JP7183703B2 - Spin-orbit torque magnetoresistive element and method for manufacturing spin-orbit torque magnetoresistive element - Google Patents

Description

The present invention relates to a spin- orbit torque magnetoresistive element and a method for manufacturing a spin-orbit torque magnetoresistive element .

Tunneling magnetoresistive (TMR) elements that use insulating layers (tunnel barrier layers, barrier layers) as non-magnetic layers, a method of writing (magnetization rotation) using the magnetic field created by current, and the stacking direction of the magnetoresistive effect element A method is known in which writing (magnetization rotation) is performed by utilizing a spin transfer torque (STT) generated by applying a current to a magnetic field. Although the magnetization rotation of the TMR element using the STT is efficient from the viewpoint of energy efficiency, there is a risk of deterioration of the TMR element because a current is applied in the lamination direction of the magnetoresistive effect element in order to cause the magnetization rotation. There is

Therefore, in recent years, attention has focused on spin-orbit torque-type magnetization rotation elements that utilize a pure spin current generated by spin-orbit interaction as a means of enabling magnetization rotation without flowing a current in the lamination direction of a magnetoresistive element. there is When current flows through the spin-orbit torque wiring layer, a pure spin current is generated by the spin-orbit interaction and the Rashba effect at the interface of dissimilar materials. This pure spin current induces a spin-orbit torque (SOT), which causes magnetization rotation of the ferromagnet arranged on the spin-orbit torque wire. A pure spin current is generated by an equal number of spin-up electrons and spin-down electrons flowing in opposite directions, and the charge flow is canceled. Therefore, the rotating current flowing through the magnetoresistive effect element is zero, and it is expected that the magnetoresistive effect element will last longer. In the spin-orbit torque type magnetization rotation element, the higher the current density applied to the spin-orbit torque wiring, the easier the magnetization rotation can be performed.

Spin-orbit torque magnetization rotation elements are classified into several types according to the relationship between the direction of the current flowing in the spin-orbit torque wiring and the direction of the easy axis of magnetization of the ferromagnet. A spin-orbit torque-type magnetization rotating element includes a spin-orbit torque wiring layer extending in the X direction and a first ferromagnetic layer laminated on one surface thereof. According to the orientation of the axis of easy magnetization of the first ferromagnetic layer, it is classified into X-type, Y-type, and Z-type magnetization rotary elements. The X-type magnetization rotating element has an easy axis of magnetization in the same X direction as the spin-orbit torque wiring layer. The Y-shaped magnetization rotating element has an easy axis of magnetization in the Y direction perpendicular to the X direction in the in-plane direction. The Z-type magnetization rotation element has an axis of easy magnetization in the Z direction (stacking direction) perpendicular to the in-plane direction. The X-type and Z-type magnetization rotation elements require a short time for magnetization rotation and can operate at high speed. In addition, since the spin-orbit torque wiring layer of the X-type magnetization rotation element has the major axis in the X direction, the width in the Y direction can be narrowed. Therefore, the X-shaped rotating magnetization element can be reversed in magnetization with less current than the Y-shaped rotating magnetization element. However, X-type and Z-type magnetization rotation elements require external magnetic fields in the Z and X directions, respectively, to be applied to the elements to assist the magnetization rotation. Therefore, the X-type and Z-type magnetization rotating elements have problems in terms of energy consumption and integration. On the other hand, in the case of the Y-type magnetization rotation element, although an external magnetic field is not required to assist magnetization rotation, the time required for magnetization rotation is long and the width in the Y direction is wide, so the current required for magnetization reversal is large. There is a drawback.

In order to solve this problem, an XY-type magnetization rotating element has been proposed in which the axis of easy magnetization of the first ferromagnetic layer is tilted with respect to both the X direction and the Y direction (for example, Non-Patent Document 1). . FIG. 11 shows such an XY-type magnetization rotation element 501. As shown in FIG. The XY magnetization rotating element 501 includes a spin-orbit torque wiring layer 502 , a first ferromagnetic layer 504 and an electrode 506 . The first ferromagnetic layer 504 and the electrodes 506 are laminated on one surface of the spin-orbit torque wiring layer 502, and the electrodes 506 sandwich the first ferromagnetic layer 504 in plan view. Also, the first ferromagnetic layer 504 has a long axis inclined with respect to the X direction and the Y direction in a plan view, unlike the spin-orbit torque wiring layer 502 having a long axis in the X direction. The easy magnetization axis 508 of the first ferromagnetic layer 504 is oriented parallel to the long axis of the first ferromagnetic layer 504 due to shape anisotropy.

Since the XY-type magnetization rotation element 501 configured in this way has a Y-direction component in the axis of easy magnetization, magnetization rotation is caused without an external magnetic field being applied. In addition, since the axis of easy magnetization has an X-direction component, the time required for magnetization rotation is shorter than that of the Y-type magnetization rotating element, making it suitable for high-speed operation.

S. Fukami, et al., Nature Nanotechnology, DOI: 10.1038/NNANO.2016.29 Supplement

However, in the XY magnetization rotating element as shown in FIG. 11, since the long axis of the first ferromagnetic layer is inclined with respect to the X direction and the Y direction, the width of the spin orbit torque wiring layer in the Y direction is large. Become. Therefore, there is a drawback that the current density flowing through the spin-orbit torque wiring layer is reduced and the current required for magnetization rotation is increased.

The present invention has been made in view of the above problems, and is a spin-orbit torque type magnetization rotation element capable of causing magnetization rotation without increasing the current flowing through the spin-orbit torque wiring layer and without applying an external magnetic field. , a method of manufacturing a spin-orbit torque magnetoresistive element and a spin-orbit torque magnetization rotation element.

The present inventors made the long axis of the first ferromagnetic layer coincident with the long axis of the spin-orbit torque wiring layer, while tilting only the easy magnetization axis of the first ferromagnetic layer from the long axis of the spin-orbit torque wiring layer. As a result, the width of the spin-orbit torque wiring layer can be reduced, the current flowing through the spin-orbit torque wiring layer can be reduced, and magnetization rotation can be easily performed without applying an external magnetic field. That is, the present invention provides the following means in order to solve the above problems.

(1) A spin-orbit torque type magnetization rotating element according to a first aspect includes a spin-orbit torque wiring layer extending in the X direction, and a first ferromagnetic layer laminated on the spin-orbit torque wiring layer, The first ferromagnetic layer has shape anisotropy, has a major axis in the X direction, and in the plane in which the spin-orbit torque wiring layer extends, the easy axis of magnetization of the first ferromagnetic layer is in the X direction and the X direction. It is tilted with respect to the Y direction perpendicular to the direction.

(2) In the spin-orbit torque-type magnetization rotating element according to the above aspect, the first ferromagnetic layer may be a HoCo alloy, SmFe alloy, FePt alloy, CoPt alloy, or CoCrPt alloy.

(3) A spin-orbit torque magnetoresistive element according to a second aspect is arranged on the opposite side of the spin-orbit torque wiring layer of the first ferromagnetic layer from the spin-orbit torque magnetoresistive element according to the above aspect. , a second ferromagnetic layer having a fixed magnetization direction, and a non-magnetic layer disposed between the first ferromagnetic layer and the second ferromagnetic layer.

(4) The spin-orbit torque magnetoresistive element according to the above aspect may further include a third ferromagnetic layer disposed between the first ferromagnetic layer and the nonmagnetic layer.

(5) In the spin-orbit torque magnetoresistive element according to the aspect described above, the first ferromagnetic layer may include a diffusion prevention layer on the surface of the first ferromagnetic layer on the nonmagnetic layer side.

(6) In the spin-orbit torque magnetoresistive element according to the aspect described above, the anti-diffusion layer may contain a non-magnetic heavy metal.

(7) In the spin-orbit torque-type magnetoresistive element according to the aspect described above, the diffusion prevention layer may have a thickness not greater than twice the ion radius of the element forming the diffusion prevention layer.

(8) A method for manufacturing a spin-orbit torque type rotating magnetization element according to a third aspect is a method for manufacturing a spin-orbit torque type rotating magnetization element according to the above aspect, wherein at least the first ferromagnetic layer is formed of Y A film is formed in a state in which a magnetic field is applied in a direction including a direction.

(9) The manufacturing method according to the above aspect may include the step of annealing with a magnetic field applied in a direction including the Y direction after forming at least the first ferromagnetic layer.

(10) A method for manufacturing a spin-orbit torque-type rotating magnetization element according to a fourth aspect is a method for manufacturing a spin-orbit torque-type rotating magnetization element according to the above aspect, wherein at least a first ferromagnetic layer is formed. After that, annealing is performed while a magnetic field is applied in directions including the Y direction.

According to the spin-orbit torque-type magnetization rotation element according to the aspect described above, it is possible to cause magnetization rotation without increasing the current flowing through the spin-orbit torque wiring layer and without applying an external magnetic field.

1 is a perspective view schematically showing a spin-orbit torque-type magnetized rotating element according to an embodiment of the present invention; FIG. FIG. 2 is a plan view schematically showing the spin-orbit torque-type magnetization rotation element according to FIG. 1; 1 is a plan view schematically showing a method of manufacturing a spin-orbit torque-type magnetized rotating element according to an embodiment of the present invention; FIG. 1 is a cross-sectional view schematically showing a spin-orbit torque-type magnetoresistance effect element according to an embodiment of the present invention; FIG. FIG. 5 is a plan view schematically showing the spin-orbit torque-type magnetoresistive effect element according to FIG. 4; FIG. 5 is a plan view schematically showing a magnetization reversal state of the spin-orbit torque-type magnetoresistance effect element according to FIG. 4 ; 1 is a cross-sectional view schematically showing a spin-orbit torque-type magnetoresistance effect element according to an embodiment of the present invention; FIG. 1 is a cross-sectional view schematically showing a spin-orbit torque-type magnetoresistance effect element according to an embodiment of the present invention; FIG. FIG. 9 is a plan view schematically showing the spin-orbit torque-type magnetoresistive effect element according to FIG. 8; FIG. 11 is a plan view of a magnetic recording array according to a fourth embodiment; FIG. 4 is a plan view schematically showing a conventional spin-orbit torque-type magnetization rotating element; FIG. 10 is a perspective view schematically showing another example of a spin-orbit torque-type magnetization rotating element;

Hereinafter, the present invention will be described in detail with appropriate reference to the drawings. In the drawings used in the following description, there are cases where characteristic portions are enlarged for convenience in order to make it easier to understand the features of the present invention, and the dimensional ratios of each component may differ from the actual ones. be. The materials, dimensions, etc. exemplified in the following description are examples, and the present invention is not limited to them, and can be implemented with appropriate changes within the scope of the present invention.

(Spin-orbit torque type magnetized rotating element)
FIG. 1 is a perspective view schematically showing a spin-orbit torque-type magnetized rotating element 1 according to one aspect of the present invention. FIG. 2 is a plan view schematically showing the spin-orbit torque-type magnetized rotating element 1 according to FIG. A spin-orbit torque-type magnetization rotating element 1 according to one aspect of the present invention includes a spin-orbit torque wiring layer 2, a first ferromagnetic layer 4 laminated on the spin-orbit torque wiring layer 2, and a first ferromagnetic layer 4. and electrodes 6 laminated on the spin orbit torque wiring layer 2 with the magnetic layer 4 interposed therebetween. Hereinafter, the direction in which the long axis of the spin-orbit torque wiring layer 2 extends is the X-direction, and the direction orthogonal to the X-direction in the plane in which the spin-orbit torque wiring layer 2 extends is the Y-direction, or either the X-direction or the Y-direction. Let the direction perpendicular to also be the Z direction. In FIG. 1, the stacking direction of the first ferromagnetic layer 4 is the Z direction. The first ferromagnetic layer 4 has shape anisotropy with its long axis extending in the X direction. The first ferromagnetic layer 4 also has a magnetization 8 along the easy axis that is tilted with respect to the X and Y directions.

<Spin orbit torque wiring>
The spin-orbit torque wiring layer 2 extends in the X direction. The spin-orbit torque wiring layer 2 is connected to one surface of the first ferromagnetic layer 4 in the Z direction. The spin-orbit torque wiring layer 2 may be directly connected to the first ferromagnetic layer 4, or may be connected via another layer.

A layer interposed between the spin-orbit torque wiring layer 2 and the first ferromagnetic layer 4 preferably does not dissipate spins propagating from the spin-orbit torque wiring layer 2 . For example, it is known that silver, copper, magnesium, aluminum, etc. have a long spin diffusion length of 100 nm or more and are difficult to dissipate spins.

Moreover, the thickness of this layer is preferably equal to or less than the spin diffusion length of the substance constituting the layer. If the thickness of the layer is equal to or less than the spin diffusion length, spins propagating from the spin-orbit torque wiring layer 2 can be sufficiently transmitted to the first ferromagnetic layer 4 .

The spin orbit torque wiring layer 2 is made of a material that generates a spin current by the spin Hall effect when current flows. As such a material, it suffices if it has a structure in which a spin current is generated in the spin orbit torque wiring layer 2 . Therefore, the material is not limited to a material composed of a single element, and may be composed of a portion composed of a material that generates a spin current and a portion composed of a material that does not generate a spin current.

A phenomenon in which a spin current is induced by bending the first spin S1 and the second spin S2 in a direction orthogonal to the direction of the current based on the spin-orbit interaction when an electric current is passed through the material is referred to as spin called the Hall effect. The normal Hall effect and the spin Hall effect are common in that moving (moving) charges (electrons) can bend the direction of movement (moving). In contrast to the spin Hall effect, the direction of movement is bent only by the movement of electrons (current flow) without the presence of a magnetic field.

Since the number of electrons of the first spin S1 and the number of electrons of the second spin S2 are equal in a nonmagnetic material (material that is not a ferromagnetic material), the first ferromagnetic layer 8 of the spin-orbit torque wiring layer 2 is arranged in the figure. The number of electrons of the first spins S1 going in the direction of the provided surface is equal to the number of electrons of the second spins S2 going in the direction opposite to the electrons of the first spins S1. So the current as a net flow of charge is zero. A spin current without this electric current is particularly called a pure spin current.

Here, if 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 J _S , then J _S =J _↑ −J _↓ . In FIG. 1, _JS flows upward in the drawing as a pure spin current. where J _S is the electron flow with 100% polarizability.

The spin-orbit torque wiring layer 2 may contain a non-magnetic heavy metal. Here, heavy metal is used to mean a metal having a specific gravity higher than yttrium. The spin-orbit torque wiring layer 2 may consist only of a non-magnetic heavy metal.

In this case, the non-magnetic heavy metal is preferably a non-magnetic metal having an atomic number of 39 or higher and having d-electrons or f-electrons in the outermost shell. 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 2 may be made only of a non-magnetic metal with a high atomic number of 39 or more having d-electrons or f-electrons in the outermost shell.

Normally, when an electric current is passed through a metal, all electrons move in the opposite direction to the electric current, regardless of their spin direction. Because of the large spin-orbit interaction, the direction of electron movement depends on the electron spin direction due to the spin Hall effect, and a pure spin current J _S is likely to occur.

Also, the spin-orbit torque wiring layer 2 may contain a magnetic metal. A magnetic metal refers to a ferromagnetic metal or an antiferromagnetic metal. This is because when a small amount of magnetic metal is contained in the non-magnetic metal, the spin-orbit interaction is enhanced, and the spin current generation efficiency with respect to the current flowing through the spin-orbit torque wiring layer 2 can be increased. The spin-orbit torque wiring layer 2 may consist only of an antiferromagnetic metal.

Since the spin-orbit interaction is caused by the intrinsic internal field of the material of the spin-orbit torque wiring material, a pure spin current also occurs in non-magnetic materials. When a small amount of magnetic metal is added to the spin-orbit torque wiring material, the magnetic metal itself scatters flowing electron spins, thereby improving the spin current generation efficiency. However, if the amount of the magnetic metal added is too large, the generated spin current is scattered by the added magnetic metal, resulting in a stronger effect of reducing the spin current. Therefore, it is preferable that the molar ratio of the magnetic metal to be added is sufficiently smaller than the molar ratio of the main component of the spin generation portion in the spin-orbit torque wiring. As a guideline, the molar ratio of the magnetic metal to be added is preferably 3% or less.

Also, the spin-orbit torque wiring layer 2 may include a topological insulator. The spin-orbit torque wiring layer 2 may consist of only a topological insulator. A topological insulator is a material whose interior is an insulator or a high resistance material, but whose surface has a spin-polarized metallic state. Matter has something like an internal magnetic field called spin-orbit interaction. Therefore, a new topological phase emerges due to the effect of spin-orbit interaction even without an external magnetic field. This is a topological insulator, and pure spin current can be generated with high efficiency by strong spin-orbit interaction and inversion symmetry breaking at the edge.

Examples of topological insulators include SnTe, Bi _1.5 Sb _0.5 Te _1.7 Se _1.3 , TlBiSe ₂ , Bi ₂ Te ₃ , Bi _1-x Sb _x , (Bi _1-x Sb _x ) ₂ Te ₃ and the like are preferred. These topological insulators can generate spin currents with high efficiency.

<First ferromagnetic layer>
The first ferromagnetic layer 4 is laminated on the spin-orbit torque wiring layer 2 in the Z direction orthogonal to the X direction. The first ferromagnetic layer 4 has shape anisotropy with its major axis extending in the X direction. In addition, the first ferromagnetic layer 4 has magnetization 8 having an easy axis of magnetization in a direction inclined with respect to the X and Y directions in the plane on which the spin-orbit torque interconnection layer 2 extends. The first ferromagnetic layer 4 preferably contains, for example, HoCo alloy, SmFe alloy, FePt alloy, CoPt alloy, CoCrPt alloy. The material of the first ferromagnetic layer 4 is preferably a tetragonal magnetic material in which the c-axis length is shorter than the a-axis length. When the c-axis length is shorter than the a-axis length, the axis of easy magnetization of the first ferromagnetic layer 4 tends to be oriented in the in-plane direction. For example, an Sm--Fe alloy (SmFe ₁₂ ) or the like is preferable. Further, when the c-axis length is longer than the a-axis length, the axis of easy magnetization of the first ferromagnetic layer 4 tends to be oriented in the perpendicular direction. The axis can be oriented in the in-plane magnetic field direction. For example, a Ho—Co alloy (HoCo ₂ ) or the like is preferable. These alloys have a strong magnetocrystalline anisotropy and a large damping constant, so magnetization rotation is less likely to occur. Therefore, the first ferromagnetic layer 4 formed using these materials has a strong data holding power.

The long axis direction of the first ferromagnetic layer 4 and the direction of the easy axis of magnetization of the first ferromagnetic layer 4 are different. In this case, the direction of the axis of easy magnetization of the magnetization 114 of the first ferromagnetic layer 4 can be obtained by, for example, the following method.

The first method is to arrange a plurality of first ferromagnetic layers 4 manufactured under the same conditions and measure their magnetic properties. Magnetic properties can be measured using a vibrating sample magnetometer (VSM), a superconducting quantum interferometer (SQUID), a physical property measuring instrument (PPMS), or the like.

First, a plurality of first ferromagnetic layers 4 having long axes aligned in one direction are arranged in an array, for example. A constant magnetic field is applied to the element assembly of the first ferromagnetic layer 4 from a predetermined direction (reference direction) in the xy plane, and the magnetization of the first ferromagnetic layer 4 in a predetermined direction is measured. By gathering a plurality of first ferromagnetic layers 4, the element assembly exhibits measurable magnetization. This operation is measured at a plurality of points around the in-plane direction of the element assembly while changing the angle of applying the magnetic field.

By plotting the magnitude of magnetization in a predetermined direction on the vertical axis and the tilt angle of the magnetic field applied to the element assembly from the reference direction on the horizontal axis, the magnetization characteristics of the element assembly can be obtained. When the first ferromagnetic layer 4 has an isotropic shape in the xy plane (for example, a circular shape in a plan view), the measured magnetization characteristics draw a sine curve. Further, when the first ferromagnetic layer 4 has a long axis in one direction and the direction of the easy magnetization axis of the first ferromagnetic layer 4 and the long axis direction of the first ferromagnetic layer 4 coincide, the cosine curve (inclination angle at each point in the graph) changes, but the inclination angle indicating the maximum magnetization matches that of the isotropic shape. On the other hand, when the first ferromagnetic layer 4 has a long axis in one direction and the direction of the easy axis of magnetization of the first ferromagnetic layer 4 and the long axis direction of the first ferromagnetic layer 4 are different, the cosine is obtained. As the shape of the curve (inclination angle at each point in the graph) changes, the inclination angle indicating the maximum magnetization shifts. That is, when the inclination angle with respect to the reference direction at the position where the magnetization peaks in the graph is different from the inclination angle with respect to the reference direction of the major axis direction of the first ferromagnetic layer 4, the major axis of the first ferromagnetic layer 4 It can be seen that the direction and the direction of the easy axis of magnetization of the first ferromagnetic layer 4 are different.

A second method is to measure the resistance value of the spin-orbit torque type magnetization rotating element 1 while applying a voltage to the spin-orbit torque type magnetization rotating element 1 . The resistance value of the spin orbit torque type magnetization rotation element 1 is measured while changing the angle of applying a constant magnetic field from a predetermined direction (reference direction) in the xy plane. The resistance value of the spin-orbit torque-type magnetization rotating element 1 is the resistance value between the upper surface of the first ferromagnetic layer 4 and one end of the spin-orbit torque wiring layer 2, and is mainly the resistance of the first ferromagnetic layer 4. value.

When plotting the resistance value of the spin-orbit torque-type rotating magnetization element 1 on the vertical axis and the inclination angle of the magnetic field applied to the first ferromagnetic layer 4 from the reference direction on the horizontal axis, the resistance characteristics of the spin-orbit torque-type rotating magnetization element 1 are obtained. is required. The resistive properties behave similarly to the magnetic properties described above. When the first ferromagnetic layer 4 has an isotropic shape in the xy plane (for example, a circular shape in a plan view), the measured resistance characteristic draws a cosine curve. Further, when the first ferromagnetic layer 4 has a long axis in one direction and the direction of the easy magnetization axis of the first ferromagnetic layer 4 and the long axis direction of the first ferromagnetic layer 4 coincide, the cosine curve (inclination angle at each point in the graph) changes, but the inclination angle showing the maximum resistance matches that of the isotropic shape. On the other hand, when the first ferromagnetic layer 4 has a long axis in one direction and the direction of the easy axis of magnetization of the first ferromagnetic layer 4 and the long axis direction of the first ferromagnetic layer 4 are different, the cosine is obtained. As the shape of the curve (inclination angle at each point in the graph) changes, the inclination angle indicating the maximum magnetization shifts. That is, when the inclination angle with respect to the reference direction at the position where the resistance value peaks in the graph is different from the inclination angle with respect to the reference direction of the long axis direction of the first ferromagnetic layer 4, the length of the first ferromagnetic layer 4 It can be seen that the axial direction and the direction of the easy magnetization axis of the first ferromagnetic layer 4 are different.

<Principle of spin-orbit torque type magnetization rotation element>
Next, the principle of the spin orbit torque type magnetization rotation element 1 will be described with reference to FIGS. 1 and 2. FIG.

As shown in FIG. 1, when a current I is applied to the spin-orbit torque wiring layer 2, the first spin S1 and the second spin S2 are bent by the spin Hall effect. As a result, a pure spin current J _S occurs in the Z direction.

In FIG. 1, since the first ferromagnetic layer 4 is stacked in the Z direction on the spin-orbit torque wiring layer, the pure spin current diffuses and flows into the first ferromagnetic layer 4 . That is, spins are injected into the first ferromagnetic layer 4 . The injected spins give a spin-orbit torque (SOT) to the magnetization 8 of the first ferromagnetic layer 4, causing magnetization rotation. 1 and 2 schematically represent the magnetization 8 of the first ferromagnetic layer 4 as one magnetization located at the center of gravity of the first ferromagnetic layer 4 .

When the direction of spins injected into the ferromagnetic layer is orthogonal to the direction of magnetization, it is necessary to apply an external magnetic field to disturb the symmetry of magnetization in order to cause magnetization rotation. However, in the spin-orbit type magnetization rotating element 1 shown in FIG. The direction of the magnetization 8 of the magnetic layer 4 is inclined with respect to both the X direction and the Y direction, and has an X direction component and a Y direction component. Therefore, since the magnetization 8 has a Y-direction component that is not orthogonal to the spin direction, magnetization rotation can be realized without applying an external magnetic field. If the application of an external magnetic field becomes unnecessary, energy consumption can be reduced and the degree of integration of the device can be improved. Further, since the magnetization 8 has an X-direction component, the spin orbit type magnetization rotation element 1 shown in FIG. 1 can reduce the time required for magnetization rotation, unlike the case where the magnetization 8 extends in the Y direction. suitable for high-speed operation. Further, unlike the conventional XY-type magnetization rotating element shown in FIG. 11, since the long axis of the first ferromagnetic layer 4 is arranged along the X direction, the width of the spin orbit torque wiring layer 2 in the Y direction is can be reduced. Therefore, the XY magnetization rotating element can be realized without lowering the current density, that is, without increasing the current.

(Manufacturing method of spin-orbit torque-type magnetized rotating element)
FIG. 3 is a plan view schematically showing a method for manufacturing a spin-orbit torque-type magnetized rotating element according to an embodiment of the present invention. First, the spin-orbit torque wiring layer 2 is produced on a substrate that serves as a support. The spin-orbit torque wiring layer 2 can be produced using a known film-forming means such as sputtering.

Next, the first ferromagnetic layer 4 is produced. The first ferromagnetic layer 1 can be produced using known film forming means such as sputtering. However, if the first ferromagnetic layer 4 is simply formed into a shape having a long axis along the X direction, the axis of easy magnetization also extends in the X direction due to the shape anisotropy. cannot be realized. Therefore, as shown in FIG. 3, the first ferromagnetic layer 4 is deposited while externally applying a magnetic field B _y having a Y-direction component. Then, the easy magnetization axis of the first ferromagnetic layer 4 is tilted with respect to both the X direction and the Y direction due to the shape anisotropy and the action of the magnetic field _By .

Further, the magnetic field B _y is not applied during the film formation of the first ferromagnetic layer 4, and after the film formation of the first ferromagnetic layer 4, while applying the magnetic field B _y having a Y-direction component, a predetermined temperature, for example, 250 Even if the film is annealed at a temperature of 400° C. to 400° C., an easy axis of magnetization tilted in both the X direction and the Y direction can be obtained. Further, a magnetic field B _y having a Y-direction component is applied when the first ferromagnetic layer 4 is formed, and after the first ferromagnetic layer 4 is formed, a magnetic field B _y having a Y-direction component is further applied, and a predetermined may be annealed at a temperature of, for example, 250 to 400°C.

(Spin-orbit torque magnetoresistive element according to the first embodiment)
FIG. 4 is a cross-sectional view schematically showing the spin-orbit torque-type magnetoresistive effect element 101 according to the first embodiment of the present invention, and FIG. 5 shows the spin-orbit torque-type magnetoresistive effect element 101 according to FIG. FIG. 3 is a schematic plan view; FIG. 6 is a plan view schematically showing the magnetization reversal state of the spin-orbit torque-type magnetoresistance effect element 101 according to FIG.

The spin-orbit torque magnetoresistive element 101 is laminated in the Z-direction perpendicular to the X-direction on the spin-orbit torque wiring layer 102 having a long axis extending in the X-direction, and on the spin-orbit torque wiring layer 102. a first ferromagnetic layer 104 provided; and a spin-orbit torque-type magnetization rotating element provided; and a nonmagnetic layer 110 disposed between the first ferromagnetic layer 104 and the second ferromagnetic layer 112 . The configuration of the spin-orbit torque type rotating magnetization element is the same as the configuration of the spin-orbit torque type rotating magnetization element 1 described with reference to FIGS. 1 and 2, so detailed description thereof will be omitted.

<Second ferromagnetic layer>
The spin-orbit torque magnetoresistive element 101 functions by fixing the magnetization of the second ferromagnetic layer 112 in one direction and changing the magnetization direction of the first ferromagnetic layer 104 relatively. When applied to a coercive force difference type (pseudo spin valve type) MRAM, the coercive force of the second ferromagnetic layer 112 is assumed to be greater than the coercive force of the first ferromagnetic layer 104 . When applied to an exchange bias type (spin valve type) MRAM, the magnetization direction of the second ferromagnetic layer 112 is fixed by exchange coupling with an antiferromagnetic layer.

Further, the spin-orbit torque magnetoresistance effect element 101 is a tunneling magnetoresistance (TMR) element when the nonmagnetic layer 110 is made of an insulator, and is a giant magnetic field when the nonmagnetic layer 110 is made of a metal. It is a resistance (GMR: Giant Magnetoresistance) element.

As the lamination structure of the spin-orbit torque-type magnetoresistive effect element 101, a lamination structure of a known spin-orbit torque-type magnetoresistive effect element can be adopted. For example, each layer may consist of a plurality of layers, or may include other layers such as an antiferromagnetic layer for fixing the magnetization direction of the second ferromagnetic layer 112 . The second ferromagnetic layer 112 is called a fixed layer or a reference layer, and the first ferromagnetic layer 102 is called a free layer or a memory layer.

The second ferromagnetic layer 112 has a long axis along the X direction. The direction of the magnetization 114 can take various directions. For example, as shown in FIG. , along the X direction.

A known material can be used as the material of the second ferromagnetic layer 112, and the same material as that of the first ferromagnetic layer 104 can be used. Since the first ferromagnetic layer 104 is an in-plane magnetization film, the second ferromagnetic layer 112 is also preferably an in-plane magnetization film.

In order to increase the coercive force of the second ferromagnetic layer 112 with respect to the first ferromagnetic layer 104, an antiferromagnetic material such as IrMn or PtMn may be used as the material in contact with the second ferromagnetic layer 112. FIG. Furthermore, in order to prevent the leakage magnetic field of the second ferromagnetic layer 112 from affecting the first ferromagnetic layer 102, a synthetic ferromagnetic coupling structure may be employed.

<Nonmagnetic layer>
A known material can be used for the non-magnetic layer 110 . For example, when the nonmagnetic layer 110 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, materials in which part of Al, Si, and Mg are replaced with Zn, Be, and the like can also be used. Among these materials, MgO and MgAl ₂ O ₄ are materials capable of realizing coherent tunneling, and thus spins can be efficiently injected. If the nonmagnetic layer 110 is made of metal, Cu, Au, Ag, or the like can be used as the material. Furthermore, when the nonmagnetic layer 70 is made of a semiconductor, Si, Ge, CuInSe ₂ , CuGaSe ₂ , Cu(In, Ga)Se ₂ or the like can be used as the material.

Further, the spin-orbit torque-type magnetoresistive element 101 may have other layers. For example, the surface of the first ferromagnetic layer 104 opposite to the nonmagnetic layer 110 may have an underlayer, and the surface of the second ferromagnetic layer 112 opposite to the nonmagnetic layer 110 may have a cap layer. may have.

(Principle of spin-orbit torque-type magnetoresistive element)
Next, the principle of the spin-orbit torque-type magnetoresistive effect element 101 will be described.

FIG. 5 shows a plan view of the spin-orbit torque-type magnetoresistive element 101 having the second ferromagnetic layer 112 with the magnetization 114 aligned with the magnetization 108 . The magnetization 108 of the first ferromagnetic layer 104 is tilted with respect to both the X direction and the Y direction, and in FIG. ing. In this case, the electrical resistance between the first ferromagnetic layer 104 and the second ferromagnetic layer 112 is in a low resistance state.

FIG. 6 shows a plan view of the spin-orbit torque-type magnetoresistive element 101 showing a state in which the magnetization 108 of the first ferromagnetic layer 104 is reversed in the opposite direction to that in FIG. As explained in the principle of the spin-orbit torque type magnetization rotating element, when spins are injected from the spin-orbit torque interconnection layer 102 to the first ferromagnetic layer 104, the magnetization 108 is rotated and reversed. Then, the magnetization 108 is parallel to and opposite to the magnetization 114 of the second ferromagnetic layer 112 (antiparallel). In this case, the electrical resistance between the first ferromagnetic layer 104 and the second ferromagnetic layer 112 is in a high resistance state. Therefore, depending on whether the directions of the magnetization 108 and the magnetization 114 are parallel or antiparallel, the spin-orbit torque-type magnetoresistance effect element 101 has a gap between the first and second ferromagnetic layers 104 and 112. It works as a magnetic memory that holds 0/1 data corresponding to the electrical resistance state.

Here, the case where the magnetization 114 of the second ferromagnetic layer 112 is tilted in the X direction and the Y direction has been described as an example. In this case, the magnetization 108 of the first ferromagnetic layer 104 and the magnetization 114 of the second ferromagnetic layer 112 are completely parallel or completely antiparallel. That is, the MR ratio of the spin-orbit torque-type magnetoresistance effect element 101 can be further increased. However, the magnetization 114 of the second ferromagnetic layer 112 may be along the X direction due to the shape anisotropy of the second ferromagnetic layer 112 . Even in this case, the X-direction component of the magnetization 108 of the first ferromagnetic layer 104 can be parallel or antiparallel to the magnetization 114 of the second ferromagnetic layer 112, so that the magnetization 108 functions as a magnetic memory. can be done.

(Spin-orbit torque-type magnetoresistive element according to the second embodiment)
FIG. 7 is a cross-sectional view schematically showing a spin-orbit torque-type magnetoresistance effect element 201 according to a second embodiment of the present invention. In the spin-orbit torque magnetoresistive element 201 , the first ferromagnetic layer 204 may have a diffusion prevention layer 216 . The diffusion prevention layer 216 may be provided on the surface of the first ferromagnetic layer 204 on the nonmagnetic layer 210 side, or may be provided on any portion of the first ferromagnetic layer 204 in the thickness direction. . In the latter case, the first ferromagnetic layer has a three-layer structure of a lower layer, a diffusion prevention layer, and an upper layer. Other configurations are the same as those of the spin-orbit torque-type magnetoresistance effect element 101 according to the first embodiment, so detailed description thereof will be omitted.

<Diffusion prevention layer>
A non-magnetic heavy metal can be used as the material for the diffusion prevention layer 216 . Annealing causes the second ferromagnetic layer 204 from within the first ferromagnetic layer 204 to be annealed, for example, to achieve a first ferromagnetic layer 204 with magnetization tilted in both the X and Y directions. Elemental diffusion into 212 may occur, degrading the magnetic properties. However, when the anti-diffusion layer 216 is provided on the first ferromagnetic layer 204, the first ferromagnetic layer 204 will not be affected even if annealing is performed at a high temperature after forming the first ferromagnetic layer and the second ferromagnetic layer. Element diffusion from inside the layer 204 to the second ferromagnetic layer 212 can be suppressed, and the magnetic properties are not degraded.

Diffusion prevention layer 216 may also contain a non-magnetic heavy metal. Since heavy metal elements are difficult to move even by annealing, even if annealing is performed at a high temperature after forming the first ferromagnetic layer and the second ferromagnetic layer, the first ferromagnetic layer 204 and the second ferromagnetic layer 212 do not move. Suppresses element diffusion of elements. As a result, deterioration of the magnetic properties of the first ferromagnetic layer 204 and the second ferromagnetic layer 212 can be suppressed.

The anti-diffusion layer 216 can have a thickness less than twice the ionic radius of the constituent elements. Strictly speaking, with a thickness of this order, the heavy metal elements are scattered like islands, and the mixed layer of the upper or lower layer and the heavy metal element serves as the diffusion prevention layer.

(Spin-orbit torque magnetoresistive element according to the third embodiment)
FIG. 8 is a cross-sectional view schematically showing a spin-orbit torque-type magnetoresistive element 301 according to a third embodiment of the present invention, and FIG. 9 is a spin-orbit torque-type magnetoresistive element 301 according to FIG. is a plan view schematically showing the. The spin-orbit torque magnetoresistive element 301 includes a third ferromagnetic layer 318 arranged between the first ferromagnetic layer 304 and the nonmagnetic layer 310 . Other configurations are the same as those of the spin-orbit torque-type magnetoresistive element 301 according to the second embodiment, so detailed description thereof will be omitted. Although FIG. 8 shows a configuration in which the first ferromagnetic layer 304 has the anti-diffusion layer 316, the anti-diffusion layer 316 may be omitted.

CoFeB, CoB, and FeB can be used as the material of the third ferromagnetic layer 318 . The third ferromagnetic layer 318 also has a magnetization 320 along a direction parallel to the magnetization 308 of the first ferromagnetic layer 304 . When the third ferromagnetic layer 318 is disposed between the first ferromagnetic layer 304 and the non-magnetic layer 310, the first ferromagnetic layer 304 and the third ferromagnetic layer 318 are magnetically coupled, It becomes possible to rotate as one magnetization. Therefore, the provision of the third ferromagnetic layer 318 has the effect of increasing the magnetoresistive effect.

(Magnetic recording array according to the fourth embodiment)
FIG. 10 is a plan view of a magnetic recording array 400 according to the fourth embodiment. A magnetic recording array 400 shown in FIG. 10 has spin-orbit torque-type magnetoresistive elements 101 arranged in a 3×3 matrix. FIG. 10 shows an example of a magnetic recording array, and the type, number and arrangement of the spin-orbit torque magnetoresistive effect elements 101 are arbitrary. Moreover, the control unit may exist over all the spin-orbit torque-type magnetoresistive effect elements 101 , or may be provided for each spin-orbit torque-type magnetoresistive effect element 101 .

The domain wall motion type magnetic recording element 100 is connected with one word line WL1-WL3, one bit line BL1-3, and one read line RL1-3.

By selecting word lines WL1 to WL3 and bit lines BL1 to BL3 to which current is applied, a pulse current is applied to the first ferromagnetic layer 104 of an arbitrary spin-orbit torque magnetoresistive element 101 to perform a write operation. By selecting the read lines RL1 to RL3 and the bit lines BL1 to BL3 to which the current is applied, the current is passed in the stacking direction of any spin-orbit torque magnetoresistive element 101 to perform the read operation. The word lines WL1-WL3, the bit lines BL1-3, and the read lines RL1-3 to which the current is applied can be selected by transistors or the like. By recording information in multiple values in each of the spin-orbit torque-type magnetoresistive elements 101, the capacity of the magnetic recording array can be increased.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to specific embodiments, and various can be transformed or changed.

12, the first ferromagnetic layer 14 is circular in plan view from the z-direction. Since the planar view shape is circular, it does not have shape anisotropy.
However, the orientation of the magnetization 18 of the first ferromagnetic layer 14 is tilted with respect to both the X-direction and the Y-direction, and has an X-direction component and a Y-direction component. Therefore, since the magnetization 18 has a Y-direction component that is not orthogonal to the spin direction, magnetization rotation can be realized without applying an external magnetic field even in this configuration. The direction of easy magnetization of the magnetization 18 can be freely set by applying a magnetic field during film formation or annealing even if the magnetization 18 does not have shape anisotropy. The effect associated with this configuration is not limited to the spin-orbit torque type magneto-rotating element, but is the same for the spin-orbit torque type magnetoresistive effect element.

DESCRIPTION OF SYMBOLS 1... Spin orbit torque type magnetization rotation element 2, 102, 202, 302, 502... Spin torque wiring layer 4, 104, 204, 304, 504... First ferromagnetic layer 6, 106, 206, 306, 506 Electrodes 108, 208, 308, 508 Magnetic easy axis of first ferromagnetic layer 110, 210, 310 Nonmagnetic layer 112, 212, 312 Second ferromagnetic layer 114, 314 Second strong Magnetization of magnetic layers 216, 316 Diffusion prevention layer 318 Third ferromagnetic layer 320 Magnetization of third ferromagnetic layer S1 First spin S2 Second spin I Current Js Pure spin current

Claims (8)

a spin orbit torque wiring layer extending in the X direction;
a first ferromagnetic layer laminated on the spin-orbit torque wiring layer;
with
the first ferromagnetic layer has shape anisotropy and has a long axis in the X direction;
In the plane on which the spin-orbit torque wiring layer extends, the easy magnetization axis of the first ferromagnetic layer is inclined with respect to the X direction and the Y direction perpendicular to the X direction,
a spin-orbit torque-type magnetized rotating element ;
a second ferromagnetic layer disposed on the opposite side of the first ferromagnetic layer from the spin-orbit torque wiring layer and having a fixed magnetization direction;
a nonmagnetic layer disposed between the first ferromagnetic layer and the second ferromagnetic layer;
with
A spin-orbit torque magnetoresistive element, wherein the first ferromagnetic layer comprises a diffusion prevention layer on a surface of the first ferromagnetic layer facing the nonmagnetic layer. 2. The spin orbit torque magnetoresistive element according to claim 1, wherein said first ferromagnetic layer is a HoCo alloy, SmFe alloy, FePt alloy, CoPt alloy or CoCrPt alloy. 3. The spin-orbit torque magnetoresistive element according to claim 1 , further comprising a third ferromagnetic layer disposed between said first ferromagnetic layer and said non-magnetic layer. 4. The spin-orbit torque magnetoresistive element according to claim 1, wherein said diffusion prevention layer contains a non-magnetic heavy metal. 5. The spin-orbit torque magnetoresistive element according to claim 1, wherein said anti-diffusion layer has a thickness equal to or less than twice the ion radius of an element forming said anti-diffusion layer. A method for manufacturing the spin-orbit torque-type magnetoresistive element according to any one of claims 1 to 5 ,
A method of manufacturing a spin-orbit torque-type magnetoresistive element , wherein at least the first ferromagnetic layer is formed while a magnetic field is applied in a direction including the Y direction. 7. The method of manufacturing a spin-orbit torque-type magnetoresistive element according to claim 6 , further comprising, after forming at least said first ferromagnetic layer, annealing with a magnetic field applied in a direction including said Y direction. A method for manufacturing the spin-orbit torque-type magnetoresistive element according to any one of claims 1 to 5 ,
A method for manufacturing a spin-orbit torque-type magnetoresistive effect element , wherein annealing is performed in a state in which a magnetic field is applied in a direction including the Y direction after at least the first ferromagnetic layer is formed.

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