Domain wall motion element and magnetic array

Abstract

To provide a domain wall moving element and a magnetic array having a large MR ratio and high domain wall controllability.SOLUTION: A domain wall moving element according to an embodiment includes a magnetoresistance effect element having a reference layer, a non-magnetic layer, and a domain wall moving layer, from the side closest to a substrate, and a first magnetization fixed layer and a second magnetization fixed layer that are in contact with the domain wall moving layer and are separated from each other, and the domain wall moving layer includes a ferromagnetic layer including a plurality of insertion layers, and the ferromagnetic layer contains Co and Fe, has perpendicular magnetic anisotropy, and when writing is performed, a writing current is allowed to flow between the first magnetization fixed layer and the second magnetization fixed layer along the magnetic domain wall moving layer .SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a domain wall motion element and a magnetic array. [Background technology]

[0002] The next generation of non-volatile memory is attracting attention as an alternative to flash memory, etc., as the miniaturization of memory is reaching its limits. For example, MRAM (Magnetoresistive Random Access Memory), ReRAM (Resistive Random Access Memory), PCRAM (Phase Change Random Access Memory), etc. are known as next generation non-volatile memories.

[0003] MRAM utilizes resistance value changes caused by changes in the magnetization direction for data recording. Data recording is performed by each of the magnetoresistance change elements that make up the MRAM. For example, Patent Document 1 describes a magnetoresistance change element (domain wall motion element) that can record multi-value data by moving a domain wall in a first ferromagnetic layer (domain wall motion layer). Patent Document 1 also describes that magnetization fixed regions can be easily formed on both ends of the first ferromagnetic layer by utilizing magnetic coupling with a second ferromagnetic layer group. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2009 / 122990 Summary of the Invention [Problem to be solved by the invention]

[0005] A domain wall motion element that can stably express many states can be used for many applications. One way to realize a domain wall motion element that can stably express many states is to increase the resistance change range (MR ratio) of the domain wall motion element. If the resistance change range is large, multiple states can be assigned within the resistance change range, and many states can be stably expressed.

[0006] Another way to realize a domain wall motion element that can stably express many states is to improve the controllability of the domain wall motion of the domain wall motion element. With improved controllability of the domain wall, many states can be assigned to the same resistance change range, and many states can be stably expressed.

[0007] On the other hand, it is difficult to realize a domain wall motion element that has a large MR ratio and high controllability of the domain wall.

[0008] The present invention has been made in view of the above problems, and has an object to provide a domain wall motion element and a magnetic array which have a large MR ratio and high controllability of the domain wall. [Means for solving the problem]

[0009] (1) A domain wall motion element according to a first aspect includes, in order from the side closest to the substrate, a magnetoresistive effect element having a reference layer, a non-magnetic layer, and a domain wall motion layer, and a first magnetization fixed layer and a second magnetization fixed layer each in contact with the domain wall motion layer and spaced apart from each other, the domain wall motion layer includes a ferromagnetic layer including a plurality of insertion layers, the ferromagnetic layer including Co and Fe and having perpendicular magnetic anisotropy, and during writing, a write current is passed along the domain wall motion layer between the first magnetization fixed layer and the second magnetization fixed layer.

[0010] (2) In the domain wall motion element according to the above aspect, the first magnetization pinned layer and the second magnetization pinned layer may have different thicknesses.

[0011] (3) In the domain wall motion element according to the above aspect, the first magnetization fixed layer and the second magnetization fixed layer each have a magnetic coupling layer and a ferromagnetic layer stacked alternately, and the number of layers of the ferromagnetic layers included in the first magnetization fixed layer may be different from the number of layers of the ferromagnetic layers included in the second magnetization fixed layer.

[0012] (4) In the domain wall motion element according to the above aspect, the insertion layer may contain any one selected from the group consisting of MgO, Mg-Al-O, Mg, W, Mo, Ta, Pd, and Pt.

[0013] (5) In the domain wall motion element according to the above aspect, the insertion layer may have a plurality of insertion regions distributed in an island shape.

[0014] (6) In the domain wall motion element according to the above aspect, the first insertion layer which is the closest to the nonmagnetic layer among the insertion layers may contain any one selected from the group consisting of W, Mo, Ta, Pd, and Pt, and any one of the insertion layers other than the first insertion layer may contain MgO or Mg-Al-O.

[0015] (7) In the domain wall motion element according to the above aspect, a first ferromagnetic layer among the ferromagnetic layers included in the domain wall motion layer, which is closest to the non-magnetic layer, may be thicker than the other ferromagnetic layers included in the domain wall motion layer.

[0016] (8) In the domain wall motion element according to the above aspect, the insertion layer included in the domain wall motion layer that is farthest from the nonmagnetic layer may be thicker than the other insertion layers included in the domain wall motion layer.

[0017] (9) In the domain wall motion element according to the above aspect, the lower surfaces of the first magnetization pinned layer and the second magnetization pinned layer may be located below the upper surface of the domain wall motion layer.

[0018] (10) The domain wall motion element according to the above aspect may further include a perpendicular magnetic induction layer, and the perpendicular magnetic induction layer may be located on the domain wall motion layer.

[0019] (11) In the domain wall motion element according to the above aspect, the perpendicular magnetic induction layer may contain any one selected from the group consisting of MgO, Mg-Al-O, Mg, W, Mo, Ta, Pd, and Pt.

[0020] (12) In the domain wall motion element according to the above aspect, the perpendicular magnetic induction layer may be located at least either between the first magnetization fixed layer and the domain wall motion layer or between the second magnetization fixed layer and the domain wall motion layer.

[0021] (13) The domain wall motion element according to the above aspect may further include a first conductive layer in contact with the first magnetization fixed layer and a second conductive layer in contact with the second magnetization fixed layer, and the first conductive layer may fit into a recess formed in an upper surface of the first conductive layer.

[0022] (14) A magnetic array according to a second aspect includes a plurality of domain wall motion elements according to the above aspect. Effect of the Invention

[0023] The domain wall motion element and magnetic array according to the above aspect have a large MR ratio and high controllability of the domain wall. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a configuration diagram of a magnetic array according to a first embodiment. [Diagram 2] 3 is a cross-sectional view of a characteristic portion of the magnetic array according to the first embodiment. FIG. [Diagram 3] 1 is a cross-sectional view of a domain wall motion element according to a first embodiment. [Figure 4] 1 is a plan view of a domain wall motion element according to a first embodiment. [Diagram 5] FIG. 11 is a cross-sectional view of a domain wall motion element according to a second embodiment. [Figure 6] FIG. 11 is a cross-sectional view of a domain wall motion element according to a third embodiment. [Figure 7] FIG. 11 is a cross-sectional view of a domain wall motion element according to a fourth embodiment. [Figure 8] FIG. 13 is a cross-sectional view of a domain wall motion element according to a fifth embodiment. [Figure 9] FIG. 13 is a cross-sectional view of a domain wall motion element according to a sixth embodiment. [Figure 10] FIG. 13 is a cross-sectional view of a modified example of the domain wall motion element according to the sixth embodiment. [Figure 11] FIG. 13 is a cross-sectional view of a domain wall motion element according to a seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The present embodiment will be described in detail below with reference to the drawings as appropriate. The drawings used in the following description may show characteristic parts in an enlarged scale for the sake of convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. They may be modified as appropriate within the scope of the effects of the present invention.

[0026] First, the directions are defined. The x-direction and the y-direction are substantially parallel to one surface of the substrate Sub (see FIG. 2) described later. The x-direction is the direction in which the domain wall motion layer described later extends. The y-direction is perpendicular to the x-direction. The z-direction is the direction from the substrate Sub described later to the domain wall motion element. In this specification, the +z direction may be expressed as "up" and the -z direction as "down", but these expressions are for convenience and do not define the direction of gravity. In this specification, "extending in the x-direction" means, for example, that the dimension in the x-direction is larger than the smallest dimension among the dimensions in the x-direction, y-direction, and z-direction. The same applies to the case of extending in other directions.

[0027] [First embodiment] 1 is a configuration diagram of a magnetic array according to the first embodiment. The magnetic array 200 includes a plurality of domain wall motion elements 100, a plurality of first wirings Wp, a plurality of second wirings Cm, a plurality of third wirings Rp, a plurality of first switching elements SW1, a plurality of second switching elements SW2, and a plurality of third switching elements SW3. The magnetic array 200 can be used, for example, in a magnetic memory, a multiply-accumulate calculator, a neuromorphic device, a spin memristor, and a magneto-optical element.

[0028] <1st wiring, 2nd wiring, 3rd wiring> Each of the first wirings Wp is a write wiring. Each of the first wirings Wp electrically connects a power source to one or more of the domain wall motion elements 100. The power source is connected to one end of the magnetic array 200 during use.

[0029] Each of the second wirings Cm is a common wiring. The common wiring is a wiring that can be used both when writing and reading data. Each of the second wirings Cm electrically connects a reference potential to one or more domain wall motion elements 100. The reference potential is, for example, ground. The second wirings Cm may be provided for each of the multiple domain wall motion elements 100, or may be provided across the multiple domain wall motion elements 100.

[0030] Each of the third wirings Rp is a read wiring. Each of the third wirings Rp electrically connects a power source to one or more of the domain wall motion elements 100. The power source is connected to one end of the magnetic array 200 during use.

[0031] <First switching element, second switching element, third switching element> 1, a first switching element SW1, a second switching element SW2, and a third switching element SW3 are connected to each of the multiple domain wall motion elements 100. The first switching element SW1 is connected between the domain wall motion element 100 and a first wiring Wp. The second switching element SW2 is connected between the domain wall motion element 100 and a second wiring Cm. The third switching element SW3 is connected between the domain wall motion element 100 and a third wiring Rp.

[0032] When the first switching element SW1 and the second switching element SW2 are turned on, a write current flows between the first wiring Wp and the second wiring Cm connected to a specific domain wall motion element 100. When the second switching element SW2 and the third switching element SW3 are turned on, a read current flows between the second wiring Cm and the third wiring Rp connected to a specific domain wall motion element 100.

[0033] The first switching element SW1, the second switching element SW2, and the third switching element SW3 are elements that control the flow of current. The first switching element SW1, the second switching element SW2, and the third switching element SW3 are, for example, an element that uses a phase change of a crystal layer such as a transistor or an Ovonic Threshold Switch (OTS), an element that uses a change in band structure such as a Metal-Insulator Transition (MIT) switch, an element that uses a breakdown voltage such as a Zener diode or an avalanche diode, or an element whose conductivity changes with a change in atomic position.

[0034] Any of the first switching element SW1, the second switching element SW2, and the third switching element SW3 may be shared by the domain wall motion elements 100 connected to the same wiring. For example, when the first switching element SW1 is shared, one first switching element SW1 is provided upstream (one end) of the first wiring Wp. For example, when the second switching element SW2 is shared, one second switching element SW2 is provided upstream (one end) of the second wiring Cm. For example, when the third switching element SW3 is shared, one third switching element SW3 is provided upstream (one end) of the third wiring Rp.

[0035] Fig. 2 is a cross-sectional view of a main part of the magnetic array 200 according to the first embodiment. Fig. 2 is a cross section of one domain wall motion element 100 in Fig. 1 cut along an xz plane passing through the center of the width of the domain wall motion layer 10 in the y direction.

[0036] The first switching element SW1 and the second switching element SW2 shown in Fig. 2 are transistors Tr. The transistor Tr has a gate electrode G, a gate insulating film GI, and a source region S and a drain region D formed in a substrate Sub. The substrate Sub is, for example, a semiconductor substrate. The third switching element SW3 is electrically connected to the third wiring Rp and is, for example, shifted in the y direction in Fig. 2.

[0037] Each of the transistors Tr and the domain wall motion element 100 are electrically connected via wirings w1 and w2. The wirings w1 and w2 include a conductive material. The wiring w1 is a via wiring extending in the z direction. The wiring w2 is an in-plane wiring extending in any direction within the xy plane. The wirings w1 and w2 are formed within an opening in the insulating layer In.

[0038] The insulating layer In is an insulating layer that insulates between the wirings of the multi-layer wiring and between the elements. The domain wall motion element 100 and the transistor Tr are electrically isolated by the insulating layer In, except for the wirings w1 and w2. The insulating layer In is made of, for example, silicon oxide (SiO x ), silicon nitride (SiN x), silicon carbide (SiC), chromium nitride, silicon carbonitride (SiCN), silicon oxynitride (SiON), aluminum oxide (Al2O3), zirconium oxide (ZrO x ) etc.

[0039] Although FIG. 2 shows an example in which the domain wall motion element 100 is located above the substrate Sub with the insulating layer In therebetween, the domain wall motion element 100 may be located on the substrate Sub.

[0040] "Magnetic domain wall motion element" Fig. 3 is a cross-sectional view of the domain wall motion element 100 cut in an xz plane passing through the center in the y direction of the domain wall motion layer 10. Fig. 4 is a plan view of the domain wall motion element 100 viewed from the z direction. The arrows in the figure are an example of the orientation direction of magnetization of a ferromagnetic material.

[0041] The domain wall motion element 100 is on an electrode E which is electrically connected to, for example, the third wiring Rp. The domain wall motion element 100 has, for example, a magnetoresistance effect element 40, a first magnetization pinned layer 50, and a second magnetization pinned layer 60. A first conductive layer 71 is connected to the first magnetization pinned layer 50, and a second conductive layer 72 is connected to the second magnetization pinned layer 60. The first conductive layer 71 and the second conductive layer 72 are part of the wiring w1 in FIG. 2. The periphery of the domain wall motion element 100 is covered with an insulating layer In.

[0042] The magnetoresistance effect element 40 includes a domain wall displacement layer 10, a nonmagnetic layer 20, and a reference layer 30. The magnetoresistance effect element 40 includes the reference layer 30, the nonmagnetic layer 20, and the domain wall displacement layer 10, in this order from the side closer to the substrate Sub. When writing data to the magnetoresistance effect element 40, a write current is passed between the first magnetization pinned layer 50 and the second magnetization pinned layer 60 along the domain wall displacement layer 10. When reading data from the magnetoresistance effect element 40, a current is applied in the z direction of the magnetoresistance effect element 40, and a read current is passed between the electrode E and the domain wall displacement layer 10.

[0043] The domain wall displacement layer 10 extends in the x-direction. The domain wall displacement layer 10 has a plurality of magnetic domains therein, and has a domain wall DW at the boundary between the plurality of magnetic domains. The domain wall displacement layer 10 is, for example, a layer capable of magnetically recording information by changing the magnetic state. The domain wall displacement layer 10 may be called an analog layer or a magnetic recording layer.

[0044] The domain wall displacement layer 10 has a first region A1, a second region A2, and a third region A3. The first region A1 is a region that overlaps with the first magnetization fixed layer 50 when viewed from the z direction. The second region A2 is a region that overlaps with the second magnetization fixed layer 60 when viewed from the z direction. The third region A3 is a region other than the first region A1 and the second region A2 of the domain wall displacement layer 10. The third region A3 is, for example, a region sandwiched between the first region A1 and the second region A2 in the x direction.

[0045] The magnetization of the first region A1 is fixed by the magnetization of the first magnetization fixed layer 50. The magnetization of the second region A2 is fixed by the magnetization of the second magnetization fixed layer 60. The magnetization being fixed means that the magnetization does not reverse during normal operation of the domain wall motion element 100 (when no external force exceeding the expected value is applied). The first region A1 and the second region A2 have, for example, opposite magnetization orientation directions.

[0046] The third region A3 is a region where the magnetization direction changes and the domain wall DW can move. The third region A3 has a first magnetic domain A3a and a second magnetic domain A3b. The first magnetic domain A3a and the second magnetic domain A3b have magnetization orientation directions opposite to each other. The boundary between the first magnetic domain A3a and the second magnetic domain A3b is the domain wall DW. The magnetization of the first magnetic domain A3a is oriented in the same direction as the magnetization of the first region A1, for example. The magnetization of the second magnetic domain A3b is oriented in the same direction as the magnetization of the adjacent second region A2, for example. In principle, the domain wall DW moves within the third region A3 and does not invade the first region A1 and the second region A2.

[0047] When the ratio of the first magnetic domain A3a to the second magnetic domain A3b in the third region A3 changes, the domain wall DW moves. The domain wall DW moves by applying a write current in the x direction of the third region A3. For example, when a write current (e.g., a current pulse) in the +x direction is applied to the third region A3, electrons flow in the -x direction opposite to the current, and the domain wall DW moves in the -x direction. When a current flows from the first magnetic domain A3a to the second magnetic domain A3b, the spin-polarized electrons in the second magnetic domain A3b reverse the magnetization of the first magnetic domain A3a. When the magnetization of the first magnetic domain A3a is reversed, the domain wall DW moves in the -x direction.

[0048] The domain wall displacement layer 10 includes a ferromagnetic layer 11 and an insertion layer 12. The ferromagnetic layers 11 and the insertion layers 12 are alternately stacked. Adjacent ferromagnetic layers 11 are magnetically joined with the insertion layer 12 sandwiched therebetween.

[0049] The ferromagnetic layer 11 contains Co and Fe. The ferromagnetic layer 11 is, for example, a CoFe alloy. The ferromagnetic layer 11 may be an alloy containing Co and Fe and one or more elements of B, C, and N. The ferromagnetic layer 11 is, for example, Co-Fe-B.

[0050] The ferromagnetic layer 11 has perpendicular magnetic anisotropy. The perpendicular magnetic anisotropy means that the axis of easy magnetization is in a direction intersecting (orthogonal to) the film surface. The thickness of each of the ferromagnetic layers 11 is, for example, 1.5 nm or less.

[0051] The ferromagnetic layer 11 is, for example, an alloy containing Co and Fe and having a thickness of 1.5 nm or less. The alloy containing Co and Fe has a larger magnetoresistance effect than a laminate exhibiting perpendicular magnetic anisotropy, such as a laminate film of Co and Ni, a laminate film of Co and Pt, or a laminate film of Co and Pd. Furthermore, the alloy containing Co and Fe exhibits a large magnetoresistance effect if it has a thickness of 1.5 nm or less. If the magnetoresistance effect of the domain wall motion layer 10 is large, the MR ratio of the domain wall motion element 100 becomes large.

[0052] The thicknesses, materials, etc. of the multiple ferromagnetic layers 11 may be the same or different.

[0053] The insertion layer 12 is located between the ferromagnetic layers 11. The insertion layer 12 induces perpendicular magnetic anisotropy in the ferromagnetic layer 11 due to the effect of the interface with the ferromagnetic layer 11.

[0054] The insertion layer 12 includes, for example, any one selected from the group consisting of MgO, Mg-Al-O, Mg, W, Mo, Ta, Pd, and Pt. These materials strengthen the perpendicular magnetic anisotropy in the adjacent ferromagnetic layer 11. When the insertion layer 12 is MgO or Mg-Al-O, the MR ratio of the domain wall motion element 100 is particularly improved. When the insertion layer 12 is any one of Mg, W, Mo, Ta, Pd, and Pt, the resistance value of the domain wall motion element 100 decreases and the power consumption decreases. When the insertion layer 12 is any one of Mo, Ta, Pd, and Pt, spins are injected into the ferromagnetic layer 11 by the spin Hall effect, and the magnetization of the ferromagnetic layer 11 is easily reversed. Mg-Al-O is an oxide of Mg and Al, and means that the composition ratio is not important. Mg-Al-O is, for example, MgAl2O4 with a spinel structure.

[0055] The thickness of the insertion layer 12 is, for example, 1 nm or less. When the insertion layer 12 is sufficiently thin, the magnetic coupling between the adjacent ferromagnetic layers 11 becomes sufficiently strong.

[0056] The materials of the multiple insertion layers 12 may be the same or different. For example, the first insertion layer 12A may include any one selected from the group consisting of W, Mo, Ta, Pd, and Pt, and any one of the insertion layers 12 located above the first insertion layer 12A may include MgO or Mg-Al-O. The first insertion layer 12A is the insertion layer that is the closest to the nonmagnetic layer 20 among the insertion layers 12. The domain wall motion element 100 is processed from above during manufacturing. By arranging MgO or Mg-Al-O, which is hard and difficult to process, on the upper part of the domain wall motion layer 10, the MgO or Mg-Al-O functions as an etching stopper.

[0057] The insertion layer 12 may be one in which a material selected from the group consisting of MgO, Mg-Al-O, Mg, W, Mo, Ta, Pd, and Pt is dispersed in an alloy containing Co and Fe. That is, the insertion layer 12 may be sufficiently thin (at the level of a few atomic layers) and may not constitute a complete layer. For example, the insertion layer 12 may have a plurality of insertion regions in which a material selected from the above material group is dispersed in an alloy containing Co and Fe in an island shape. These materials can strengthen the perpendicular magnetic anisotropy of the insertion layer 12 and the ferromagnetic layer 11 adjacent thereto. The thickness of the insertion layer 12 may be, for example, 1 nm or more. When the insertion layer 12 contains Co and Fe, the magnetic coupling with the adjacent ferromagnetic layer 11 is sufficiently strong even if the insertion layer 12 is thick.

[0058] The nonmagnetic layer 20 is located between the domain wall displacement layer 10 and the reference layer 30. The nonmagnetic layer 20 is laminated on one surface of the reference layer 30.

[0059] The nonmagnetic layer 20 is made of, for example, a nonmagnetic insulator, semiconductor, or metal. Examples of the nonmagnetic insulator include Al2O3, SiO2, MgO, MgAl2O4, and materials in which a part of Al, Si, and Mg is replaced with Zn, Be, or the like. These materials have a large band gap and excellent insulating properties. When the nonmagnetic layer 20 is made of a nonmagnetic insulator, the nonmagnetic layer 20 is a tunnel barrier layer. Examples of the nonmagnetic metal include Cu, Au, Ag, and the like. Examples of the nonmagnetic semiconductor include Si, Ge, CuInSe2, CuGaSe2, Cu(In,Ga)Se2, and the like.

[0060] The thickness of the nonmagnetic layer 20 is, for example, 20 Å or more, and may be 25 Å or more. If the thickness of the nonmagnetic layer 20 is large, the resistance area area (RA) of the domain wall motion element 100 becomes large. The resistance area area (RA) of the domain wall motion element 100 is 1×10 4 Ωμm 2 It is preferable that the value is 5×10 or more. 4 Ωμm 2The resistance area product (RA) of the domain wall motion element 100 is expressed as the product of the element resistance of one domain wall motion element 100 and the element cross-sectional area of ​​the domain wall motion element 100 (the area of ​​a cross section obtained by cutting the nonmagnetic layer 20 in the xy plane).

[0061] The reference layer 30 sandwiches the nonmagnetic layer 20 together with the domain wall displacement layer 10. The reference layer 30 is, for example, on the electrode E. The reference layer 30 may be laminated on the substrate Sub. The reference layer 30 is located so as to overlap with the domain wall displacement layer 10 in the z direction. The magnetization of the reference layer 30 is more difficult to reverse than the magnetization of the third region A3 of the domain wall displacement layer 10. The magnetization of the reference layer 30 is fixed and does not change direction when an external force is applied strong enough to reverse the magnetization of the third region A3. The reference layer 30 is sometimes referred to as a magnetization fixed layer.

[0062] The reference layer 30 includes a ferromagnetic material. The reference layer 30 includes, for example, a material that is likely to provide a coherent tunnel effect between the reference layer 30 and the domain wall displacement layer 10. The reference layer 30 includes, for example, a metal selected from the group consisting of Cr, Mn, Co, Fe, and Ni, an alloy containing one or more of these metals, an alloy containing these metals and at least one or more of the elements B, C, and N, and the like. The reference layer 30 is, for example, Co-Fe, Co-Fe-B, or Ni-Fe.

[0063] The reference layer 30 may be, for example, a Heusler alloy. Heusler alloys are half-metallic and have high spin polarizability. Heusler alloys are intermetallic compounds having a chemical composition of XYZ or X2YZ, where X is a transition metal element or a noble metal element of the Co, Fe, Ni, or Cu group on the periodic table, Y is a transition metal element or an element type of X of the Mn, V, Cr, or Ti group, and Z is a typical element of groups III to V. Examples of Heusler alloys include Co2FeSi, Co2FeGe, Co2FeGa, Co2MnSi, Co2Mn 1-a Fe a Al b S 1-b , Co2FeGe 1-c Ga c etc.

[0064] The reference layer 30 may also have a synthetic structure made up of a ferromagnetic layer and a nonmagnetic layer, or a synthetic structure made up of an antiferromagnetic layer, a ferromagnetic layer, and a nonmagnetic layer. In the latter synthetic structure, the magnetization direction of the reference layer 30 is strongly held by the antiferromagnetic layer. Therefore, the magnetization of the reference layer 30 is less susceptible to external influences. When the magnetization of the reference layer 30 is oriented in the Z direction (the magnetization of the reference layer 30 is made into a perpendicular magnetization film), it is preferable that the reference layer 30 further includes, for example, a Co / Ni laminated film or a Co / Pt laminated film.

[0065] The first magnetization pinned layer 50 and the second magnetization pinned layer 60 are connected to the domain wall motion layer 10. The first magnetization pinned layer 50 and the second magnetization pinned layer 60 are on the domain wall motion layer 10. The first magnetization pinned layer 50 and the second magnetization pinned layer 60 are spaced apart in the x-direction. The first magnetization pinned layer 50 pins the magnetization of the first region A1. The second magnetization pinned layer 60 pins the magnetization of the second region A2.

[0066] The first magnetization pinned layer 50 and the second magnetization pinned layer 60 are, for example, ferromagnetic. The first magnetization pinned layer 50 and the second magnetization pinned layer 60 can be made of, for example, the same material as the reference layer 30. The first magnetization pinned layer 50 and the second magnetization pinned layer 60 are not limited to ferromagnetic. If the first magnetization pinned layer 50 and the second magnetization pinned layer 60 are not made of ferromagnetic material, the current density of the current flowing through the domain wall movement layer 10 in the region overlapping with the first magnetization pinned layer 50 or the second magnetization pinned layer 60 changes suddenly, thereby restricting the movement of the domain wall DW and pinning the magnetization of the first region A1 and the second region A2.

[0067] 4, for example, the width in the y direction of each of the first magnetization pinned layer 50 and the second magnetization pinned layer 60 is wider than the width in the y direction of the domain wall motion layer 10. The boundary between the first magnetization pinned layer 50 or the second magnetization pinned layer 60 and the domain wall motion layer 10 extends in the y direction of the domain wall motion layer 10, so that the magnetic property distribution in the y direction in the domain wall motion layer 10 becomes uniform. When the magnetic property distribution in the y direction in the domain wall motion layer 10 becomes uniform, it is possible to suppress the domain wall DW from tilting with respect to the y direction.

[0068] The shape of each of the first magnetization fixed layer 50 and the second magnetization fixed layer 60 when viewed from the z direction is, for example, a rectangle. The shape of each of the first magnetization fixed layer 50 and the second magnetization fixed layer 60 when viewed from the z direction may be, for example, a circle, an ellipse, an oval, or the like.

[0069] The magnetization direction of each layer of the domain wall motion element 100 can be confirmed by, for example, measuring a magnetization curve. The magnetization curve can be measured, for example, by using MOKE (Magneto Optical Kerr Effect). Measurement by MOKE is a measurement method that uses the magneto-optical effect (magnetic Kerr effect) in which linearly polarized light is incident on the measurement object and the polarization direction rotates.

[0070] Next, a method for manufacturing the domain wall motion element 100 will be described. The domain wall motion element 100 is formed by a lamination process of each layer and a processing process of processing a part of each layer into a predetermined shape. The lamination of each layer can be performed using a sputtering method, a chemical vapor deposition (CVD) method, an electron beam deposition method (EB deposition method), an atomic laser deposition method, or the like. The processing of each layer can be performed using photolithography and etching (for example, Ar etching), or the like.

[0071] First, a reference layer, a non-magnetic layer, a laminate, and a magnetization fixed layer are laminated in this order on the electrode E and the insulating layer In. The laminate is laminated in the order of a ferromagnetic layer and an insertion layer, starting from the side closer to the electrode E. Next, unnecessary parts of these layers in the x direction and y direction are removed by, for example, photolithography and etching. After the unnecessary parts are removed, each layer is processed into a predetermined shape, and the reference layer becomes the reference layer 30, the non-magnetic layer becomes the non-magnetic layer 20, and the laminate becomes the domain wall displacement layer 10. Next, unnecessary parts of the magnetization fixed layer are removed except for two parts of the magnetization fixed layer that overlap the ends of the domain wall displacement layer 10. In this process, the magnetization fixed layer becomes a first magnetization fixed layer 50 and a second magnetization fixed layer 60.

[0072] Next, an insulating layer In is laminated on the domain wall motion layer 10, the first magnetization pinned layer 50, and the second magnetization pinned layer 60. After that, holes are formed in the insulating layer In at positions where the insulating layer In overlaps with the first magnetization pinned layer 50 and the second magnetization pinned layer 60, and the holes are filled with a conductor to obtain the first conductive layer 71 and the second conductive layer 72. Through the above procedure, the domain wall motion element 100 is obtained.

[0073] The domain wall motion element 100 according to the first embodiment has multiple ferromagnetic layers 11 containing Co and Fe sandwiching an insertion layer 12. The magnetization of the ferromagnetic layer 11 exhibits strong perpendicular magnetic anisotropy due to the effect of the interface with the insertion layer 12 (interface perpendicular magnetic anisotropy) and the magnetic coupling between the ferromagnetic layers 11 sandwiching the insertion layer 12. Therefore, the domain wall motion element 100 exhibits a high MR ratio and is excellent in controllability of the domain wall DW.

[0074] In contrast, for example, if the insertion layer 12 is removed from the domain wall displacement layer 10, the thickness of the ferromagnetic layer 11 increases, and the ferromagnetic layer 11 no longer exhibits sufficient perpendicular magnetic anisotropy. If the thickness of the domain wall displacement layer 10 excluding the insertion layer 12 (i.e., the single-layer ferromagnetic layer 11) is reduced in order to maintain the perpendicular magnetic anisotropy, the resistance value of the domain wall displacement layer 10 increases. As a result, part of the current flowing in the x direction along the domain wall displacement layer 10 leaks to the reference layer 30 side via the nonmagnetic layer 20, and the controllability of the domain wall DW decreases.

[0075] In addition, in the domain wall motion element 100, the reference layer 30 is closer to the substrate Sub than the domain wall motion layer 10. The further away from the substrate the laminated film is, the less flat the film becomes, and the less stable the magnetization of the magnetic film formed on the laminated film becomes. The reference layer 30 is a layer that serves as a reference for magnetoresistance change, and increasing the stability of the magnetization of the reference layer 30 increases the MR ratio of the domain wall motion element 100.

[0076] The domain wall motion element 100 is fabricated by building up from a substrate Sub. The insertion layer 12 is made of a material different from that of the ferromagnetic layer 11 and functions as an etching stopper during fabrication to prevent damage to the ferromagnetic layer 11. As a result, it is possible to prevent the MR ratio of the domain wall motion layer 10 from decreasing due to damage caused by etching. The insertion layer 12 also prevents element diffusion when the domain wall motion element 100 is heat-treated, preventing a decrease in the MR ratio of the domain wall motion element 100.

[0077] "Second embodiment" 5 is a cross-sectional view of the domain wall motion element 101 according to the second embodiment cut in an xz plane passing through the center in the y direction of the domain wall motion layer 10. The domain wall motion element 101 according to the second embodiment differs from the domain wall motion element 100 according to the first embodiment in the configurations of the first magnetization pinned layer 55 and the second magnetization pinned layer 65. In the second embodiment, the same configurations as in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0078] The first magnetization fixed layer 55 has a magnetic coupling layer 51 and a ferromagnetic layer 52. The magnetic coupling layer 51 and the ferromagnetic layer 52 are alternately stacked. The second magnetization fixed layer 65 has a magnetic coupling layer 61 and a ferromagnetic layer 62. The magnetic coupling layer 61 and the ferromagnetic layer 62 are alternately stacked.

[0079] The ferromagnetic layer 52 and the ferromagnetic layer 62 may each be made of the same material as the reference layer 30. The magnetic coupling layer 51 and the magnetic coupling layer 61 are nonmagnetic layers. The magnetic coupling layer 51 and the magnetic coupling layer 61 are made of, for example, Ru, Ir, or Rh. The adjacent ferromagnetic layers 52 and the adjacent ferromagnetic layers 62 are magnetically coupled to each other antiferromagnetically.

[0080] The first magnetization pinned layer 55 and the second magnetization pinned layer 65 have different thicknesses. For example, the first magnetization pinned layer 55 and the second magnetization pinned layer 65 have different thicknesses due to the difference in the number of layers that constitute them. For example, the number of layers of the ferromagnetic layer 52 included in the first magnetization pinned layer 55 is different from the number of layers of the ferromagnetic layer 62 included in the second magnetization pinned layer 65. For example, the number of layers of the ferromagnetic layer 52 included in the first magnetization pinned layer 55 is two layers, and the number of layers of the ferromagnetic layer 62 included in the second magnetization pinned layer 65 is one layer.

[0081] The domain wall motion element 101 according to the second embodiment has the same effects as the domain wall motion element 100.

[0082] Moreover, in the domain wall motion element 101 according to the second embodiment, the magnetization orientation directions of the first region A1 and the second region A2 can be easily reversed by simply applying an external magnetic field in one direction. The first magnetization pinned layer 55 and the second magnetization pinned layer 65 have different thicknesses and different saturation magnetization amounts. By utilizing this difference in saturation magnetization amount, the magnetization orientation direction of the first magnetization pinned layer 55 and the magnetization orientation direction of the second magnetization pinned layer 65 can be reversed, and the magnetization orientation directions of the first region A1 and the second region A2 become opposite.

[0083] "Third embodiment" 6 is a cross-sectional view of the domain wall motion element 102 according to the third embodiment cut in the xz plane passing through the center in the y direction of the domain wall motion layer 10. The domain wall motion element 102 according to the third embodiment differs from the domain wall motion element 101 according to the second embodiment in the configurations of the first magnetization pinned layer 56 and the second magnetization pinned layer 66. In the third embodiment, the same configurations as in the second embodiment are denoted by the same reference numerals and will not be described.

[0084] The first magnetization pinned layer 56 has a stacking order of the magnetic coupling layer 51 and the ferromagnetic layer 52 different from that of the first magnetization pinned layer 55 according to the second embodiment. The second magnetization pinned layer 66 has a stacking order of the magnetic coupling layer 61 and the ferromagnetic layer 62 different from that of the second magnetization pinned layer 65 according to the second embodiment. The ferromagnetic layer 52 of the first magnetization pinned layer 56 closest to the substrate Sub is in direct contact with the ferromagnetic layer 11 of the domain wall displacement layer 10. The ferromagnetic layer 62 of the second magnetization pinned layer 66 closest to the substrate Sub is in direct contact with the ferromagnetic layer 11 of the domain wall displacement layer 10.

[0085] The domain wall motion element 102 according to the third embodiment has the same effect as the domain wall motion element 101. In addition, the ferromagnetic layer 11 of the domain wall motion layer 10 and the ferromagnetic layers 52, 62 of the first magnetization pinned layer 56 and the second magnetization pinned layer 66 are in direct contact with each other, thereby strengthening the magnetic connection between the domain wall motion layer 10 and the first magnetization pinned layer 56 and the second magnetization pinned layer 66. As a result, the magnetizations of the first region A1 and the second region A2 are strongly pinned, and it is possible to prevent the domain wall DW from penetrating into the first region A1 or the second region A2.

[0086] "Fourth embodiment" 7 is a cross-sectional view of the domain wall motion element 103 according to the fourth embodiment cut in an xz plane passing through the center in the y direction of the domain wall motion layer 13. The domain wall motion element 103 according to the fourth embodiment differs from the domain wall motion element 102 according to the third embodiment in the configuration of the domain wall motion layer 13. In the fourth embodiment, the same components as those in the third embodiment are denoted by the same reference numerals and will not be described.

[0087] The domain wall displacement layer 13 includes a ferromagnetic layer 11 and an insertion layer 12. The ferromagnetic layers 11 and the insertion layers 12 are alternately stacked. Of the ferromagnetic layers 11 included in the domain wall displacement layer 13, a first ferromagnetic layer 11A that is closest to the nonmagnetic layer 20 is thicker than the other ferromagnetic layers 11 included in the domain wall displacement layer 13.

[0088] The domain wall motion element 103 according to the fourth embodiment has the same effects as the domain wall motion element 102 .

[0089] As described above, since the domain wall motion element 103 is processed from above, the closer it is to the substrate Sub, the less likely it is to be damaged. By increasing the thickness of the first ferromagnetic layer 11A on the side closer to the substrate Sub, the controllability of the domain wall DW of the domain wall motion element 103 is improved. In addition, since the insertion layer 12 also functions as an etching stopper, by increasing the amount of the insertion layer 12 above the domain wall motion layer 13, processing damage to the domain wall motion element 103 can be further suppressed.

[0090] "Fifth embodiment" 8 is a cross-sectional view of the domain wall motion element 104 according to the fifth embodiment cut in an xz plane passing through the center in the y direction of the domain wall motion layer 10. The domain wall motion element 104 according to the fifth embodiment differs from the domain wall motion element 100 according to the first embodiment in the configurations of the first magnetization pinned layer 57 and the second magnetization pinned layer 67. In the fifth embodiment, the same configurations as in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0091] A portion of the first magnetization pinned layer 57 is inserted into the domain wall motion layer 10. A bottom surface 57b of the first magnetization pinned layer 57 is lower than a top surface 10a of the third region A3 of the domain wall motion layer 10. The first magnetization pinned layer 57 is obtained by stacking an insulating layer In on the domain wall motion layer 10, forming a groove in the insulating layer In, and stacking ferromagnetic layers 53 and magnetic coupling layers 54 alternately in the groove. The first magnetization pinned layer 57 has ferromagnetic layers 53 and magnetic coupling layers 54 alternately.

[0092] A portion of the second magnetization pinned layer 67 is inserted into the domain wall motion layer 10. A bottom surface 67b of the second magnetization pinned layer 67 is lower than a top surface 10a of the third region A3 of the domain wall motion layer 10. The second magnetization pinned layer 67 is obtained by stacking an insulating layer In on the domain wall motion layer 10, forming a groove in the insulating layer In, and stacking ferromagnetic layers 63 and magnetic coupling layers 64 alternately in the groove. The second magnetization pinned layer 67 has ferromagnetic layers 63 and magnetic coupling layers 64 alternately.

[0093] The top surface 57a of the first magnetization pinned layer 57 and the top surface 67a of the second magnetization pinned layer 67 are recessed in the z direction according to the shape of the groove. The first conductive layer 73 fits into the recess of the top surface 57a. The second conductive layer 74 fits into the recess of the top surface 67a.

[0094] The ferromagnetic layers 53 and 63 are made of the same material as the ferromagnetic layers 52 and 62. The magnetic coupling layers 54 and 64 are made of the same material as the magnetic coupling layers 51 and 61.

[0095] The domain wall motion element 104 according to the fifth embodiment has the same effects as the domain wall motion element 100.

[0096] In the domain wall motion element 104 according to the fifth embodiment, the first magnetization pinned layer 57 and the second magnetization pinned layer 67 are partially embedded in the domain wall motion layer 10. Therefore, the magnetic connection between the domain wall motion layer 10 and the first magnetization pinned layer 57 and the second magnetization pinned layer 67 is strong, and the magnetization is strongly pinned.

[0097] Sixth embodiment 9 is a cross-sectional view of the domain wall motion element 105 according to the sixth embodiment cut in an xz plane passing through the center in the y direction of the domain wall motion layer 10. The domain wall motion element 105 according to the sixth embodiment differs from the domain wall motion element 100 according to the first embodiment in that it further includes a perpendicular magnetic induction layer 80. In the sixth embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and will not be described.

[0098] The perpendicular magnetic induction layer 80 is on the domain wall displacement layer 10. The perpendicular magnetic induction layer 80 is on, for example, the third region A3 of the domain wall displacement layer 10. The perpendicular magnetic induction layer 80 strengthens the perpendicular magnetic anisotropy of the ferromagnetic layer 11 of the domain wall displacement layer 10. The perpendicular magnetic induction layer 80 includes, for example, any one selected from the group consisting of MgO, Mg-Al-O, Mg, W, Mo, Ta, Pd, and Pt.

[0099] The domain wall motion device 105 according to the sixth embodiment has the same effects as the domain wall motion device 100. In addition, the perpendicular magnetic induction layer 80 enhances the perpendicular magnetic anisotropy of the ferromagnetic layer 11, and the stability of the domain wall motion device 105 against external disturbances becomes higher.

[0100] 10 is a cross-sectional view of a modified example of the domain wall motion element according to the sixth embodiment. The domain wall motion element 105A shown in FIG. 10 differs from the domain wall motion element 105 shown in FIG. 9 in that the perpendicular magnetic induction layer 81 extends between the first magnetization pinned layer 50 and the domain wall motion layer 10 and between the second magnetization pinned layer 60 and the domain wall motion layer 10.

[0101] The perpendicular magnetic induction layer 81 is at least one of between the first magnetization pinned layer 50 and the domain wall movement layer 10 and between the second magnetization pinned layer 60 and the domain wall movement layer 10. When the perpendicular magnetic induction layer 81 is between the first magnetization pinned layer 50 or the second magnetization pinned layer 60 and the domain wall movement layer 10, the magnetization stability of the first region A1 and the second region A2 is increased, and the domain wall DW to the first region A1 and the second region A2 can be suppressed. The thickness of the part of the perpendicular magnetic induction layer 81 inserted between the first magnetization pinned layer 50 and the domain wall movement layer 10 or between the second magnetization pinned layer 60 and the domain wall movement layer 10 is preferably thicker than the thickness of the insertion layer 12 within a range in which the ferromagnetic coupling between the domain wall movement layer 10 and the first magnetization pinned layer 50 or between the domain wall movement layer 10 and the second magnetization pinned layer 60 can be maintained. The thickness of the perpendicular magnetic induction layer 81 other than the portions inserted between the above may be thinner than the thickness of the portions inserted between them.

[0102] Seventh embodiment 11 is a cross-sectional view of the domain wall motion element 106 according to the seventh embodiment cut in an xz plane passing through the center in the y direction of the domain wall motion layer 14. The domain wall motion element 106 according to the seventh embodiment differs from the domain wall motion element 102 according to the third embodiment in the configuration of the domain wall motion layer 14. In the seventh embodiment, the same components as those in the third embodiment are denoted by the same reference numerals and will not be described.

[0103] The domain wall displacement layer 14 has a ferromagnetic layer 11 and an insertion layer 12. The ferromagnetic layer 11 and the insertion layer 12 are alternately stacked. Of the insertion layers 12 included in the domain wall displacement layer 13, the second insertion layer 12B which is the furthest from the nonmagnetic layer 20 is thicker than the other insertion layers 12 included in the domain wall displacement layer 13.

[0104] The domain wall motion element 106 according to the seventh embodiment has the same effects as the domain wall motion element 102 .

[0105] As described above, since the domain wall motion element 106 is processed from above, the possibility of damage is reduced closer to the substrate Sub. By increasing the thickness of the insertion layer 12 at a position away from the substrate Sub, processing damage to the domain wall motion element 106 (particularly damage to the ferromagnetic layer 11, which has a large effect on the MR ratio) can be further suppressed.

[0106] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to these embodiments. For example, the characteristic configurations of the respective embodiments may be combined, or parts of the invention may be modified without departing from the spirit of the invention. [Explanation of symbols]

[0107] 10, 13, 14... domain wall displacement layer, 10a, 57a, 67a... upper surface, 11, 52, 53, 62, 63... ferromagnetic layer, 11A... first ferromagnetic layer, 12... insertion layer, 12A... first insertion layer, 20... non-magnetic layer, 30... reference layer, 40... magnetoresistance effect element, 50, 55, 56, 57... first magnetization fixed layer, 51, 54, 61, 64... magnetic coupling layer, 57b, 67b ...lower surface, 60, 65, 66, 67...second magnetization fixed layer, 71, 73...first conductive layer, 72, 74...second conductive layer, 80, 81...vertical magnetic induction layer, 100, 101, 102, 103, 104, 105...domain wall motion element, 200...magnetic array, A1...first region, A2...second region, A3...third region, A3a...first magnetic domain, A3b...second magnetic domain, In...insulating layer

Claims

1. A magnetoresistance effect element having a reference layer, a nonmagnetic layer, and a domain wall displacement layer, in that order from the side closest to the substrate; a first magnetization pinned layer and a second magnetization pinned layer each in contact with the domain wall displacement layer and spaced apart from each other; The magnetic domain wall displacement layer includes a ferromagnetic layer including a plurality of insertion layers, the ferromagnetic layer contains Co and Fe and has perpendicular magnetic anisotropy; Each of the plurality of insertion layers has an alloy region containing Co and Fe and a plurality of insertion regions dispersed in an island shape, The domain wall motion element, in which a write current is caused to flow between the first magnetization fixed layer and the second magnetization fixed layer along the domain wall motion layer during writing.

2. A magnetoresistive effect element having, in order from the side closest to the substrate, a reference layer, a nonmagnetic layer, and a domain wall displacement layer; a first magnetization pinned layer and a second magnetization pinned layer each in contact with the domain wall displacement layer and spaced apart from each other; The magnetic domain wall displacement layer includes a ferromagnetic layer including a plurality of insertion layers, a lower surface of the first magnetization fixed layer and a lower surface of the second magnetization fixed layer are located below an upper surface of the domain wall displacement layer, the ferromagnetic layer contains Co and Fe and has perpendicular magnetic anisotropy; The domain wall motion element, in which a write current is caused to flow between the first magnetization fixed layer and the second magnetization fixed layer along the domain wall motion layer during writing.

3. A magnetoresistive effect element having, in order from the side closest to the substrate, a reference layer, a nonmagnetic layer, and a domain wall displacement layer; a first magnetization pinned layer and a second magnetization pinned layer each in contact with the domain wall displacement layer and spaced apart from each other; The magnetic domain wall displacement layer includes a ferromagnetic layer including a plurality of insertion layers, the ferromagnetic layer contains Co and Fe and has perpendicular magnetic anisotropy; a first conductive layer in contact with the first magnetization fixed layer and a second conductive layer in contact with the second magnetization fixed layer, the first conductive layer fits into a recess formed in an upper surface of the first magnetization fixed layer; The domain wall motion element, in which a write current is caused to flow between the first magnetization fixed layer and the second magnetization fixed layer along the domain wall motion layer during writing.

4. 4. The domain wall motion element according to claim 1, wherein the first magnetization pinned layer and the second magnetization pinned layer have different thicknesses.

5. each of the first magnetization pinned layer and the second magnetization pinned layer includes a magnetic coupling layer and a ferromagnetic layer that are alternately stacked; 5. The domain wall motion element according to claim 1, wherein the number of ferromagnetic layers included in said first magnetization fixed layer is different from the number of ferromagnetic layers included in said second magnetization fixed layer.

6. 6. The domain wall motion element according to claim 1, wherein the insertion layer contains any one selected from the group consisting of MgO, Mg--Al--O, Mg, W, Mo, Ta, Pd, and Pt.

7. a first insertion layer, which is the closest to the nonmagnetic layer, of the insertion layers includes any one selected from the group consisting of W, Mo, Ta, Pd, and Pt; 7. The domain wall motion element according to claim 1, wherein any one of the insertion layers other than the first insertion layer contains MgO or Mg--Al--O.

8. A domain wall motion element according to any one of claims 1 to 7, wherein a first ferromagnetic layer among the ferromagnetic layers included in the domain wall motion layer, which is closest to the non-magnetic layer, is thicker than the other ferromagnetic layers included in the domain wall motion layer.

9. The domain wall motion element according to any one of claims 1 to 8, wherein the insertion layer included in the domain wall motion layer that is farthest from the non-magnetic layer is thicker than the other insertion layers included in the domain wall motion layer.

10. Further comprising a perpendicular magnetic induction layer; 10. The domain wall motion element according to claim 1, wherein the perpendicular magnetic induction layer is on the domain wall motion layer.

11. 11. The domain wall motion element according to claim 10, wherein the perpendicular magnetic induction layer includes any one selected from the group consisting of MgO, Mg-Al-O, Mg, W, Mo, Ta, Pd, and Pt.

12. The domain wall motion element according to claim 10 or 11, wherein the perpendicular magnetic induction layer is located at least either between the first magnetization fixed layer and the domain wall motion layer or between the second magnetization fixed layer and the domain wall motion layer.

13. A magnetic array comprising a plurality of domain wall motion elements according to any one of claims 1 to 12.

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