JP7095434B2 - Spin current magnetoresistive element and magnetic memory - Google Patents

Description

The present invention relates to a spin current magnetoresistive element and a magnetic memory.

Giant magnetoresistive (GMR) elements consisting of a multilayer film of a ferromagnetic layer and a non-magnetic layer, and tunnel magnetoresistive (TMR) elements using an insulating layer (tunnel barrier layer, barrier layer) as the non-magnetic layer are known. There is. In general, a TMR element has a higher element resistance and a larger magnetoresistive (MR) ratio than a GMR element. Therefore, the TMR element is attracting attention as an element for a magnetic sensor, a high frequency component, a magnetic head, and a non-volatile random access memory (MRAM).

The MRAM reads and writes data by utilizing the characteristic that the element resistance of the TMR element changes when the direction of mutual magnetization of the two ferromagnetic layers sandwiching the insulating layer changes. As a writing method of MRAM, a method of writing (magnetization inversion) using a magnetic field created by a current or a method of writing (magnetization) using a spin transfer torque (STT) generated by passing a current in the stacking direction of a magnetoresistive element. A method of performing inversion) is known.

The magnetization reversal of the TMR element using STT is efficient from the viewpoint of energy efficiency, but the reversal current density for causing the magnetization reversal is high. From the viewpoint of long life of the TMR element, it is desirable that this inverting current density is low. This point is the same for the GMR element.

Therefore, in recent years, attention has been focused on magnetization reversal using a pure spin current generated by spin-orbit interaction as a means for reducing the reversal current (for example, Non-Patent Document 1). Although this mechanism has not been fully clarified yet, it is considered that the Rashba effect at the interface of pure spin current or dissimilar materials caused by spin-orbit interaction induces spin-orbit torque (SOT) and magnetization reversal occurs. Has been done. The pure spin current is created by the same number of upward spin electrons and downward spin electrons flowing in opposite directions, and the charge flow is offset. Therefore, the current flowing through the magnetoresistive element is zero, and it is expected that the life of the magnetoresistive element will be extended.

On the other hand, it is said that in order to reverse the magnetization using SOT, it is necessary to apply an external magnetic field to disturb the symmetry of the magnetization that reverses the magnetization. A source of magnetic field is required to apply an external magnetic field. Providing a separate source for the magnetic field leads to a decrease in the degree of integration of the integrated circuit including the spin current magnetization reversing element. Therefore, there is a demand for a method that can reverse the magnetization by using SOT without applying an external magnetic field. For example, Patent Document 1 describes an element in which the easy-to-magnetize axis of the recording layer is non-uniform in the recording layer and the recording layer has a plurality of regions having different easy-to-magnetize axes.

International Publication No. 2016/021468

I.M.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).

However, the magnetoresistive element described in Patent Document 1 is strongly affected by the magnetization of the magnetization fixed layer, and the direction of the easy axis of magnetization of the recording layer cannot be sufficiently made non-uniform in the recording layer. Therefore, the writing efficiency by magnetization reversal using the spin-orbit torque (SOT) effect could not be sufficiently improved.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a spin current magnetoresistive element having excellent write efficiency by magnetization reversal using a spin-orbit torque (SOT) effect.

The present inventors defined the position of the end of each layer of the magnetoresistive element, and made the direction of the easy axis of magnetization in the second ferromagnetic metal layer more non-uniform. Then, a part of the current at the time of writing the data is shunted into the second ferromagnetic metal layer to give a spin transfer torque to the magnetization of the second ferromagnetic metal layer, or by utilizing the movement of the magnetic domain wall. 2 We have found that the magnetization of the ferromagnetic metal layer can be easily reversed. In addition, by providing a region with a different easy axis of magnetization (including a magnetization relaxation region that alleviates the non-uniformity of magnetization) in a portion that does not overlap with the first ferromagnetic metal and has little effect on the MR ratio, the magnetoresistive element It was found that the decrease in MR ratio can be suppressed.
That is, the present invention provides the following means for solving the above problems.

(1) The spin current magnetic resistance effect element according to the first aspect includes a first ferromagnetic metal layer, a second ferromagnetic metal layer capable of changing the magnetization direction, the first ferromagnetic metal layer, and the second strength. The magnetic resistance effect element having the non-magnetic layer sandwiched between the magnetic metal layers extends in the first direction intersecting the stacking direction of the magnetic resistance effect element, and extends to the second ferromagnetic metal layer. A spin orbit torque wiring to be joined is provided, and the first end portion of the first ferromagnetic metal layer and the second ferromagnetic metal layer are provided on any side surface of the magnetic resistance effect element when viewed from the stacking direction. The third end portion of the non-magnetic layer is located between the second end portion and the second end portion of the non-magnetic layer.

(2) In the spin current magnetoresistive element according to the above aspect, the distance between the second end portion and the third end portion may be longer than the distance between the first end portion and the third end portion. ..

(3) In the spin current magnetoresistive element according to the above aspect, the side surface where the first end portion, the second end portion, and the third end portion are present is in the first direction of the magnetic resistance effect element. It may be located.

(4) In the spin-orbit magnetoresistive element according to the above aspect, the distance between the second end portion and the third end portion may be longer than the thickness of the spin-orbit torque wiring.

(5) In the spin-orbit magnetoresistive element according to the above aspect, the distance between the first end portion and the third end portion may be shorter than the thickness of the spin-orbit torque wiring.

(6) In the spin current magnetic resistance effect element according to the above embodiment, the second ferromagnetism in a direction in which the distance between the second end portion and the third end portion is orthogonal to the first direction and the stacking direction. It may be shorter than the width of the metal layer.

(7) In the spin current magnetic resistance effect element according to the above embodiment, the second ferromagnetism in a direction in which the distance between the first end portion and the third end portion is orthogonal to the first direction and the stacking direction. It may be shorter than the width of the metal layer.

(8) In the spin current magnetic resistance effect element according to the above embodiment, the second ferromagnetism in a direction in which the distance between the second end portion and the third end portion is orthogonal to the first direction and the stacking direction. It may be longer than the width of the metal layer.

(9) In the spin current magnetic resistance effect element according to the above embodiment, the second ferromagnetism in a direction in which the distance between the first end portion and the third end portion is orthogonal to the first direction and the stacking direction. It may be longer than the width of the metal layer.

(10) In the spin current magnetoresistive effect element according to the above aspect, the side surface of the magnetoresistive element is an inclined surface extending in the stacking direction from the first ferromagnetic metal layer toward the second ferromagnetic metal layer. It may be.

(11) The magnetic memory according to the second aspect includes a plurality of spin current magnetoresistive elements according to the above aspect.

According to the spin-orbit magnetoresistive element and the magnetic memory according to the above aspect, it is possible to obtain a spin-orbit magnetic resistance effect element having excellent write efficiency by magnetization reversal using the spin-orbit torque (SOT) effect.

It is sectional drawing which shows schematically the spin current magnetoresistive element which concerns on this embodiment. It is a figure which looked at the plane view from the z direction of the spin current magnetoresistive element which concerns on this embodiment. It is a schematic diagram for demonstrating the spin Hall effect. It is sectional drawing of the spin flow magnetoresistive element which the end part of each layer of the magnetoresistive effect exists at the same position when viewed from the z direction. It is sectional drawing of the spin current magnetoresistive element illustrated in Patent Document 1. It is a figure which looked at the plane view from the z direction of the spin current magnetoresistive element which concerns on this embodiment. It is sectional drawing which showed typically another example of the spin current magnetoresistive element which concerns on this embodiment. It is a figure which looked at the plane view from the z direction another example of the spin current magnetoresistive element which concerns on this embodiment. It is sectional drawing which showed typically another example of the spin current magnetoresistive element which concerns on this embodiment. It is sectional drawing which shows typically the example of the magnetic memory which concerns on this embodiment.

Hereinafter, the present embodiment will be described in detail with reference to the drawings as appropriate. In the drawings used in the following description, the featured portion may be enlarged for convenience in order to make the feature easy to understand, and the dimensional ratio of each component may be different from the actual one. The materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited thereto, and can be appropriately modified and carried out within the range in which the effects of the present invention are exhibited.

(Spin magnetoresistive element)
FIG. 1 is a cross-sectional view schematically showing a spin current magnetoresistive element according to the first embodiment. The spin-flow magnetoresistive element 100 according to the first embodiment has a magnetoresistive effect element 10 and a spin-orbit torque wiring 20.

Hereinafter, the laminating direction of the magnetoresistive element 10 is defined as the z direction, and the first direction in which the spin-orbit torque wiring 20 extends is defined as the x direction. Further, the second direction orthogonal to both the z direction and the x direction is defined as the y direction.

<Magnetic resistance effect element>
The magnetic resistance effect element 10 is a non-ferromagnetic metal layer 1 sandwiched between a first ferromagnetic metal layer 1, a second ferromagnetic metal layer 2 whose magnetization direction changes, a first ferromagnetic metal layer 1 and a second ferromagnetic metal layer 2. It has a magnetic layer 3. The magnetization M1 of the first ferromagnetic metal layer 1 is fixed relative to the magnetization M2 of the second ferromagnetic metal layer 2.

The magnetoresistive effect element 10 functions by relatively changing the orientation of the magnetization M1 of the first ferromagnetic metal layer 1 and the magnetization M2 of the second ferromagnetic metal layer 2. When applied to a coercive force difference type (pseudo spin valve type) MRAM, the coercive force of the first ferromagnetic metal layer 1 of the magnetic resistance effect element 10 is retained by the second ferromagnetic metal layer 2. Make it larger than the magnetic force. When an exchange bias type (spin valve type) MRAM is applied to the magnetic resistance effect element 10, the magnetization M1 of the first ferromagnetic metal layer 1 in the magnetic resistance effect element 10 is referred to as an antiferromagnetic layer. Fixed by exchange coupling.

The magnetic resistance effect element 10 is a tunneling magnetoresistance (TMR) element when the non-magnetic layer 3 is made of an insulator, and a giant magnetoresistance (GMR) when the non-magnetic layer 3 is made of metal. ) It is an element.

As the laminated structure of the magnetoresistive element 10, a known laminated structure of the magnetoresistive element can be adopted. For example, each layer may be composed of a plurality of layers, or may be provided with another layer such as an antiferromagnetic layer for fixing the magnetization direction of the first ferromagnetic metal layer 1. The first ferromagnetic metal layer 1 is called a fixed layer or a reference layer, and the second ferromagnetic metal layer 2 is called a free layer or a storage layer.

The magnetoresistive sensor 10 shown in FIG. 1 is located between the first end portion e1 of the first ferromagnetic metal layer 1 in the x direction and the second end portion e2 of the second ferromagnetic metal layer 2 in the x direction. , The third end e3 of the non-magnetic layer 3 in the x direction is located.

In FIG. 1, the first end portion e1, the second end portion e2, and the third end portion e3 satisfy the relationship on both side surfaces of the magnetoresistive effect element 10 in the x direction. These relationships may be satisfied on one side surface of the magnetoresistive element 10 in the x direction, but it is particularly preferable that the relationship is satisfied on the side surface in front of the flow direction of the write current. FIG. 2 is a view of the spin current magnetoresistive element according to the first embodiment as viewed from the z direction. FIG. 2A is a view of the spin current magnetoresistive element 100 of FIG. 1 as viewed from the z direction. 2 (b) and 2 (c) are views of the spin current magnetoresistive element according to another example as viewed from the z direction.

The ends (first end e1, second end e2, third end) of each layer (first ferromagnetic metal layer 1, second ferromagnetic metal layer 2, non-magnetic layer 3) constituting the magnetoresistive effect element 10. When the part e3) satisfies the relationship, three regions having different magnetic anisotropies are formed in the second ferromagnetic metal layer 2.

The first region A1 of the second ferromagnetic metal layer 2 is a region facing the first ferromagnetic metal layer 1. The magnetization M21 of the first region A1 has a strong magnetic anisotropy in the z direction under the influence of the magnetization M1 of the first ferromagnetic metal layer 1.

The second region A2 of the second ferromagnetic metal layer 2 is a region sandwiched between the non-magnetic layer 3 and the spin-orbit torque wiring 20 and does not overlap with the first ferromagnetic metal layer 1 when viewed from the z direction. The magnetization M22 in the second region A2 is sandwiched between the non-magnetic layer 3 and the spin-orbit torque wiring 20, and is affected by the interface between them and has magnetic anisotropy in the z direction. However, the strength of the magnetic anisotropy of the second region A2 is weaker than that of the first region A1 because the magnetization M1 of the first ferromagnetic metal layer 1 does not exist opposite to each other.

The third region A3 of the second ferromagnetic metal layer 2 is a region that does not overlap with the first ferromagnetic metal layer 1 and the non-magnetic layer 3 when viewed from the z direction. The magnetizations M21 and M22 of the first region A1 and the second region A2 of the second ferromagnetic metal layer 2 annealed the spin current magnetoresistive element 100, and the influence of the crystal structure of the non-magnetic layer 3 was influenced by the second ferromagnetic metal. By giving to layer 2, it is oriented in the z direction. On the other hand, the magnetization M23 in the third region A3 does not have a layer laminated in the z direction. As a result, vertical magnetic anisotropy is not imparted to the third region A3. That is, the magnetization M23 is not oriented in the z direction, but is extremely in-plane oriented in the xy direction.

As described above, the second ferromagnetic metal layer 2 has three regions having different axes of easy magnetization. The vertical magnetic anisotropy of the three regions is stronger in the order of the first region A1, the second region A2, and the third region A3. As for the in-plane magnetic anisotropy of the three regions, the in-plane magnetic anisotropy is stronger in the order of the third region A3, the second region A2, and the first region A1. When regions having different magnetic anisotropies exist in the second ferromagnetic metal layer 2, the magnetization reversal of the magnetization M2 of the second ferromagnetic metal layer 2 becomes easy. The reason for this will be described later.

As the material of the first ferromagnetic metal layer 1, known materials can be used. For example, a metal selected from the group consisting of Cr, Mn, Co, Fe and Ni and an alloy containing one or more of these metals and exhibiting ferromagnetism can be used. Also, alloys containing these metals and at least one or more elements of B, C, and N can be used. Specific examples thereof include Co-Fe and Co-Fe-B.

Further, in order to obtain a higher output, it is preferable to use a Whistler alloy such as Co ₂ FeSi. The Whisler alloy contains an intermetallic compound with a chemical composition of X ₂ YZ, where X is a Co, Fe, Ni or Cu group transition metal element or noble metal element on the periodic table, where Y is Mn, V. , Cr or a transition metal of Group Ti or an elemental species of X, and Z is a typical element of Group III to Group V. For example, Co ₂ FeSi, Co ₂ MnSi, Co ₂ Mn _1-a Fe _a Al _b Si _1-b and the like can be mentioned.

Further, in order to increase the coercive force of the first ferromagnetic metal layer 1 with respect to the second ferromagnetic metal layer 2, IrMn, the surface of the first ferromagnetic metal layer 1 opposite to the second ferromagnetic metal layer 2 is formed. Antiferromagnetic materials such as PtMn may be laminated. In order to prevent the leakage magnetic field of the first ferromagnetic metal layer 1 from affecting the second ferromagnetic metal layer 2, the structure may be a synthetic ferromagnetic coupling.

Further, when the direction of magnetization of the first ferromagnetic metal layer 1 is perpendicular to the laminated surface, it is preferable to use a laminated film of Co and Pt. Specifically, the first ferromagnetic metal layer 1 has FeB (1.0 nm) / Ta (0.2 nm) / [Pt (0.16 nm) / Co (0.16 nm)] in order from the non-magnetic layer 3 side. It can be ₄ / Ru (0.9 nm) / [Co (0.24 nm) / Pt (0.16 nm)] ₆ .

As the material of the second ferromagnetic metal layer 2, 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, these metals and at least one or more elements of B, C and N are contained. It is possible to use an alloy or the like. Specific examples thereof include Co—Fe, Co—Fe—B, and Ni—Fe. For example, CoFeB shows in-plane magnetic anisotropy by itself, and shows vertical magnetic anisotropy when sandwiched between the non-magnetic layer 3 and the spin-orbit torque wiring 20.

A known material can be used for the non-magnetic layer 3.
For example, when the non-magnetic layer 3 is made of an insulator (when it is a tunnel barrier layer), Al ₂ O ₃ , SiO ₂ , MgO, MgAl ₂ O ₄ , and the like can be used as the material. In addition to these, a material in which a part of Al, Si, and Mg is replaced with Zn, Be, or the like can also be used. Among these, _MgO and _MgAl2O4 are materials that can realize a coherent tunnel, so that spin can be efficiently injected.
When the non-magnetic layer 3 is made of metal, Cu, Au, Ag or the like can be used as the material.

The magnetoresistive sensor 10 may have another layer. For example, the base layer may be provided on the surface of the second ferromagnetic metal layer 2 opposite to the non-magnetic layer 3, or the surface of the first ferromagnetic metal layer 1 opposite to the non-magnetic layer 3 may be capped. It may have a layer.

It is preferable that the layer disposed between the spin-orbit torque wiring 20 and the magnetoresistive effect element 10 does not dissipate the spin propagating from the spin-orbit torque wiring 20. For example, it is known that silver, copper, magnesium, aluminum and the like have a long spin diffusion length of 100 nm or more, and spin is difficult to dissipate.

The thickness of this layer is preferably equal to or less than the spin diffusion length of the substance constituting the layer. When the thickness of the layer is equal to or less than the spin diffusion length, the spin propagating from the spin-orbit torque wiring 20 can be sufficiently transmitted to the magnetoresistive element 10.

<Spin-orbit torque wiring>
The spin-orbit torque wiring 20 extends in the x direction. The spin-orbit torque wiring 20 is connected to one surface of the second ferromagnetic metal layer 2 in the z direction. The spin-orbit torque wiring 20 may be directly connected to the second ferromagnetic metal layer 2 or may be connected via another layer.

The spin-orbit torque wiring 20 is made of a material in which a pure spin current is generated by the spin Hall effect when a current flows. As such a material, a material having a configuration in which a pure spin current is generated in the spin-orbit torque wiring 20 is sufficient. Therefore, the material is not limited to a single element, and may be 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 the current based on the spin-orbit interaction when a current is passed through the material.

FIG. 3 is a schematic diagram for explaining the spin Hall effect. FIG. 3 is a cross-sectional view of the spin-orbit torque wiring 20 shown in FIG. 1 cut along the x direction. The mechanism by which a pure spin current is generated by the spin Hall effect will be described with reference to FIG.

As shown in FIG. 3, when a current I is passed in the extending direction of the spin-orbit torque wiring 20, the first spin S1 oriented toward the back side of the paper surface and the second spin S2 oriented toward the front side of the paper surface are orthogonal to the current, respectively. Can be bent in the direction. The normal Hall effect and the spin Hall effect are common in that the moving (moving) charge (electron) can bend the moving (moving) direction, but in the normal Hall effect, the charged particles moving in a magnetic field exert Lorentz force. In contrast to the spinhole effect, which receives and bends the direction of motion, the spinhole effect is significantly different in that the direction of movement is bent only by the movement of electrons (only the flow of electric current) even though there is no magnetic field.

In a non-magnetic material (material that is not a ferromagnetic material), the number of electrons in the first spin S1 and the number of electrons in the second spin S2 are equal, so the number of electrons in the first spin S1 going up and the number of electrons in the second spin S2 in the figure are downward. The number of electrons in the second spin S2 heading is equal. Therefore, the current as a net flow of charge is zero. This spin current without an electric current is particularly called a pure spin current.

When a current is passed through the ferromagnet, the first spin S1 and the second spin S2 are bent in opposite directions at the same point. On the other hand, in the ferromagnet, either the first spin S1 or the second spin S2 is in a large state, and as a result, a net flow of electric charge is generated (voltage is generated). Therefore, the material of the spin-orbit torque wiring 20 does not include a material made of only a ferromagnet.

Here, if the electron flow of the first spin S1 is expressed as J _↑ , the electron flow of the second spin S2 is expressed as J _↓ , and the spin flow is expressed as J _S , it is defined as J _S = J _↑ −J _↓ . In FIG. 3, _JS flows upward in the figure as a pure spin current. Here, _JS is a flow of electrons having a polarizability of 100%.

In FIG. 1, when a ferromagnet is brought into contact with the upper surface of the spin-orbit torque wiring 20, the pure spin current diffuses into the ferromagnet and flows into the ferromagnet. That is, spin is injected into the magnetoresistive element 10.

The spin-orbit torque wiring 20 may contain non-magnetic heavy metals. Here, the heavy metal is used to mean a metal having a specific density equal to or higher than that of yttrium. The spin-orbit torque wiring 20 may be made of only a non-magnetic heavy metal.

In this case, the non-magnetic heavy metal is preferably a non-magnetic metal having a d-electron or an f-electron in the outermost shell and having an atomic number of 39 or more and a large atomic number. This is because such a non-magnetic metal has a large spin-orbit interaction that causes the spin Hall effect. The spin-orbit torque wiring 20 may be made of only a non-magnetic metal having an atomic number 39 or higher and having a d-electron or an f-electron in the outermost shell and having a large atomic number.

Normally, when a current is passed through a metal, all electrons move in the opposite direction of the current, regardless of the direction of their spin. On the other hand, in a non-magnetic metal having a d-electron or an f-electron in the outermost shell and having a large atomic number, the direction of electron movement depends on the direction of electron spin due to the spin Hall effect. A non-magnetic metal having a large atomic number has a large spin-orbit interaction, and a pure spin current J _s is likely to occur.

Further, the spin-orbit torque wiring 20 may contain magnetic metal. The magnetic metal refers to a ferromagnetic metal or an antiferromagnetic metal. This is because when the non-magnetic metal contains a small amount of magnetic metal, the spin-orbit interaction is enhanced, and the spin-orbit generation efficiency with respect to the current flowing through the spin-orbit torque wiring 20 can be increased. The spin-orbit torque wiring 20 may be made of only antiferromagnetic metal.

The spin-orbit interaction is caused by the inherent internal field of the material of the spin-orbit torque wiring material. Therefore, a pure spin current is generated even in a non-magnetic material. When a small amount of magnetic metal is added to the spin-orbit torque wiring material, the spin current generation efficiency is improved because the electron spins flowing by the magnetic metal itself are scattered. However, if the amount of the magnetic metal added is too large, 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, it is preferable that the molar ratio of the added magnetic metal is sufficiently smaller than the molar ratio of the main component of the pure spin generator in the spin-orbit torque wiring. As a guide, the molar ratio of the added magnetic metal is preferably 3% or less.

Further, the spin-orbit torque wiring 20 may include a topological insulator. The spin-orbit torque wiring 20 may consist of only a topological insulator. The topological insulator is a substance in which the inside of the substance is an insulator or a high resistance substance, but a metal state in which spin polarization occurs on the surface thereof. Matter has something like an internal magnetic field called spin-orbit interaction. Therefore, a new topological phase appears due to the effect of spin-orbit interaction even in the absence of an external magnetic field. This is a topological insulator, and a pure spin current can be generated with high efficiency due to strong spin-orbit interaction and breaking of inversion symmetry at the edge.

As the topological insulator, for example, SnTe, Bi _1.5 Sb _0.5 Te _1.7 Se _1.3 , TlBiSe ₂ , Bi ₂ Te ₃ , (Bi _1-x Sb _x ) ₂ Te ₃ and the like are preferable. These topological insulators can generate spin currents with high efficiency.

The spin-orbit magnetoresistive element 100 may have components other than the magnetoresistive effect element 10 and the spin-orbit torque wiring 20. For example, it may have a substrate or the like as a support. The substrate is preferably excellent in flatness, and for example, Si, AlTiC or the like can be used as the material.

(Operation of spin current magnetoresistive element)
The writing operation of the spin current magnetoresistive element 100 will be described with reference to FIG. When writing data to the spin-orbit magnetoresistive element 100, a current I is passed through the spin-orbit torque wiring 20. The current I flowing through the spin-orbit torque wiring 20 is shunted into the first current I ₂₀ and the second current I ₂ at the portion overlapping the magnetoresistive effect element 10 when viewed from the z direction.

The first current I ₂₀ flows in the spin-orbit torque wiring 20. The first current I ₂₀ produces a pure spin current as described above and injects unidirectionally oriented spins into the second ferromagnetic metal layer 2. The injected spin imparts spin-orbit torque (SOT) to the magnetization M21 in the first region A1.

On the other hand, the second current I ₂ flows in the second ferromagnetic metal layer 2. The second current I ₂ flows in the order of passing through the regions having different magnetization directions in the order of the third region A3, the second region A2, and the first region A1 having different magnetization easy axes. That is, the same current flow as the write current of the STT type magnetoresistive element is formed. That is, the second current I ₂ is spin-polarized as it passes through the third region A3. The spin-polarized second current I ₂ applies spin transfer torque (STT) to the magnetization M22 in the second region A2 and the magnetization M21 in the first region A1.

Here, the vertical magnetic anisotropy of the magnetization M22 in the second region A2 is weaker than the vertical magnetic anisotropy of the magnetization M21 in the first region A1. In other words, the magnetization M22 in the second region A2 is more likely to reverse the magnetization than the magnetization M21 in the first region A1. Therefore, it is possible to more easily reverse the magnetization M21 of the first region A1 by first inverting the magnetization M22 of the second region A2 by STT and SOT and propagating the influence to the magnetization M21 of the first region A1. can. When the size of the second ferromagnetic metal layer 2 in the x direction is large enough to form a domain wall, this phenomenon can be confirmed as the domain wall movement. Even when the size of the second ferromagnetic metal layer 2 in the x direction is smaller than the size that can form the domain wall, the same phenomenon occurs microscopically, and the same effect can be obtained.

FIG. 4 is a schematic cross-sectional view of a spin current magnetoresistive element in which the ends of each layer of the magnetoresistive element are present at the same position when viewed from the z direction. The spin-flow magnetoresistive element 101 shown in FIG. 4 includes a magnetoresistive effect element 10A and a spin-orbit torque wiring 20. The magnetoresistive sensor 10A is located at the x-direction of the first end portion e11 of the first ferromagnetic metal layer 11, the second end portion e12 of the second ferromagnetic metal layer 12, and the third end portion e13 of the non-magnetic layer 13. Are in agreement.

The easy axis of magnetization of the second ferromagnetic metal layer 12 of the spin current magnetoresistive element 101 shown in FIG. 4 is uniform in the plane. Therefore, even if the second current I ₂ flows in the second ferromagnetic metal layer 12, STT cannot be given to the magnetization M 2 of the second ferromagnetic metal layer 12.

Further, FIG. 5 is a schematic cross-sectional view of the spin current magnetoresistive element shown in Patent Document 1. The spin-flow magnetoresistive element 102 shown in FIG. 5 includes a magnetoresistive effect element 10B and a spin-orbit torque wiring 20. In the magnetoresistive effect element 10B, the third end portion e23 of the non-magnetic layer 23 and the first end portion e21 of the first ferromagnetic metal layer 21 coincide with each other, and the second end portion e22 of the second ferromagnetic metal layer 22 Protrudes in the x direction.

Two regions are formed in the second ferromagnetic metal layer 22 of the magnetoresistive element 10B shown in FIG. The first region A11 is a region facing the first ferromagnetic metal layer 1. The first region A11 corresponds to the first region A1 in FIG. The second region A12 is a region that does not overlap with the first ferromagnetic metal layer 21 and the non-magnetic layer 23 when viewed from the z direction. The second region A12 corresponds to the third region A3 in FIG.

The spin current magnetoresistive sensor 102 shown in FIG. 5 can also impart STT and SOT to the magnetization M21 of the second ferromagnetic metal layer 2 in the same manner as the spin current magnetic resistance effect element 100 shown in FIG. However, the spin current magnetoresistive element 102 does not have a region corresponding to the second region A2 in FIG. Therefore, the influence of the magnetization M22 in the second region A2 cannot be propagated, and the writing efficiency of the spin current magnetoresistive element 100 shown in FIG. 1 cannot be realized.

As described above, according to the spin magnetoresistive element 100 according to the present embodiment, the magnetization M2 of the second ferromagnetic metal layer 2 can be magnetized and inverted by using SOT and STT. Further, by forming three regions having different magnetization easy axes in the second ferromagnetic metal layer 2, the magnetization reversal can be performed in order from the portion where the magnetization reversal is likely to occur. That is, according to the spin current magnetoresistive element 100 according to the present embodiment, the magnetization M2 of the second ferromagnetic metal layer 2 can be more easily reversed, and the data writing efficiency can be improved.

As described above, according to the spin current magnetoresistive element 100 according to the present embodiment, the magnetic field non-magnetic field magnetization reversal can be performed. By forming three regions having different easy-to-magnetize axes in the second ferromagnetic metal layer 2, it is possible to utilize the characteristics superior to the respective magnetization reversals. For example, when the direction of the injected spin and the angle formed by the direction of the easy axis of magnetization are parallel, non-magnetic field magnetization reversal is possible. On the other hand, when the angle between the direction of the injected spin and the direction of the easy axis of magnetization is right angle, high-speed magnetization reversal is possible by the anti-dumping effect. That is, by forming three regions having different easy-to-magnetize axes in the second ferromagnetic metal layer 2, high-speed magnetization reversal can be performed without a magnetic field.

Further, in order to more easily reverse the magnetization M2 of the first region A1 of the second ferromagnetic metal layer 2, it is preferable that each configuration of the spin current magnetoresistive element 100 has the following relationship.

The distance D1 (width in the x direction of the third region A3) between the third end portion e3 of the non-magnetic layer 3 and the second end portion e2 of the second ferromagnetic metal layer 2 is the first of the first ferromagnetic metal layer 1. It is preferably longer than the distance D2 (width in the x direction of the second region A2) between the first end portion e1 and the third end portion e3. Further, the distance D1 is preferably longer than the thickness T of the spin-orbit torque wiring, and the distance D2 is preferably shorter than the thickness T of the spin-orbit torque wiring.

When the magnetization M22 in the second region A2 is magnetized and inverted, the effect propagates to the magnetization M21 in the first region A1. Propagation of this effect occurs regardless of the total amount of magnetization M22 in the second region A2. Therefore, the width of the second region A2 in the x direction is preferably short. On the other hand, in the third region A3, it is necessary to sufficiently spin-polarize the second current I ₂ . Therefore, the third region A3 needs to have a certain length. When the distance D1 and the distance D2 satisfy the above relationship, a sufficiently spin-polarized second current I ₂ can be passed through the first region A1, and the influence of the magnetization M22 of the second region A2 is exerted on the first region A1. It can be transmitted to the magnetization M21.

The second region A2 is a region that alleviates the difference in magnetic anisotropy between the magnetization M21 of the first region A1 and the magnetization M23 of the third region A3. That is, the second region A2 can also be regarded as existing as a domain wall. The width of the domain wall is generally said to be about 20 nm. On the other hand, the width of the second region A2 (distance D2 between the first end portion e1 and the third end portion e3) can alleviate the difference in magnetic anisotropy even if it is 20 nm or less. This is because the magnetic anisotropy of the first region A1, the second region A2, and the third region A3 is strongly influenced by the layers laminated in the z direction and oriented.

That is, it can be said that the spin current magnetoresistive element 100 according to the present embodiment is an element having a short domain wall width (width of the second region A2, distance D2 between the first end portion e1 and the third end portion e3). The presence of the domain wall favors magnetization reversal, but adversely affects the MR ratio. By shortening the width of the domain wall, it is possible to realize the spin current magnetoresistive element 100 which is easy to reverse the magnetization and has an excellent MR ratio.

Further, FIG. 6 is a plan view of the spin current magnetoresistive element 100 according to the present embodiment from the z direction. FIG. 6A shows a case where the distance D1 between the second end portion e2 and the third end portion e3 is shorter than the width W of the second ferromagnetic metal layer 2. FIG. 6B shows a case where the distance D1 between the second end portion e2 and the third end portion e3 is longer than the width W of the second ferromagnetic metal layer 2.

As shown in FIG. 6A, when the distance D1 is shorter than the width W, the magnetization M23 in the third region A3 of the second ferromagnetic metal layer 2 is oriented in the y direction. The magnetization M22 in the second region A2 takes an intermediate state between the magnetization M21 in the first region A1 oriented in the z direction and the magnetization M23 in the third region A3. That is, the magnetization M22 of the second region A2 is oriented in the z direction while being inclined in the y direction.

As shown in FIG. 2, the direction of the spin injected from the spin-orbit torque wiring 20 is oriented in the y direction. The magnetization M22 in the second region A2 having a component in the y direction is easily affected by this spin and is strongly affected by SOT. When the magnetization M22 is strongly affected by the action of SOT and the magnetization is reversed, the magnetization M21 in the first region A1 is also likely to be magnetized inversion.

When the distance D1 is shorter than the width W, it is preferable that the distance D2 between the first end portion e1 and the third end portion e3 is also shorter than the width W. If the distance D2 is shorter than the width W, the magnetization M22 in the second region A2 also tends to be oriented in the y direction. By aligning the orientation directions of the magnetization M23 of the third region A3 and the magnetization M22 of the second region A2, the propagation of the magnetization to the first region A1 becomes smooth.

On the other hand, as shown in FIG. 6B, when the distance D1 is longer than the width W, the magnetization M23 in the third region A3 of the second ferromagnetic metal layer 2 is oriented in the x direction. The magnetization M22 in the second region A2 takes an intermediate state between the magnetization M21 in the first region A1 oriented in the z direction and the magnetization M23 in the third region A3. That is, the magnetization M22 of the second region A2 is oriented in the z direction while being inclined in the x direction.

The magnetization M23 oriented in the x direction is hardly affected by the spin injected from the spin orbit torque wiring 20 having a component in the y direction. Therefore, the magnetization M23 in the third region A3 is hardly affected by SOT. That is, the second current I ₂ flowing in the third region A3 can be strongly spin-polarized in the x direction. As a result, the action of STT can be strongly given to the magnetization M21 in the first region A1 and the magnetization M22 in the second region A2.

When the distance D1 is longer than the width W, it is preferable that the distance D2 between the first end portion e1 and the third end portion e3 is also longer than the width W. If the distance D2 is longer than the width W, the magnetization M22 in the second region A2 also tends to be oriented in the x direction. By aligning the orientation directions of the magnetization M23 of the third region A3 and the magnetization M22 of the second region A2, the propagation of the magnetization to the first region A1 becomes smooth.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiment, and various aspects are described within the scope of the claims of the present invention. It can be transformed and changed.

In the spin current magnetoresistive element 100 shown in FIGS. 1 and 2, the first end portion e1, the second end portion e2, and the third end portion e3 have a predetermined relationship on the side surface of the magnetoresistive element 10 in the x direction. Meet. The relationship between these ends is not limited to the side surface in the x direction, and may be satisfied on any side surface of the magnetoresistive effect element.

For example, the spin current magnetoresistive element 103 shown in FIG. 7 has a first end portion e31 of the first ferromagnetic metal layer 31, a second end portion e32 of the second ferromagnetic metal layer 32, and a non-magnetic layer 33. The third end portion e33 and the third end portion e33 satisfy a predetermined relationship in the y direction. FIG. 7A is a cross-sectional view of the spin current magnetoresistive effect element 103 cut in the yz plane, and FIG. 7B is a plan view of the spin current magnetic resistance effect element 103 in a plan view from the z direction. ..

The spin current magnetoresistive element 103 shown in FIG. 7 causes a current I to flow in the x direction at the time of writing. This current I is shunted into the first current I ₂₀ and the second current I ₂ in the same manner as the spin current magnetoresistive element 100 shown in FIG. In the case of the spin current magnetoresistive element 103 shown in FIG. 7, since the current component from the third region A3 to the first region A1 is small, the STT cannot be greatly applied to the magnetization M21 in the first region A1. However, since the current component flowing in the y direction is not zero, STT acts on the magnetization M21 in the first region A1.

Further, in the spin current magnetoresistive element 103 shown in FIG. 7, the magnetization M22 of the second region A2 of the second ferromagnetic metal layer 32 is tilted in the y direction. The direction of the spin injected from the spin-orbit torque wiring 20 is oriented in the y direction. The magnetization M22 in the second region A2 having a component in the y direction is easily affected by this spin and is strongly affected by SOT. Therefore, even in the spin current magnetoresistive element 103 shown in FIG. 7, STT and SOT can act at the same time, and the magnetization M2 of the second ferromagnetic metal layer 2 can be easily reversed.

Further, the spin current magnetoresistive element 100 shown in FIGS. 1 and 2 has a rectangular planar shape when the magnetic resistance effect element 10 is viewed from the z direction, but the planar shape of the magnetic resistance effect element 10 is not particularly limited. For example, it may be elliptical or circular as in the magnetoresistive sensor 10D shown in FIG. When the planar shape of the magnetoresistive effect element 10D is elliptical or circular, "on any side surface of the magnetoresistive effect element" is paraphrased as "in any direction of the side surface of the magnetoresistive effect element".

Further, as in the spin current magnetoresistive element 104 shown in FIG. 9, the side surface of the magnetoresistive element 10E is an inclined surface 10Ea extending in the z direction from the first ferromagnetic metal layer 41 toward the second ferromagnetic metal layer 42. May be formed. As shown in FIG. 9, when the side surface is the inclined surface 10Ea, the second current I ₂ can flow along the inclined surface 10Ea. By controlling the flow of the second current I ₂ , the STT can be efficiently acted on the magnetization of the second ferromagnetic metal layer 42.

Further, a plurality of spin current magnetoresistive elements as described above may be arranged to form a magnetic memory (FIG. 10). In the magnetic memory shown in FIG. 10, a plurality of spin current magnetoresistive elements 100 are connected by a source line SL and a word line WL. Each spin magnetoresistive sensor constituting the magnetic memory stores data. Since the writing efficiency of each spin current magnetoresistive element is increased, the magnetic memory is also excellent in writing efficiency.

1,11,21,31,41 ... 1st ferromagnetic metal layer 2,12,22,32,42 ... 2nd ferromagnetic metal layer 3,13,23,33,43 ... Non-magnetic layers 10,10A, 10B , 10C, 10D, 10E ... Magnetic resistance effect element 20 ... Spin trajectory torque wiring e1 ... First end e2 ... Second end e3 ... Third end A1 ... First region A2 ... Second region A3 ... Third region 100, 101, 102, 103, 104 ... Spin current magnetoresistive effect element

Claims (11)

Magnetic resistance effect having a first ferromagnetic metal layer, a second ferromagnetic metal layer capable of changing the magnetization direction, and a non-magnetic layer sandwiched between the first ferromagnetic metal layer and the second ferromagnetic metal layer. With the element
A spin-orbit torque wiring extending in a first direction intersecting the laminating direction of the magnetoresistive effect element and joining to the second ferromagnetic metal layer is provided.
When viewed from the stacking direction, on any side surface of the magnetoresistive element, between the first end portion of the first ferromagnetic metal layer and the second end portion of the second ferromagnetic metal layer, the said. The third end of the non-magnetic layer is located
The first side surface including the first end portion, the second side surface including the second end portion, and the third side surface including the third end portion are in the extending direction of the second ferromagnetic metal layer. Spin current magnetoresistive effect elements that are separated and discontinuous in . The spin current magnetoresistive element according to claim 1, wherein the distance between the second end portion and the third end portion is longer than the distance between the first end portion and the third end portion. The spin current magnetic resistance according to claim 1 or 2, wherein the side surface where the first end portion, the second end portion, and the third end portion are present is located in the first direction of the magnetoresistive element. Effect element. The spin-orbit magnetoresistive element according to any one of claims 1 to 3, wherein the distance between the second end and the third end is longer than the thickness of the spin-orbit torque wiring. The spin-orbit magnetoresistive element according to any one of claims 1 to 4, wherein the distance between the first end portion and the third end portion is shorter than the thickness of the spin-orbit torque wiring. Any of claims 1 to 5, wherein the distance between the second end and the third end is shorter than the width of the second ferromagnetic metal layer in the first direction and the direction orthogonal to the stacking direction. The spin current magnetoresistive effect element according to item 1. The spin current according to claim 6, wherein the distance between the first end portion and the third end portion is shorter than the width of the second ferromagnetic metal layer in the direction orthogonal to the first direction and the stacking direction. Magnetic resistance effect element. Any of claims 1 to 5, wherein the distance between the second end and the third end is longer than the width of the second ferromagnetic metal layer in the first direction and the direction orthogonal to the stacking direction. The spin current magnetoresistive effect element according to item 1. The spin current according to claim 8, wherein the distance between the first end portion and the third end portion is longer than the width of the second ferromagnetic metal layer in the direction orthogonal to the first direction and the stacking direction. Magnetic resistance effect element. The aspect according to any one of claims 1 to 9, wherein the side surface of the magnetoresistive sensor is an inclined surface extending in the stacking direction from the first ferromagnetic metal layer toward the second ferromagnetic metal layer. Spin current magnetoresistive effect element. A magnetic memory including a plurality of spin current magnetoresistive elements according to any one of claims 1 to 10.

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