JP2019041098A - Spin current magnetoresistive element and magnetic memory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spin current magnetoresistive effect element having excellent write efficiency by magnetization reversal using a spin-orbit torque (SOT) effect. SOLUTION: This spin current magnetic resistance effect element is formed on a first ferromagnetic metal layer, a second ferromagnetic metal layer capable of changing the magnetization direction, a first ferromagnetic metal layer and a second ferromagnetic metal layer. A spin trajectory extending in a first direction intersecting the stacking direction of the magnetic resistance effect element having the sandwiched non-magnetic layer and the magnetic resistance effect element and joining to the second ferromagnetic metal layer. A torque wiring is provided, and the first end portion of the first ferromagnetic metal layer and the second end of 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 portion and the portion. [Selection diagram] Fig. 1

Description

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

  Giant magnetoresistive (GMR) elements composed of a multilayer film of a ferromagnetic layer and a nonmagnetic layer, and tunnel magnetoresistive (TMR) elements using an insulating layer (tunnel barrier layer, barrier layer) as the nonmagnetic layer are known. Yes. In general, a TMR element has a higher element resistance and a higher magnetoresistance (MR) ratio than a GMR element. Therefore, TMR elements are attracting attention as elements for magnetic sensors, high-frequency components, magnetic heads, and nonvolatile random access memories (MRAM).

  The MRAM reads and writes data using the characteristic that the element resistance of the TMR element changes when the directions of magnetization of the two ferromagnetic layers sandwiching the insulating layer change. As a writing method of the MRAM, writing (magnetization reversal) is performed using a magnetic field generated by current, and writing (magnetization) is performed using spin transfer torque (STT) generated by flowing current in the stacking direction of the magnetoresistive effect 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 reversing the magnetization is high. From the viewpoint of the long life of the TMR element, it is desirable that the reversal current density is low. This also applies to 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 reversal current (for example, Non-Patent Document 1). Although this mechanism has not yet been fully clarified, it is thought that the Rashba effect at the interface between pure spin currents or dissimilar materials caused by spin-orbit interaction induces spin-orbit torque (SOT) and causes magnetization reversal. It has been. The pure spin current is generated by the same number of upward spin electrons and downward spin electrons flowing in opposite directions, and the charge flow is canceled out. Therefore, the current flowing through the magnetoresistive effect element is zero, and the lifetime of the magnetoresistive effect element is expected to be extended.

  On the other hand, it is said that in the magnetization reversal using SOT, it is necessary to disturb the symmetry of magnetization that is reversed by applying an external magnetic field. In order to apply an external magnetic field, a magnetic field generation source is required. Providing a separate magnetic field generation source leads to a decrease in the degree of integration of the integrated circuit including the spin current magnetization switching element. Therefore, there is a need for a technique that can reverse magnetization using SOT without applying an external magnetic field. For example, Patent Document 1 describes an element in which the easy axis of magnetization of a recording layer is not uniform in the recording layer and the recording layer includes a plurality of regions having different easy axes of magnetization.

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 effect element described in Patent Document 1 is strongly influenced by the magnetization of the magnetization fixed layer, and the direction of the easy axis of magnetization of the recording layer cannot be made sufficiently non-uniform in the recording layer. For this reason, the write efficiency by magnetization reversal using the spin orbit torque (SOT) effect cannot be sufficiently increased.

  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 excellent in write efficiency by magnetization reversal using the spin orbit torque (SOT) effect.

The inventors defined the position of the end of each layer of the magnetoresistive effect 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 data writing is shunted into the second ferromagnetic metal layer, and spin transfer torque is applied to the magnetization of the second ferromagnetic metal layer, or the movement of the domain wall is used, It has been found that the magnetization of the two ferromagnetic metal layers can be easily reversed. In addition, by providing regions with different easy axes (including a magnetization relaxation region that relaxes non-uniform magnetization) in a portion that does not overlap with the first ferromagnetic metal and has little influence on the MR ratio, It has been found that a decrease in MR ratio can be suppressed.
That is, this invention provides the following means in order to solve the said subject.

(1) A spin current magnetoresistive element according to a first aspect includes a first ferromagnetic metal layer, a second ferromagnetic metal layer capable of changing a magnetization direction, the first ferromagnetic metal layer, and the second strong metal layer. A magnetoresistive effect element having a nonmagnetic layer sandwiched between magnetic metal layers, and extending in a first direction intersecting a stacking direction of the magnetoresistive effect element, and extending to the second ferromagnetic metal layer A spin orbit torque wiring to be bonded, and when viewed from the stacking direction, on either side of the magnetoresistive effect element, a first end of the first ferromagnetic metal layer and the second ferromagnetic metal layer The third end of the nonmagnetic layer is located between the second end of the nonmagnetic layer.

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

(3) In the spin current magnetoresistive effect element according to the aspect described above, a side surface on which the first end portion, the second end portion, and the third end portion exist is in the first direction of the magnetoresistive effect element. May be located.

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

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

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

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

(8) In the spin current magnetoresistive effect element according to the aspect described above, the second ferromagnetism in a direction perpendicular to the first direction and the stacking direction is a distance between the second end and the third end. It may be longer than the width of the metal layer.

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

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

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

  According to the spin current magnetoresistive element and the magnetic memory according to the above aspect, a spin current magnetoresistive element excellent in write efficiency by magnetization reversal using the spin orbit torque (SOT) effect can be obtained.

It is sectional drawing which showed typically the spin current magnetoresistive effect element concerning this embodiment. It is the figure which planarly viewed the spin current magnetoresistive effect element concerning this embodiment from the z direction. It is a schematic diagram for demonstrating a spin Hall effect. It is a cross-sectional schematic diagram of a spin current magnetoresistive effect element in which the end of each layer of the magnetoresistive effect element is present at the same position when viewed from the z direction. 1 is a schematic cross-sectional view of a spin current magnetoresistive effect element illustrated in Patent Document 1. FIG. It is the figure which planarly viewed the spin current magnetoresistive effect element concerning this embodiment from the z direction. It is sectional drawing which showed typically another example of the spin current magnetoresistive effect element which concerns on this embodiment. It is the figure which planarly viewed from the z direction another example of the spin current magnetoresistive effect element concerning this embodiment. It is sectional drawing which showed typically another example of the spin current magnetoresistive effect element which concerns on this embodiment. It is sectional drawing which showed typically an example of the magnetic memory which concerns on this embodiment.

  Hereinafter, the present embodiment will be described in detail with appropriate reference to the drawings. In the drawings used in the following description, in order to make the features easier to understand, the portions that become the features may be shown in an enlarged manner for the sake of convenience, and the dimensional ratios of the respective components may differ from the actual ones. The materials, dimensions, and the like exemplified in the following description are merely examples, and the present invention is not limited to these, and can be implemented with appropriate modifications within the scope of the effects of the present invention.

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

  Hereinafter, the stacking direction of the magnetoresistive effect 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.

<Magnetoresistance effect element>
The magnetoresistive effect element 10 includes a first ferromagnetic metal layer 1, a second ferromagnetic metal layer 2 whose magnetization direction changes, and a non-magnetic material sandwiched between the first ferromagnetic metal layer 1 and the second ferromagnetic metal layer 2. And a magnetic layer 3. The magnetization M 1 of the first ferromagnetic metal layer 1 is fixed relative to the magnetization M 2 of the second ferromagnetic metal layer 2.

  The magnetoresistive element 10 functions by the relative change between 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 magnetoresistive effect element 10 is set to the coercivity of 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 magnetoresistive effect element 10, the magnetization M1 of the first ferromagnetic metal layer 1 in the magnetoresistive effect element 10 is changed with the antiferromagnetic layer. Fix by exchange coupling.

  The magnetoresistive element 10 is a tunneling magnetoresistive (TMR) element when the nonmagnetic layer 3 is made of an insulator, and a giant magnetoresistive (GMR: Giant Magnetoresistance) when the nonmagnetic layer 3 is made of a metal. ) Element.

  As the laminated structure of the magnetoresistive effect element 10, a known laminated structure of the magnetoresistive effect element can be adopted. For example, each layer may be composed of a plurality of layers, or may be provided with other layers 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 memory layer.

  The magnetoresistive effect element 10 shown in FIG. 1 is between the first end e1 in the x direction of the first ferromagnetic metal layer 1 and the second end e2 in the x direction of the second ferromagnetic metal layer 2. The third end e3 in the x direction of the nonmagnetic layer 3 is located.

  In FIG. 1, the first end e1, the second end e2, and the third end e3 satisfy the relationship on both side surfaces of the magnetoresistive element 10 in the x direction. These relationships only need to satisfy the relationship on one side surface in the x direction of the magnetoresistive element 10, but it is particularly preferable to satisfy the relationship on the front surface in the direction of the write current flow. FIG. 2 is a diagram of the spin current magnetoresistive element according to the first embodiment viewed from the z direction. FIG. 2A is a diagram of the spin current magnetoresistance effect element 100 of FIG. 1 viewed from the z direction. FIGS. 2B and 2C are views of a spin current magnetoresistive element according to another example as seen from the z direction.

  Ends (first end e1, second end e2, third end) of each layer (first ferromagnetic metal layer 1, second ferromagnetic metal layer 2, nonmagnetic layer 3) constituting the magnetoresistive effect element 10 When the portion e3) satisfies the relationship, three regions having different magnetic anisotropy 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 in 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 which is sandwiched between the nonmagnetic layer 3 and the spin orbit torque wiring 20 and does not overlap the first ferromagnetic metal layer 1 when viewed from the z direction. The magnetization M22 of the second region A2 is sandwiched between the nonmagnetic layer 3 and the spin orbit torque wiring 20, and has magnetic anisotropy in the z direction under the influence of the interface with these. 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 oppositely.

  The third region A3 of the second ferromagnetic metal layer 2 is a region that does not overlap the first ferromagnetic metal layer 1 and the nonmagnetic 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 anneal the spin current magnetoresistive effect element 100, and influence the crystal structure of the nonmagnetic layer 3 on the second ferromagnetic metal. By giving to the layer 2, it is oriented in the z direction. On the other hand, the magnetization M23 of the third region A3 has no layer stacked in the z direction. As a result, no perpendicular magnetic anisotropy is 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.

  Thus, the second ferromagnetic metal layer 2 has three regions with different easy axes. The perpendicular magnetic anisotropy of the three regions is strong in the order of the first region A1, the second region A2, and the third region A3. Further, the in-plane magnetic anisotropy of the three regions is strong in the order of the third region A3, the second region A2, and the first region A1. If there are regions having different magnetic anisotropy in the second ferromagnetic metal layer 2, the magnetization reversal of the magnetization M2 of the second ferromagnetic metal layer 2 is facilitated. The reason for this will be described later.

  A known material can be used for the material of the first ferromagnetic metal layer 1. For example, a metal selected from the group consisting of Cr, Mn, Co, Fe, and Ni and an alloy that includes one or more of these metals and exhibits ferromagnetism can be used. An alloy containing these metals and at least one element of B, C, and N can also be used. Specific examples include Co—Fe and Co—Fe—B.

In order to obtain a higher output, it is preferable to use a Heusler alloy such as Co ₂ FeSi. The Heusler alloy includes an intermetallic compound having a chemical composition of X ₂ YZ, where X is a transition metal element or noble metal element of Co, Fe, Ni, or Cu group on the periodic table, and Y is Mn, V , Cr or Ti group transition metal or X element species, and Z is a group III to group V typical element. Examples thereof include Co ₂ FeSi, Co ₂ MnSi, and Co ₂ Mn _1-a Fe _a Al _b Si _1-b .

  In order to increase the coercivity of the first ferromagnetic metal layer 1 to the second ferromagnetic metal layer 2, IrMn, An antiferromagnetic material 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, a structure of synthetic ferromagnetic coupling may be used.

Further, when the magnetization direction of the first ferromagnetic metal layer 1 is perpendicular to the laminated surface, it is preferable to use a Co and Pt laminated film. 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 nonmagnetic layer 3 side. _{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 element of B, C, and N are included. Alloys that can be used can be used. Specific examples include Co—Fe, Co—Fe—B, and Ni—Fe. For example, CoFeB alone exhibits in-plane magnetic anisotropy, and exhibits perpendicular magnetic anisotropy when sandwiched between the nonmagnetic layer 3 and the spin orbit torque wiring 20.

A known material can be used for the nonmagnetic layer 3.
For example, when the nonmagnetic layer 3 is made of an insulator (when it is a tunnel barrier layer), as the material, Al ₂ O ₃ , SiO ₂ , MgO, MgAl ₂ O _4, or the like can be used. In addition to these, materials in which a part of Al, Si, Mg is substituted with Zn, Be, or the like can also be used. Among these, since MgO and MgAl ₂ O ₄ are materials that can realize a coherent tunnel, spin can be injected efficiently.
When the nonmagnetic layer 3 is made of a metal, Cu, Au, Ag, or the like can be used as the material.

  The magnetoresistive element 10 may have other layers. For example, the second ferromagnetic metal layer 2 may have an underlayer on the surface opposite to the nonmagnetic layer 3, or the first ferromagnetic metal layer 1 may have a cap on the surface opposite to the nonmagnetic layer 3. 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 are difficult to dissipate spin.

  The thickness of this layer is preferably less than or equal to the spin diffusion length of the material constituting the layer. If 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 effect 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 that generates a pure spin current by a spin Hall effect when a current flows. As such a material, a material that generates a pure spin current in the spin orbit torque wiring 20 is sufficient. Therefore, the material is not limited to a material composed of a single element, and may be a material composed of a portion made of a material that generates a pure spin current and a portion made of a material that does not generate a pure spin current.
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. A 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 applied in the extending direction of the spin orbit torque wiring 20, the first spin S1 oriented on the back side of the paper and the second spin S2 oriented on the front side of the paper are orthogonal to the current, respectively. Bent in the direction. The normal Hall effect and the spin Hall effect are common in that the moving (moving) charge (electrons) can bend in the moving (moving) direction, but the normal Hall effect is the charged particle moving in the magnetic field. In contrast to this, the direction of motion is bent, but the spin Hall effect is greatly different in that the direction of movement is bent only by the movement of electrons (only the current flows) even though no magnetic field exists.

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

  When a current is passed through the ferromagnetic material, the first spin S1 and the second spin S2 are bent in the opposite directions. On the other hand, there is a large number of the first spin S1 and the second spin S2 in the ferromagnet, and as a result, a net flow of charges is generated (voltage is generated). Therefore, the material of the spin orbit torque wiring 20 does not include a material made only of a ferromagnetic material.

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

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

  The spin orbit torque wiring 20 may include a nonmagnetic heavy metal. Here, the heavy metal is used to mean a metal having a specific gravity equal to or higher than yttrium. The spin orbit torque wiring 20 may be made of only nonmagnetic heavy metal.

  In this case, the nonmagnetic heavy metal is preferably a nonmagnetic metal having an 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 a spin Hall effect. The spin orbit torque wiring 20 may be made of only a nonmagnetic metal having an atomic number of 39 or more having d electrons or f electrons in the outermost shell.

Normally, when a current is passed through a metal, all electrons move in the opposite direction of the current regardless of the spin direction. On the other hand, in the nonmagnetic metal having a large atomic number having d electrons or f electrons in the outermost shell, the moving direction of electrons depends on the spin direction of electrons due to the spin Hall effect. A nonmagnetic metal having a large atomic number has a large spin-orbit interaction, and a pure spin current _Js is likely to be generated.

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

  The spin-orbit interaction is caused by the intrinsic internal field of the material of the spin-orbit torque wiring material. Therefore, a pure spin current is generated even with a nonmagnetic 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 spin that flows through the magnetic metal itself is scattered. However, if the added amount of the magnetic metal is increased 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, it is preferable that the molar ratio of the magnetic metal added is sufficiently smaller than the molar ratio of the main component of the pure spin generation part in the spin orbit torque wiring. As a guide, the molar ratio of the magnetic metal added is preferably 3% or less.

  The spin orbit torque wiring 20 may include a topological insulator. The spin orbit torque wiring 20 may be composed only of a topological insulator. A topological insulator is a substance in which the inside of the substance is an insulator or a high-resistance substance, but a spin-polarized metal state is generated on the surface thereof. Substances have something like an internal magnetic field called spin-orbit interaction. Therefore, even without an external magnetic field, a new topological phase appears due to the effect of spin-orbit interaction. This is a topological insulator, and a pure spin current can be generated with high efficiency by strong spin-orbit interaction and breaking 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 a spin current with high efficiency.

  The spin current magnetoresistance effect element 100 may have components other than the magnetoresistance effect element 10 and the spin orbit torque wiring 20. For example, you may have a board | substrate etc. as a support body. The substrate is preferably excellent in flatness, and for example, Si, AlTiC, or the like can be used as a material.

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

The first current I ₂₀ flows in the spin orbit torque wiring 20. The first current I ₂₀ generates a pure spin current as described above, and injects spins oriented in one direction into the second ferromagnetic metal layer 2. The injected spin gives a 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. Second current I _2, the third region A3 having different easy axis, the second region A2, the order of the first region A1, flows in a direction through the area where the magnetization directions are different. That is, the same current flow as the write current of the STT type magnetoresistive effect element is formed. That is, the second current I ₂ is spin polarized when passing through the third region A3. The spin-polarized second current I ₂ gives a spin transfer torque (STT) to the magnetization M22 of the second region A2 and the magnetization M21 of the first region A1.

  Here, the perpendicular magnetic anisotropy of the magnetization M22 in the second region A2 is weaker than the perpendicular magnetic anisotropy of the magnetization M21 in the first region A1. In other words, the magnetization M22 of the second region A2 is more easily reversed than the magnetization M21 of the first region A1. Therefore, first, the magnetization M22 in the second region A2 is reversed by STT and SOT, and the influence is propagated to the magnetization M21 in the first region A1, thereby making it easier to reverse the magnetization M21 in the first region A1. it 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 domain wall movement. Even when the size of the second ferromagnetic metal layer 2 in the x direction is smaller than the size capable of forming the domain wall, the same phenomenon occurs in the micro and the same effect can be obtained.

  FIG. 4 is a schematic cross-sectional view of a spin current magnetoresistive element in which the end portions of the layers of the magnetoresistive element are present at the same position when viewed from the z direction. The spin current magnetoresistive effect element 101 shown in FIG. 4 includes a magnetoresistive effect element 10 A and a spin orbit torque wiring 20. The magnetoresistive effect element 10 </ b> A includes positions of the first end e <b> 11 of the first ferromagnetic metal layer 11, the second end e <b> 12 of the second ferromagnetic metal layer 12, and the third end e <b> 13 of the nonmagnetic layer 13 in the x direction. Match.

The easy axis of magnetization of the second ferromagnetic metal layer 12 of the spin current magnetoresistance effect 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.

  FIG. 5 is a schematic cross-sectional view of the spin current magnetoresistive element shown in Patent Document 1. The spin current magnetoresistive effect element 102 shown in FIG. 5 includes a magnetoresistive effect element 10 </ b> B and a spin orbit torque wiring 20. In the magnetoresistive element 10 </ b> B, the third end e <b> 23 of the nonmagnetic layer 23 and the first end e <b> 21 of the first ferromagnetic metal layer 21 coincide with each other, and the second end e <b> 22 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 area A11 corresponds to the first area A1 in FIG. The second region A12 is a region that does not overlap the first ferromagnetic metal layer 21 and the nonmagnetic layer 23 when viewed from the z direction. The second area A12 corresponds to the third area A3 in FIG.

  Similarly to the spin current magnetoresistance effect element 100 shown in FIG. 1, the spin current magnetoresistance effect element 102 shown in FIG. 5 can give STT and SOT to the magnetization M21 of the second ferromagnetic metal layer 2. 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 of the second region A2 cannot be propagated, and the write efficiency as high as the spin current magnetoresistance effect element 100 shown in FIG. 1 cannot be realized.

  As described above, 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 reversed using SOT and STT. Further, by forming three regions with different easy axes in the second ferromagnetic metal layer 2, magnetization reversal can be performed in order from the portion where magnetization reversal is easy. 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 increased.

  Thus, according to the spin current magnetoresistive effect element 100 according to the present embodiment, the magnetic field magnetization reversal can be performed. By forming three regions having different easy axes in the second ferromagnetic metal layer 2, it is possible to use characteristics superior to the respective magnetization reversals. For example, when the angle between the direction of the injected spin and the direction of the easy axis of magnetization is parallel, magnetic field-free 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 a right angle, high-speed magnetization reversal is enabled by the anti-dumping effect. That is, by forming three regions with different easy 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 magnetoresistance effect element 100 has the following relationship.

  The distance D1 (the width in the x direction of the third region A3) between the third end e3 of the nonmagnetic layer 3 and the second end e2 of the second ferromagnetic metal layer 2 is the first ferromagnetic metal layer 1. It is preferably longer than the distance D2 (the width in the x direction of the second region A2) between the first end e1 and the third end e3. 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 reversed, the influence propagates to the magnetization M21 in the first region A1. Not only the total amount of the magnetization M22 in the second region A2, but the propagation of this effect occurs. Therefore, the width in the x direction of the second region A2 is preferably short. In contrast, the third area A3, it is necessary to sufficiently spin-polarized the second current I _2. Therefore, the third region A3 needs a certain length. When the distance D1 and the distance D2 satisfy the above relationship, it is possible to flow a second current I ₂ which is sufficiently polarized in the first region A1, and the influence of the magnetization M22 of the second region A2 of 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 in the first region A1 and the magnetization M23 in the third region A3. That is, the second region A2 can be regarded as existing as a domain wall. The domain wall width is generally said to be about 20 nm. On the other hand, even if the width of the second region A2 (distance D2 between the first end e1 and the third end e3) is 20 nm or less, the difference in magnetic anisotropy can be alleviated. 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 stacked in the z direction and oriented.

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

  FIG. 6 is a plan view of the spin current magnetoresistance effect element 100 according to the present embodiment as seen from the z direction. 6A shows a case where the distance D1 between the second end e2 and the third end e3 is shorter than the width W of the second ferromagnetic metal layer 2. FIG. FIG. 6B shows a case where the distance D 1 between the second end e 2 and the third end e 3 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 of the second region A2 takes an intermediate state between the magnetization M21 of the first region A1 oriented in the z direction and the magnetization M23 of the third region A3. That is, the magnetization M22 of the second region A2 is oriented in the z direction while being tilted in the y direction.

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

  When the distance D1 is shorter than the width W, the distance D2 between the first end e1 and the third end e3 is also preferably shorter than the width W. If the distance D2 is shorter than the width W, the magnetization M22 of the second region A2 is also easily oriented in the y direction. Since the orientation directions of the magnetization M23 in the third region A3 and the magnetization M22 in the second region A2 are aligned, 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 of the second region A2 takes an intermediate state between the magnetization M21 of the first region A1 oriented in the z direction and the magnetization M23 of the third region A3. That is, the magnetization M22 of the second region A2 is oriented in the z direction while being tilted in the x direction.

The magnetization M23 oriented in the x direction is hardly affected by spins 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, it is possible to strongly spin-polarized the second current I ₂ flowing through the third region A3 in the x-direction. As a result, the action of STT can be strongly applied 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, the distance D2 between the first end e1 and the third end e3 is preferably longer than the width W. If the distance D2 is longer than the width W, the magnetization M22 of the second region A2 is also easily oriented in the x direction. Since the orientation directions of the magnetization M23 in the third region A3 and the magnetization M22 in the second region A2 are aligned, the propagation of the magnetization to the first region A1 becomes smooth.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific embodiments, and various modifications are possible within the scope of the gist of the present invention described in the claims. Deformation / change is possible.

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

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

The spin current magnetoresistive effect element 103 shown in FIG. 7 passes a current I in the x direction during writing. This current I is divided into a first current I ₂₀ and a second current I ₂ , similarly to the spin current magnetoresistance effect element 100 shown in FIG. In the case of the spin current magnetoresistive effect element 103 shown in FIG. 7, since the current component from the third region A3 toward the first region A1 is small, the STT cannot be 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.

  In the spin current magnetoresistive effect element 103 shown in FIG. 7, the magnetization M22 of the second region A2 of the second ferromagnetic metal layer 32 is inclined in the y direction. The direction of spin injected from the spin orbit torque wiring 20 is oriented in the y direction. The magnetization M22 of the second region A2 having the y-direction component is easily affected by this spin and is strongly influenced by the SOT. Therefore, also in the spin current magnetoresistive effect element 103 shown in FIG. 7, STT and SOT can act simultaneously, and the magnetization M2 of the second ferromagnetic metal layer 2 can be easily reversed.

  The spin current magnetoresistive element 100 shown in FIGS. 1 and 2 has a rectangular planar shape when the magnetoresistive element 10 is viewed from the z direction, but the planar shape of the magnetoresistive element 10 is not particularly limited. For example, it may be oval like a magnetoresistive effect element 10D shown in FIG. When the planar shape of the magnetoresistive effect element 10D is an ellipse or a circle, “in any side surface of the magnetoresistive effect element” is rephrased as “in any direction on the side surface of the magnetoresistive effect element”.

Further, like the spin current magnetoresistive element 104 shown in FIG. 9, the side surface of the magnetoresistive element 10E has an inclined surface 10Ea that spreads 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, the side surface is an inclined surface 10 Ea, can flow a second current _{I 2} along the inclined surface 10 Ea. By controlling the flow of the second current I ₂ , the STT can efficiently act on the magnetization of the second ferromagnetic metal layer 42.

  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 magnetoresistance effect elements 100 are connected by a source line SL and a word line WL. Each spin current magnetoresistive effect element constituting the magnetic memory stores data. Since the write efficiency of each spin current magnetoresistive element is enhanced, the magnetic memory is also excellent in write efficiency.

1, 11, 21, 31, 41 ... 1st ferromagnetic metal layer 2, 12, 22, 32, 42 ... 2nd ferromagnetic metal layer 3, 13, 23, 33, 43 ... Nonmagnetic layer 10, 10A, 10B , 10C, 10D, 10E ... magnetoresistive effect element 20 ... spin orbit 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)

A magnetoresistive effect having a first ferromagnetic metal layer, a second ferromagnetic metal layer capable of changing the magnetization direction, and a nonmagnetic layer sandwiched between the first ferromagnetic metal layer and the second ferromagnetic metal layer Elements,
A spin orbit torque wiring extending in a first direction intersecting the stacking direction of the magnetoresistive effect element and joining to the second ferromagnetic metal layer,
As viewed from the stacking direction, on either side of the magnetoresistive element, between the first end of the first ferromagnetic metal layer and the second end of the second ferromagnetic metal layer, A spin current magnetoresistive element in which the third end of the nonmagnetic layer is located.   2. The spin current magnetoresistive element according to claim 1, wherein a distance between the second end and the third end is longer than a distance between the first end and the third end.   3. The spin current magnetoresistance according to claim 1, wherein a side surface on which the first end portion, the second end portion, and the third end portion exist is located in the first direction of the magnetoresistive effect element. Effect element.   The spin current magnetoresistive element according to claim 1, wherein a distance between the second end and the third end is longer than a thickness of the spin orbit torque wiring.   5. The spin current magnetoresistive element according to claim 1, wherein a distance between the first end and the third end is shorter than a thickness of the spin orbit torque wiring.   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 element according to one item.   7. The spin current according to claim 6, wherein a distance between the first end and the third end is shorter than a width of the second ferromagnetic metal layer in the first direction and a direction orthogonal to the stacking direction. Magnetoresistive effect element.   The distance between the second end and the third end is longer than the width of the second ferromagnetic metal layer in the direction perpendicular to the first direction and the stacking direction. The spin current magnetoresistive element according to one item.   9. The spin current according to claim 8, wherein a distance between the first end and the third end is longer than a width of the second ferromagnetic metal layer in the first direction and a direction orthogonal to the stacking direction. Magnetoresistive effect element.   The said side surface of the said magnetoresistive effect element is an inclined surface extended in the said lamination direction toward the said 2nd ferromagnetic metal layer from the said 1st ferromagnetic metal layer, It is any one of Claims 1-9. Spin current magnetoresistive element.   A magnetic memory comprising a plurality of the spin current magnetoresistive elements according to claim 1.

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