1. As described above, the magnetoresistive element of the present invention may have a top pin structure as in this configuration, or may have a bottom pin structure as shown in FIG. 1.

[0082] In the magnetoresistive element 300 shown in FIG. 9, a substrate 10, a spin orbit torque wiring 40, a second ferromagnetic metal layer 23, a nonmagnetic layer 22, a first ferromagnetic metal layer 21, a cap layer 24, and a wiring 30 are laminated in this order. Since the second ferromagnetic metal layer 23 is laminated before the first ferromagnetic metal layer 21, the possibility of being affected by lattice strain or the like is lower than that of the magnetoresistive element 100. As a result, in the magnetoresistive element 300, the perpendicular magnetic anisotropy of the second ferromagnetic metal layer 23 is enhanced. When the perpendicular magnetic anisotropy of the second ferromagnetic metal layer 23 increases, the MR ratio of the magnetoresistive element can be increased.

[0083] FIG. 10 shows a first power source 110 that passes a current in the stacking direction of the magnetoresistive element 20 and a second power source 120 that passes a current through the spin orbit torque wiring 40 in the magnetoresistive element 100 shown in FIG. 1.

[0084] The first power source 110 is connected to the wiring 30 and the spin orbit torque wiring 40. The first power source 110 can control the current flowing in the stacking direction of the magnetoresistive element 100. The second power source 120 is connected to both ends of the spin orbit torque wiring 40. The second power source 120 can control the current flowing through the spin orbit torque wiring 40, which is a current flowing in a direction orthogonal to the stacking direction of the magnetoresistive element 20.

[0085] As described above, the current flowing in the stacking direction of the magnetoresistive element 20 induces STT. On the other hand, 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.

[0086] In this way, by controlling the stacking direction of the magnetoresistive element 20 and the amount of current flowing in the direction perpendicular to this stacking direction by two power supplies, it is possible to freely control the contribution rates of SOT and STT to magnetization reversal.

[0087] For example, when a large current cannot flow through the device, it is possible to control so that STT, which has high energy efficiency for magnetization reversal, becomes dominant. That is, it is possible to increase the amount of current flowing from the first power supply 110 and decrease the amount of current flowing from the second power supply 120. Further, for example, when it is necessary to fabricate a thin device and the thickness of the nonmagnetic layer 22 has to be reduced, it is required to reduce the current flowing through the nonmagnetic layer 22. In this case, it is possible to decrease the amount of current flowing from the first power supply 110 and increase the amount of current flowing from the second power supply 120 to increase the contribution rate of SOT.

[0088] As the first power supply 110 and the second power supply 120, known ones can be used.

[0089] As described above, according to the magnetoresistive element according to one aspect of the present invention, the contribution rates of STT and SOT can be freely controlled by the amounts of current supplied from the first power supply and the second power supply. Therefore, according to the performance required for the device, the contribution rates of STT and SOT can be freely controlled, and it can function as a more versatile magnetoresistive element.

[0090] (Magnetic memory) The magnetic memory (MRAM) of the present invention includes a plurality of the magnetoresistive elements of the present invention.

[0091] (Magnetization reversal method) The magnetization reversal method according to one aspect of the present invention is such that, in the magnetoresistive element of the present invention, the current density flowing through the spin-orbit torque wiring is less than 1×10 7 A / cm 2 and less. If the current density of the current flowing through the spin-orbit torque wiring is too large, heat is generated by the current flowing through the spin-orbit torque wiring. When heat is applied to the second ferromagnetic metal layer, the stability of the magnetization of the second ferromagnetic metal layer is lost, and unexpected magnetization reversal or the like may occur. When such unexpected magnetization reversal occurs, there arises a problem that the recorded information is rewritten. That is, in order to avoid unexpected magnetization reversal, it is preferable that the current density of the current flowing through the spin-orbit torque wiring does not become too large. If the current density of the current flowing through the spin-orbit torque wiring is less than 1×10 7 A / cm 2 it is possible to at least avoid magnetization reversal due to the generated heat.

[0092] The magnetization reversal method according to one aspect of the present invention applies a current to the power supply of the spin-orbit torque wiring in the magnetoresistive element of the present invention, and then applies a current to the power supply of the magnetoresistive element. The assist process and the magnetization reversal process may be performed simultaneously, or the magnetization reversal process may be added after the assist process is performed in advance. That is, in the magnetoresistive element 200 shown in FIG. 7, currents may be simultaneously supplied from the first power supply 110 and the second power supply 120, or after a current is supplied from the second current 120, a current may be additionally supplied from the first power supply 110. However, in order to more surely obtain the assist effect of magnetization reversal using SOT, it is preferable to apply a current to the power supply of the magnetoresistive element after a current is applied to the power supply of the spin-orbit torque wiring. That is, it is preferable to additionally supply a current from the first power supply 110 after a current is supplied from the second current 120.

[0093] (Spin current magnetization reversal element) FIG. 11 shows a schematic diagram of an example of a spin current magnetization reversal element according to an embodiment of the present invention. FIG. 11(a) is a plan view, and FIG. 11(b) is a cross-sectional view taken along the X-X line which is the center line in the width direction of the spin-orbit torque wiring 2 in FIG. 11(a). The spin current magnetization reversal element according to one aspect of the present invention, the spin current magnetization reversal element 101 shown in FIG. 1, includes a second ferromagnetic metal layer 1 with a variable magnetization direction, and a first direction (z direction) which is the plane normal direction of the second ferromagnetic metal layer 1. It includes a spin-orbit torque wiring 2 extending in a second direction (x direction) intersecting with the first direction and joined to the first surface 1a of the second ferromagnetic metal layer 1. Here, the junction of the spin-orbit torque wiring 2 and the second ferromagnetic metal layer 1 may be "directly" joined, or may be joined "through another layer" such as a cap layer as described above. As long as the pure spin current generated in the spin-orbit torque wiring 2 flows into the second ferromagnetic metal layer 1, there is no limitation on the method of joining (connecting or coupling) the spin-orbit torque wiring and the first ferromagnetic metal layer.

[0094] As shown in FIG. 12, the spin-orbit torque wiring 2 is composed of a pure spin current generation part 2A made of a material that generates a pure spin current and a low-resistance part 2B made of a material with a lower electrical resistance than the pure spin current generation part. At least a part of the pure spin current generation part can be in contact with the second ferromagnetic metal layer 1. The configuration shown in FIG. 12 is an example in which the configuration of the spin-orbit torque wiring shown in FIG. 3 is applied to the spin current magnetization reversal element of the present invention. The configurations of the spin-orbit torque wiring shown in FIGS. 4 to 6 can be applied to the spin current magnetization reversal element of the present invention.

[0095] As an application example of the spin current magnetization reversal element of the present invention, mainly a magnetoresistive effect element can be mentioned. Therefore, in the components included in the spin current magnetization reversal element of the present invention, all components equivalent to those of the above-described magnetoresistive effect element and the like can be applied.

[0096] Also, the use of the spin current magnetization reversal element of the present invention is not limited to a magnetoresistive effect element, and it can also be applied to other uses. As other uses, for example, the spin current magnetization reversal element can be arranged in each pixel and used in a spatial light modulator that spatially modulates incident light using the magneto-optical effect, or in a magnetic sensor, the magnetic field applied to the easy axis of magnetization of the magnet can be replaced with the spin current magnetization reversal element to avoid the hysteresis effect due to the coercive force of the magnet.

Explanation of Symbols

[0097] 1…Second ferromagnetic metal layer, 2…Spin-orbit torque wiring, 10…Substrate, 20…Magnetoresistive element, 21…First ferromagnetic metal layer, 22…Nonmagnetic layer, 23…Second ferromagnetic metal layer, 23’…Junction (second ferromagnetic metal layer side), 24…Cap layer, 24’…Junction (cap layer side), 30…Wiring, 40, 50, 51, 52…Spin-orbit torque wiring, 40’…Junction (spin-orbit torque wiring side), 41, 41A, 41B…Spin current generation section, 42A, 42B, 42C…Low resistance section, 100, 200, 300…Magnetoresistive element, 101…Spin current magnetization reversal element, I…Current, S1…Upward spin, S2…Downward spin, M 21 ,M 23 …Magnetization, I1…First current path, I2…Second current path, 110…First power supply, 120…Second power supply

Claims

1. a second ferromagnetic metal layer with a variable magnetization direction; a spin-orbit torque wiring that extends in a direction intersecting the plane normal direction of the second ferromagnetic metal layer and is joined to the second ferromagnetic metal layer; having a cap layer between the spin-orbit torque wiring and the second ferromagnetic metal layer, and the spin-orbit torque wiring and the second ferromagnetic metal layer are joined via the cap layer; a configuration in which a spin current flows from the spin-orbit torque wiring through the cap layer to the second ferromagnetic metal layer; the cap layer is made of any material selected from the group consisting of Ru, Ta, Cu, Ag, Au, Mg, and Al; a spin current magnetization reversal element in which the spin-orbit torque wiring contains 3% or less of a magnetic metal.

2. The spin current magnetization reversal element according to claim 1, wherein the cap layer is made of any material selected from the group consisting of Cu, Ag, Mg, and Al.

3. The current density flowing through the spin-orbit torque wiring is less than 1 × 10 ７ A / cm ２ The spin current magnetization reversal element according to any one of claims 1 or 2.

4. The spin-orbit torque wiring includes a pure spin current generation portion made of a material that generates a pure spin current and a low-resistance portion made of a material having a lower electrical resistance than the pure spin current generation portion, and at least a part of the pure spin current generation portion is in contact with the second ferromagnetic metal layer. The spin current magnetization reversal element according to any one of claims 1 to 3.

5. a spin current magnetization reversal element according to any one of claims 1 to 4; a magnetic resistance effect element including a non-magnetic layer joined to the opposite side of the spin-orbit torque wiring of the second ferromagnetic metal layer and a first ferromagnetic metal layer joined to the non-magnetic layer and having a fixed magnetization direction.

6. a magnetic memory including a plurality of magnetic resistance effect elements according to claim 5.

7. A method for magnetization reversal in the magnetic resistance effect element according to claim 5, wherein a current is applied to the power supply of the magnetic resistance effect element after a current is applied to the power supply of the spin-orbit torque wiring.

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