JP7586745B2 - Domain wall motion element and magnetic recording array - Google Patents

Description

The present invention relates to a domain wall motion element and a magnetic recording array.

Attention is being focused on next-generation non-volatile memory to replace flash memory and other memory devices, which are reaching the limits of miniaturization. For example, MRAM (Magnetoresistive Random Access Memory), ReRAM (Resistance Random Access Memory), and PCRAM (Phase Change Random Access Memory) are known as next-generation non-volatile memories.

MRAM uses the change in resistance caused by a change in the direction of magnetization to record data. Data recording is performed by each of the magnetoresistance change elements that make up the MRAM. For example, Patent Document 1 describes a three-terminal magnetoresistance effect element that separates the paths of the write current and the read current.

Patent No. 6275806

When miniaturizing a magnetoresistance effect element, a process called slimming may be performed. Slimming is a process in which an ion beam is irradiated onto the side of the magnetoresistance effect element to reduce the area of the magnetoresistance effect element in plan view. However, when an ion beam is irradiated onto an exposed metal surface, some of the metal may scatter and re-adhere to the side wall of the magnetoresistance effect element. Impurities that adhere to the side wall of the magnetoresistance effect element deteriorate the magnetic properties of the ferromagnetic material that constitutes the magnetoresistance effect element. The attached impurities may also cause leakage from the magnetoresistance effect element. Impurities that adhere to the side wall of the magnetoresistance effect element reduce the reliability of the magnetoresistance effect element.

The present invention was made in consideration of the above problems, and provides a highly reliable magnetoresistance effect element and magnetic recording array.

(1) The domain wall motion element according to the first aspect is stacked in the order of a first ferromagnetic layer, a nonmagnetic layer, and a second ferromagnetic layer from the side closest to the substrate, and in a cross section cut along a second direction perpendicular to the first direction in which the first ferromagnetic layer extends when viewed in a plan view from the stacking direction, the shortest width of the first ferromagnetic layer in the second direction is shorter than the width of the nonmagnetic layer in the second direction.

(2) In a cut surface along the stacking direction and the second direction of the domain wall motion element according to the above aspect, the side surface of the first ferromagnetic layer may be inclined with respect to the stacking direction.

(3) In a cut surface along the stacking direction and the second direction of the domain wall motion element according to the above aspect, the side of the first ferromagnetic layer has a first inclined surface and a second inclined surface, the first inclined surface inclining from a lower end of the first ferromagnetic layer on a side closer to the substrate toward the center of the first ferromagnetic layer in the second direction, and the second inclined surface inclining from an upper end of the first ferromagnetic layer on a side farther from the substrate toward the center of the first ferromagnetic layer in the second direction.

(4) In the domain wall motion element according to the above aspect, the width in the second direction of the first surface of the first ferromagnetic layer on the side of the nonmagnetic layer may be shorter than the width in the second direction of the nonmagnetic layer.

(5) In the domain wall motion element according to the above aspect, the position at which the width of the first ferromagnetic layer in the second direction is shortest may be located on the nonmagnetic layer side from the center of the first ferromagnetic layer in the stacking direction.

(6) In the domain wall motion element according to the above aspect, the maximum width of the first ferromagnetic layer in the second direction may be shorter than the width of the nonmagnetic layer in the second direction.

(7) In the domain wall motion element according to the above aspect, the width in the second direction of the second surface of the first ferromagnetic layer on the side farther from the nonmagnetic layer may be longer than the width in the second direction of the nonmagnetic layer.

(8) In the domain wall motion element according to the above aspect, the thickness of the nonmagnetic layer may be 30 Å or more.

(9) In the domain wall motion element according to the above aspect, the milling rate of the nonmagnetic layer may be slower than the milling rate of the first ferromagnetic layer.

(10) The domain wall motion element according to the above aspect may further include an underlayer on the opposite side of the first ferromagnetic layer to the nonmagnetic layer, and the underlayer may have a slower milling rate than the first ferromagnetic layer.

(11) The first ferromagnetic layer of the domain wall motion element according to the above aspect may contain an element constituting the underlayer, and the abundance ratio of the element may be higher in a first region located closer to the underlayer than a position where the width of the first ferromagnetic layer in the second direction is shortest in the stacking direction, than in a second region located closer to the non-magnetic layer than a position where the width of the first ferromagnetic layer in the second direction is shortest in the stacking direction.

(12) The domain wall motion element according to the above aspect has a first conductive part and a second conductive part sandwiching the nonmagnetic layer in the first direction and electrically connected to the first ferromagnetic layer via the underlayer, and the width of each of the first conductive part and the second conductive part in the second direction may be wider than the width of the first ferromagnetic layer in the second direction, and the milling rate of the underlayer may be slower than the milling rate of the first conductive part and the second conductive part.

(13) The domain wall motion element according to the above aspect may further include a metal layer different from the second ferromagnetic layer on the side of the second ferromagnetic layer in the second direction.

(14) The magnetic recording array according to the second aspect has a plurality of domain wall motion elements according to the above aspect.

The domain wall motion element and magnetic recording array according to the above aspect have excellent reliability.

1 is a configuration diagram of a magnetic recording array according to a first embodiment. 3 is a cross-sectional view of a characteristic portion of the magnetic recording array according to the first embodiment. 2 is an xz cross-sectional view of the domain wall motion element according to the first embodiment; FIG. FIG. 2 is a plan view of the domain wall motion element according to the first embodiment. 3 is a yz cross-sectional view at the center in the x direction of the domain wall motion element according to the first embodiment. FIG. 4 is a yz cross-sectional view of the first conductive part of the domain wall motion element according to the first embodiment. FIG. 5A to 5C are schematic diagrams for explaining slimming that occurs when the domain wall motion element according to the first embodiment is fabricated. 11 is a yz cross-sectional view at the center in the x direction of a domain wall motion element according to a first modified example. FIG. FIG. 13 is a yz cross-sectional view at the center in the x direction of a domain wall motion element according to a second modified example. FIG. 13 is a yz cross-sectional view at the center in the x direction of a domain wall motion element according to a third modified example. 2 is an xz cross-sectional view of the domain wall motion element according to the first embodiment; FIG. 3 is a yz cross-sectional view at the center in the x direction of the domain wall motion element according to the first embodiment. FIG.

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 to them. Appropriate changes can be made within the scope of the effects of the present invention.

First, the directions are defined. The x-direction and 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 first ferromagnetic layer 10 described later extends, and is the direction from the first conductive part 51 to the second conductive part 52 described later. The y-direction is a direction perpendicular to the x-direction. The z-direction is the direction from the substrate Sub described later to the domain wall motion element 100. The z-direction is an example of a stacking direction. 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.

[First embodiment]
1 is a configuration diagram of a magnetic recording array according to the first embodiment. The magnetic recording array 200 includes a plurality of domain wall motion elements 100, a plurality of first wirings Wp1 to Wpn, a plurality of second wirings Cm1 to Cmn, a plurality of third wirings Rp1 to Rpn, a plurality of first switching elements 110, a plurality of second switching elements 120, and a plurality of third switching elements 130. The magnetic recording array 200 can be used, for example, in a magnetic memory, a product-sum calculator, or a neuromorphic device.

<First wiring, second wiring, third wiring>
The first wirings Wp1 to Wpn are write wirings. The first wirings Wp1 to Wpn electrically connect a power source to one or more domain wall motion elements 100. The power source is connected to one end of the magnetic recording array 200 during use. is connected to.

The second wirings Cm1 to Cmn are common wirings. The common wirings are wirings that can be used both when writing and reading data. The second wirings Cm1 to Cmn electrically connect a reference potential to one or more domain wall motion elements 100. The reference potential is, for example, ground. The second wirings Cm1 to Cmn 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.

The third wirings Rp1 to Rpn are read wirings. The third wirings Rp1 to Rpn electrically connect a power source to one or more domain wall motion elements 100. The power source is connected to one end of the magnetic recording array 200 during use.

<First Switching Element, Second Switching Element, Third Switching Element>
1 are connected to the multiple domain wall motion elements 100, respectively. The first switching element 110 is connected between each of the domain wall motion elements 100 and the first wirings Wp1 to Wpn. The second switching element 120 is connected between each of the domain wall motion elements 100 and the second wirings Cm1 to Cmn. The third switching element 130 is connected between each of the domain wall motion elements 100 and the third wirings Rp1 to Rpn.

When the first switching element 110 and the second switching element 120 are turned ON, a write current flows between the first wiring Wp1-Wpn and the second wiring Cm1-Cmn connected to a specific domain wall motion element 100. When the first switching element 110 and the third switching element 130 are turned ON, a read current flows between the second wiring Cm1-Cmn and the third wiring Rp1-Rpn connected to a specific domain wall motion element 100.

The first switching element 110, the second switching element 120, and the third switching element 130 are elements that control the flow of current. The first switching element 110, the second switching element 120, and the third switching element 130 are, for example, elements that use a phase change of a crystal layer such as a transistor or an Ovonic Threshold Switch (OTS), elements that use a change in band structure such as a Metal-Insulator Transition (MIT) switch, elements that use a breakdown voltage such as a Zener diode and an avalanche diode, and elements whose conductivity changes with a change in atomic position.

Any of the first switching element 110, the second switching element 120, and the third switching element 130 may be shared by the domain wall motion elements 100 connected to the same wiring. For example, when the first switching element 110 is shared, one first switching element 110 is provided upstream of the first wiring Wp1 to Wpn. For example, when the second switching element 120 is shared, one second switching element 120 is provided upstream of the second wiring Cm1 to Cmn. For example, when the third switching element 130 is shared, one third switching element 130 is provided upstream of the third wiring Rp1 to Rpn.

Figure 2 is a cross-sectional view of a characteristic portion of the magnetic recording array 200 according to the first embodiment. Figure 2 is a cross-section of one domain wall motion element 100 in Figure 1 cut along the xz plane passing through the center of the width of the first ferromagnetic layer 10 in the y direction.

The first switching element 110 and the second switching element 120 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 130 is electrically connected to the electrode E and is located, for example, in the depth direction (+y direction) of the paper.

Each of the transistors Tr and the domain wall motion element 100 are electrically connected via wiring W. The wiring W includes a conductive material. The wiring W extends, for example, in the z direction. The wiring W is, for example, a via wiring formed in an opening of the insulating layer In.

The domain wall motion element 100 and the transistor Tr are electrically isolated by an insulating layer In, except for the wiring W. The insulating layer In is an insulating layer that insulates between the wirings of the multilayer wiring and between the elements. The insulating layer In is, for example, silicon oxide (SiO _x ), silicon nitride (SiN _x ), silicon carbide (SiC), chromium nitride, silicon carbonitride (SiCN), silicon oxynitride (SiON), aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO _x ), or the like.

"Magnetic domain wall motion element"
3 is a cross-sectional view of the domain wall motion element 100 cut in an xz plane passing through the center of the first ferromagnetic layer 10 in the y direction. FIG. 4 is a plan view of the domain wall motion element 100 from the z direction. FIG. 5 is a cross-sectional view of the domain wall motion element 100 cut in a yz plane passing through the center of the domain wall motion element 100 in the x direction. FIG. 5 is a cross-sectional view of the domain wall motion element 100 cut along line A-A in FIG. 4. FIG. 6 is a cross-sectional view of the domain wall motion element 100 cut in a yz plane passing through the first conductive part 51. FIG. 6 is a cross-sectional view of the domain wall motion element 100 cut along line B-B in FIG. 4.

The domain wall motion element 100 has, for example, a first ferromagnetic layer 10, a second ferromagnetic layer 20, a non-magnetic layer 30, an underlayer 40, a first conductive portion 51, and a second conductive portion 52. For example, the first ferromagnetic layer 10, the non-magnetic layer 30, and the second ferromagnetic layer 20 are stacked in this order from the side closer to the substrate Sub. Other layers may be inserted between the first ferromagnetic layer 10 and the non-magnetic layer 30 and between the non-magnetic layer 30 and the second ferromagnetic layer 20. When writing data to the domain wall motion element 100, a write current is passed through the first ferromagnetic layer 10 between the first conductive portion 51 and the second conductive portion 52. When reading data from the domain wall motion element 100, a read current is passed between the first conductive portion 51 or the second conductive portion 52 and the second ferromagnetic layer 20.

"First ferromagnetic layer"
The first ferromagnetic layer 10 extends in the x-direction. A write current is passed through the first ferromagnetic layer 10. The first ferromagnetic layer 10 is, for example, a rectangle with its major axis in the x-direction and its minor axis in the y-direction when viewed in a plan view from the z-direction. The first ferromagnetic layer 10 is, for example, closer to the substrate Sub than the second ferromagnetic layer 20. The write current flows along the first ferromagnetic layer 10 from the first conductive portion 51 to the second conductive portion 52, or from the second conductive portion 52 to the first conductive portion 51.

The first ferromagnetic layer 10 is a layer capable of magnetically recording information by changing the internal magnetic state. The first ferromagnetic layer 10 is sometimes called a magnetic recording layer or a domain wall displacement layer.

As shown in FIG. 3, the first ferromagnetic layer 10 has, for example, magnetization fixed regions 11 and 12 and a domain wall motion region 13. The domain wall motion region 13 is sandwiched between the two magnetization fixed regions 11 and 12, for example, in the x direction.

The magnetization fixed region 11 is a region overlapping with the first conductive part 51 of the first ferromagnetic layer 10 when viewed from the z direction. The magnetization fixed region 12 is a region overlapping with the second conductive part 52 of the first ferromagnetic layer 10 when viewed from the z direction. The magnetizations _M11 and M12 of the magnetization fixed regions 11 and ₁₂ are less likely to reverse than the magnetizations _M13A and _M13B of the domain wall motion region 13, and do not reverse even when an external force of a threshold value at which the magnetizations _M13A and _M13B of the domain wall motion region 13 are reversed is applied. Therefore, the magnetizations _M11 and M12 of the magnetization fixed regions 11 and ₁₂ are said to be fixed with respect to the magnetizations _M13A and _M13B of the domain wall motion region 13.

The magnetization _M11 of the magnetization fixed region 11 and the magnetization _M12 of the magnetization fixed region 12 are oriented in different directions. The magnetization _M11 of the magnetization fixed region 11 and the magnetization _M12 of the magnetization fixed region 12 are oriented, for example, in opposite directions. The magnetization _M11 of the magnetization fixed region 11 is oriented, for example, in the +z direction, and the magnetization _M12 of the magnetization fixed region 12 is oriented, for example, in the -z direction.

The domain wall motion region 13 is composed of a first magnetic domain 13A and a second magnetic domain 13B. The first magnetic domain 13A is adjacent to the magnetization fixed region 11. The magnetization _M13A of the first magnetic domain 13A is influenced by the magnetization _M11 of the magnetization fixed region 11 and is oriented in the same direction as the magnetization _M11 of the magnetization fixed region 11, for example. The second magnetic domain 13B is adjacent to the magnetization fixed region 12. The magnetization _M13B of the second magnetic domain 13B is influenced by the magnetization _M12 of the magnetization fixed region 12 and is oriented in the same direction as the magnetization _M12 of the magnetization fixed region 12, for example. Therefore, the magnetization _M13A of the first magnetic domain 13A and the magnetization _M13B of the second magnetic domain 13B are oriented in different directions. The magnetization M _13A of the first magnetic domain 13A and the magnetization M _13B of the second magnetic domain 13B are oriented in, for example, opposite directions.

The boundary between the first magnetic domain 13A and the second magnetic domain 13B is the domain wall DW. The domain wall DW moves within the domain wall motion region 13. In principle, the domain wall DW does not penetrate into the magnetization fixed regions 11 and 12.

In the domain wall motion region 13, the domain wall DW moves by applying a write current in the x direction of the domain wall motion region 13. For example, when a write current (e.g., a current pulse) in the +x direction is applied to the domain wall motion region 13, 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 13A to the second magnetic domain 13B, electrons spin-polarized in the second magnetic domain 13B reverse the magnetization M _{13A of the first magnetic domain 13A. The magnetization reversal of the magnetization M 13A of} the first magnetic domain 13A causes the domain wall DW to move in the -x direction. When the domain wall moves in the domain wall motion region 13, the ratio of the first magnetic domain 13A to the second magnetic domain 13B changes.

In the domain wall motion region 13, when the domain wall DW moves and the ratio between the first magnetic domain 13A and the second magnetic domain 13B changes, the resistance of the domain wall motion element 100 changes according to the ratio between the first magnetic domain 13A and the second magnetic domain 13B. Furthermore, the resistance value of the domain wall motion element 100 changes stepwise when the position of the domain wall DW is moved stepwise, and changes continuously when the position of the domain wall DW is moved continuously. The domain wall motion element 100, whose resistance value changes stepwise, is suitable for handling multi-value data. The domain wall motion element 100, whose resistance value changes continuously, is suitable for handling analog data.

As shown in Figures 5 and 6, the minimum width L10min in the y direction of the first ferromagnetic layer 10 is shorter than the width L30 in the y direction of the nonmagnetic layer 30. The width L30 in the y direction of the nonmagnetic layer 30 is the average value of the width in the y direction, and in the case where the width in the y direction changes depending on the position in the z direction, for example, this means the average value.

The width in the y direction of the first ferromagnetic layer 10 shown in Figures 5 and 6 varies depending on the position in the z direction. For example, the first surface 10a and the second surface 10b of the first ferromagnetic layer 10 have different widths in the y direction. The first surface 10a is the surface of the first ferromagnetic layer 10 facing the nonmagnetic layer 30. The second surface 10b is the surface of the first ferromagnetic layer 10 opposite the first surface 10a.

The width in the y direction of the first surface 10a shown in FIG. 5 and FIG. 6 is the same as the width L30 in the y direction of the nonmagnetic layer 30. The width in the y direction of the first ferromagnetic layer 10 shown in FIG. 5 and FIG. 6 narrows from the first surface 10a toward the second surface 10b, and after reaching the minimum width L10min, it widens. The position of the minimum width L10min is, for example, on the nonmagnetic layer 30 side from the center of the first ferromagnetic layer 10 in the z direction. The width in the y direction of the first ferromagnetic layer 10 shown in FIG. 5 and FIG. 6 is the longest at the second surface 10b. The width in the y direction of the second surface 10b shown in FIG. 5 and FIG. 6 is longer than the width L30 in the y direction of the nonmagnetic layer 30. The maximum width L10max in the y direction of the first ferromagnetic layer 10 is, for example, longer than the width L30 in the y direction of the nonmagnetic layer 30.

The y-direction side surface of the first ferromagnetic layer 10 shown in Figures 5 and 6 is inclined in the y-direction with respect to the z-direction. The y-direction side surface of the first ferromagnetic layer 10 can be divided into a first inclined surface s1 and a second inclined surface s2. The first inclined surface s1 is an inclined surface that inclines toward the center of the first ferromagnetic layer 10 in the y-direction, based on the lower end of the side surface of the first ferromagnetic layer 10 on the substrate Sub side. The second inclined surface s2 is an inclined surface that inclines toward the center of the first ferromagnetic layer 10 in the y-direction, based on the upper end of the side surface of the first ferromagnetic layer 10 on the nonmagnetic layer 30 side. The second inclined surface s2 overhangs the first inclined surface s1.

The first inclined surface s1 and the second inclined surface s2 sandwich an inflection point p1 where the inclination of the tangent of the side surface of the first ferromagnetic layer 10 with respect to the z direction becomes zero. The inflection point p1 is located inside the y direction end of the nonmagnetic layer 30. The y direction side surface of the first ferromagnetic layer 10 is recessed, for example, with respect to a virtual plane lowered in the z direction from the y direction end of the nonmagnetic layer 30.

The first ferromagnetic layer 10 is made of a magnetic material. The first ferromagnetic layer 10 preferably contains at least one element selected from the group consisting of Co, Ni, Fe, Pt, Pd, Gd, Tb, Mn, Ge, and Ga. Examples of materials used for the first ferromagnetic layer 10 include a laminated film of Co and Ni, a laminated film of Co and Pt, a laminated film of Co and Pd, an MnGa-based material, a GdCo-based material, and a TbCo-based material. Ferrimagnetic materials such as MnGa-based materials, GdCo-based materials, and TbCo-based materials have small saturation magnetization, and the threshold current required to move the domain wall DW is small. In addition, the laminated film of Co and Ni, the laminated film of Co and Pt, and the laminated film of Co and Pd have large coercive force, and the movement speed of the domain wall DW is slow.

The first ferromagnetic layer 10 may contain elements that constitute the underlayer 40. The abundance ratio of the elements is, for example, higher in the first region R1, which is closer to the underlayer 40 than the position where the first ferromagnetic layer 10 has the shortest width L10min in the z direction, than in the second region R2, which is closer to the nonmagnetic layer 30 than the position where the first ferromagnetic layer 10 has the shortest width L10min in the z direction.

"Non-magnetic layer"
The nonmagnetic layer 30 is, for example, in contact with the first ferromagnetic layer 10. The nonmagnetic layer 30 is on the first ferromagnetic layer 10. The nonmagnetic layer 30 is between the first ferromagnetic layer 10 and the second ferromagnetic layer 20.

The nonmagnetic layer 30 is made of, for example, a nonmagnetic insulator, semiconductor, or metal. The nonmagnetic insulator is, for example, Al ₂ O ₃ , SiO ₂ , MgO, MgAl ₂ O ₄ , 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 30 is made of a nonmagnetic insulator, the nonmagnetic layer 30 is a tunnel barrier layer. The nonmagnetic metal is, for example, Cu, Au, Ag, or the like. The nonmagnetic semiconductor is, for example, Si, Ge, CuInSe ₂ , CuGaSe ₂ , Cu(In,Ga)Se ₂ , or the like.

The milling rate of the nonmagnetic layer 30 is, for example, slower than that of the first ferromagnetic layer 10. The milling rate is the milling rate for dry etching. For dry etching, for example, ion beam etching is used. For ion beam etching, a rare gas element such as Ar, Kr, or Xe, or ions thereof, accelerated at a voltage of several hundred to several kV, can be used for milling. When the nonmagnetic layer 30 is an oxide, the milling rate is often slower than that of the first ferromagnetic layer 10, which is a metal.

The thickness of the nonmagnetic layer 30 is preferably 20 Å or more, and more preferably 30 Å or more. If the thickness of the nonmagnetic layer 30 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 preferably 1×10 ⁴ Ωμm ² or more, and more preferably 1×10 ⁵ Ωμm ² or more. The resistance area area (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 the cross section obtained by cutting the nonmagnetic layer 30 in the xy plane).

In addition, when the nonmagnetic layer 30 is thick, impurities tend to reattach to the side walls of the nonmagnetic layer 30 due to differences in milling rate with other layers during slimming. By controlling the relationship between the width L30 of the nonmagnetic layer 30 in the y direction and the shortest width L10min in the y direction of the first ferromagnetic layer 10, it is possible to suppress reattachment of impurities to the side walls of the nonmagnetic layer 30 even when the nonmagnetic layer 30 is thick.

"Second ferromagnetic layer"
The second ferromagnetic layer 20 is on the nonmagnetic layer 30. The second ferromagnetic layer 20 has a magnetization _M20 oriented in one direction. The magnetization _M20 of the second ferromagnetic layer 20 is less likely to reverse than the magnetizations _M13A and _M13B of the domain wall motion region 13 when a predetermined external force is applied. The predetermined external force is, for example, an external force applied to the magnetization by an external magnetic field or an external force applied to the magnetization by a spin-polarized current. The second ferromagnetic layer 20 may be called a magnetization fixed layer or a magnetization reference layer.

The resistance value of the domain wall motion element 100 changes depending on the difference in the relative angle between the magnetization of the second ferromagnetic layer 20 and the magnetizations _M13A and _M13B of the domain wall motion region 13. The magnetization _M13A of the first magnetic domain 13A is, for example, in the same direction (parallel) as the magnetization _M20 of the second ferromagnetic layer 20, and the magnetization _M13B of the second magnetic domain 13B is, for example, in the opposite direction (anti-parallel) to the magnetization _M20 of the second ferromagnetic layer 20. When the area of the first magnetic domain 13A in the portion overlapping with the second ferromagnetic layer 20 in a plan view from the z direction becomes larger, the resistance value of the domain wall motion element 100 becomes lower. On the other hand, when the area of the second magnetic domain 13B in the portion overlapping with the second ferromagnetic layer 20 in a plan view from the z direction becomes larger, the resistance value of the domain wall motion element 100 becomes higher.

The second ferromagnetic layer 20 includes a ferromagnetic material. The second ferromagnetic layer 20 includes, for example, a material that is easy to obtain a coherent tunnel effect between the second ferromagnetic layer 20 and the first ferromagnetic layer 10. The second ferromagnetic layer 20 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 one or more of these metals and at least one of the elements B, C, and N, etc. The second ferromagnetic layer 20 is, for example, Co-Fe, Co-Fe-B, or Ni-Fe.

The second ferromagnetic layer 20 may be, for example, a Heusler alloy. The Heusler alloy is a half metal and has a high spin polarization. The Heusler alloy is an intermetallic compound having a chemical composition of XYZ or X ₂ YZ, 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 Co ₂ FeSi, Co ₂ FeGe, Co ₂ FeGa, Co ₂ MnSi, Co ₂ Mn _1-a Fe _a Al _b Si _1-b , and Co ₂ FeGe _1-c Ga _c .

When the magnetization easy axis of the second ferromagnetic layer 20 is in the z direction (a perpendicular magnetization film), the film thickness of the second ferromagnetic layer 20 is preferably 1.5 nm or less, and more preferably 1.0 nm or less. When the film thickness of the second ferromagnetic layer 20 is made thin, perpendicular magnetic anisotropy (interface perpendicular magnetic anisotropy) is added to the second ferromagnetic layer 20 at the interface between the second ferromagnetic layer 20 and another layer (non-magnetic layer 30), and the magnetization of the second ferromagnetic layer 20 is more likely to be oriented in the z direction.

When the magnetization easy axis of the second ferromagnetic layer 20 is in the z direction (a perpendicular magnetization film), the second ferromagnetic layer 20 is preferably a laminate of a ferromagnetic material selected from the group consisting of Co, Fe, and Ni and a non-magnetic material selected from the group consisting of Pt, Pd, Ru, and Rh, and more preferably an intermediate layer selected from the group consisting of Ir and Ru is inserted at any position of the laminate. By stacking a ferromagnetic material and a non-magnetic material, perpendicular magnetic anisotropy can be added, and by inserting an intermediate layer, the magnetization of the second ferromagnetic layer 20 is more likely to be oriented in the z direction.

An antiferromagnetic layer may be provided on the surface of the second ferromagnetic layer 20 opposite the nonmagnetic layer 30, with a spacer layer interposed between them. The second ferromagnetic layer 20, the spacer layer, and the antiferromagnetic layer form a synthetic antiferromagnetic structure (SAF structure). The synthetic antiferromagnetic structure is made of two magnetic layers sandwiching a nonmagnetic layer. The second ferromagnetic layer 20 and the antiferromagnetic layer are antiferromagnetically coupled, so that the coercive force of the second ferromagnetic layer 20 is greater than when there is no antiferromagnetic layer. The antiferromagnetic layer is, for example, IrMn, PtMn, or the like. The spacer layer includes, for example, at least one selected from the group consisting of Ru, Ir, and Rh.

The underlayer 40 is located on the opposite side of the first ferromagnetic layer 10 to the nonmagnetic layer 30. The underlayer 40 may be located only in a position that overlaps with the domain wall motion region 13 in the z direction.

The underlayer 40 is made of a non-magnetic material. The underlayer 40 determines, for example, the crystal structure of the first ferromagnetic layer 10. The crystallinity of the first ferromagnetic layer 10 is increased by the crystal structure of the underlayer 40, and the orientation of the magnetization of the first ferromagnetic layer 10 is increased. The crystal structure of the underlayer 40 is, for example, amorphous, a (001)-oriented NaCl structure, a (002)-oriented perovskite structure represented by the composition formula _ABO3 , or a (001)-oriented tetragonal or cubic structure.

The underlayer 40 is a conductor or an insulator. The underlayer 40 is preferably a conductor. When the underlayer 40 is a conductor, the thickness of the underlayer 40 is preferably thinner than the thickness of the first ferromagnetic layer 10. The underlayer 40 contains, for example, Ta, Ru, Pt, Ir, Rh, W, Pd, Cu, Au, or Cu. The underlayer 40 is, for example, a Ta layer, a Pt layer, or a laminate of a Ta layer and a Pt layer.

The underlayer 40 has a milling rate slower than that of the first ferromagnetic layer 10, for example. The underlayer 40 also has a milling rate slower than that of the first conductive portion 51 and the second conductive portion 52, for example. For example, the above relationship is satisfied when the underlayer 40 contains one or more elements selected from Al, Cr, Mg, Ta, Ti, and W, the first ferromagnetic layer 10 contains one or more elements selected from Co, Fe, Ni, Pt, Pd, Ir, and Rh, and the first conductive portion 51 and the second conductive portion 52 are alloys or laminates containing one or more elements selected from Au, Cu, and Ru. Specifically, for example, the underlayer is a laminate film of Ta or Ta and Pt, the first ferromagnetic layer 10 is a laminate film of Co and Pt, and the first conductive portion 51 and the second conductive portion 52 are Au.

The thickness of the underlayer 40 is, for example, approximately constant in the xy plane. The average thickness of the underlayer 40 is, for example, 50 Å or less. The average thickness is the average value of the thicknesses of the underlayer 40 measured at each of the x-direction positions that divide the underlayer 40 into 10 equally spaced positions in the x direction.

"First conductive portion and second ferromagnetic portion"
The first conductive portion 51 and the second conductive portion 52 are electrically connected to the first ferromagnetic layer 10. The first conductive portion 51 and the second conductive portion 52 are connected via an underlayer 40 as shown in FIG. 6, for example. The first conductive portion 51 and the second conductive portion 52 may be directly connected to the first ferromagnetic layer 10. The first conductive portion 51 is connected to, for example, a first end portion of the first ferromagnetic layer 10, and the second conductive portion 52 is connected to, for example, a second end portion of the first ferromagnetic layer 10. The first conductive portion 51 and the second conductive portion 52 are, for example, connection portions between the wiring W and the first ferromagnetic layer 10.

The first conductive portion 51 and the second conductive portion 52 are columnar bodies. The first conductive portion 51 and the second conductive portion 52 shown in FIG. 4 have a rectangular shape when viewed from the z direction. The first conductive portion 51 and the second conductive portion 52 may have any shape when viewed from the z direction, and may be circular, elliptical, or amorphous. The width of the first conductive portion 51 and the second conductive portion 52 in the y direction is, for example, wider than the width of the first ferromagnetic layer 10 and the nonmagnetic layer 30 in the y direction. The top surfaces of the first conductive portion 51 and the second conductive portion 52 are, for example, etched and recessed with respect to the xy plane.

The first conductive portion 51 and the second conductive portion 52 are made of a material having electrical conductivity. The first conductive portion 51 and the second conductive portion 52 include, for example, a magnetic material. The first conductive portion 51 and the second conductive portion 52 include, 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 elements of B, C, and N, etc. The first conductive portion 51 and the second conductive portion 52 are, for example, Co-Fe, Co-Fe-B, Ni-Fe, etc. In addition, when the magnetization easy axis of the first conductive portion 51 and the second conductive portion 52 is in the z direction (perpendicular magnetization film), it is preferable that the first conductive portion 51 and the second conductive portion 52 are a laminate of a ferromagnetic material selected from the group consisting of Co, Fe, and Ni and a non-magnetic material selected from the group consisting of Pt, Pd, Ru, and Rh. The first conductive portion 51 and the second conductive portion 52 may also be a synthetic antiferromagnetic structure (SAF structure). A synthetic antiferromagnetic structure consists of two magnetic layers sandwiching a nonmagnetic layer. The magnetization of each of the two magnetic layers is fixed, and the directions of the fixed magnetization are opposite to each other.

When the first conductive unit 51 includes a magnetic material, the magnetization _M51 of the first conductive unit 51 is oriented in one direction. For example, the magnetization _M51 is oriented in the +z direction. The first conductive unit 51 fixes the magnetization _M11 of the magnetization fixed region 11. The magnetization _M51 of the first conductive unit 51 and the magnetization _M11 of the magnetization fixed region 11 are oriented in the same direction, for example.

When the second conductive unit 52 includes a magnetic material, the magnetization _M52 of the second conductive unit 52 is oriented in a different direction from the magnetization _M51 of the first conductive unit 51. The magnetization _M52 is oriented in the -z direction, for example. In this case, the second conductive unit 52 fixes the magnetization _M12 of the magnetization fixed region 12, and the magnetization _M52 of the second conductive unit 52 and the magnetization _M12 of the magnetization fixed region 12 are oriented in the same direction, for example.

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

Next, a method for manufacturing the magnetic recording array 200 will be described. The magnetic recording array 200 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 evaporation method (EB evaporation method), an atomic laser deposition method, or the like. The processing of each layer can be performed using photolithography, or the like.

First, impurities are doped into predetermined positions of the substrate Sub to form a source region S and a drain region D. Next, a gate insulating film GI and a gate electrode G are formed between the source region S and the drain region D. The source region S, the drain region D, the gate insulating film GI, and the gate electrode G form the transistor Tr.

Next, an insulating layer In is formed to cover the transistor Tr. An opening is formed in the insulating layer In and the opening is filled with a conductor to form the wiring W. The first wiring Wp and the second wiring Cm are formed by stacking the insulating layer In to a predetermined thickness, forming a groove in the insulating layer In, and filling the groove with a conductor.

The first conductive portion 51 and the second conductive portion 52 can be formed, for example, by stacking a ferromagnetic layer on one side of the insulating layer In and the wiring W, and then removing the portions other than those that will become the first conductive portion 51 and the second conductive portion 52. The removed portions are filled with, for example, the insulating layer In.

Next, the underlayer 40, the first ferromagnetic layer 10, and the nonmagnetic layer 30 are laminated in this order on the first conductive section 51, the second conductive section 52, and the insulating layer In. Then, a resist is formed on a part of the nonmagnetic layer 30. Next, the underlayer 40, the first ferromagnetic layer 10, and the nonmagnetic layer 30 are processed by performing dry etching from the z direction through the resist. The yz cross-sectional shape of the processed laminate is rectangular or trapezoidal.

Next, an ion beam is irradiated from an oblique direction, targeting the first ferromagnetic layer 10 of the stack. The ion beam irradiation causes the first ferromagnetic layer 10 to recess toward the center of the stack in the y direction. After that, a second ferromagnetic layer 20 is laminated at a position overlapping the first ferromagnetic layer 10.

Finally, the irradiation angle of the ion beam with respect to the xy plane is reduced, and the ion beam is irradiated from the side of the laminate to slim the entire laminate. Slimming reduces the size of the laminate. Finally, the periphery of the laminate is filled with an insulating layer In, to obtain the domain wall motion element 100.

In the domain wall motion element 100 according to the first embodiment, impurities are less likely to re-adhere to the side surface of the nonmagnetic layer 30 during slimming. The reason for this will be explained using FIG. 7. FIG. 7 is a schematic diagram for explaining slimming during the manufacture of the domain wall motion element 100 according to the first embodiment.

As described above, during slimming, the ion beam IB is irradiated from the y direction to the laminate consisting of the underlayer 40, the first ferromagnetic layer 10, the nonmagnetic layer 30, and the second ferromagnetic layer 20. It is difficult to irradiate the ion beam IB parallel to the y direction, so the ion beam IB is irradiated from a direction slightly tilted in the z direction with respect to the xy plane. For example, when the first ferromagnetic layer 10 is irradiated with the ion beam IB, the metal particles contained in the first ferromagnetic layer 10 are scattered as particles pt.

In the domain wall motion element 100 according to the first embodiment, the minimum width L10min in the y direction of the first ferromagnetic layer 10 is shorter than the width L30 in the y direction of the nonmagnetic layer 30, so that the nonmagnetic layer 30 acts as a cover and prevents the particles pt from reattaching to the side walls of the nonmagnetic layer 30.

Furthermore, when the first ferromagnetic layer 10 has a second inclined surface s2, the second inclined surface s2 overhangs the first inclined surface s1, which further prevents the particles pt from reaching the sidewall of the nonmagnetic layer 30. Furthermore, when the position at which the width of the first ferromagnetic layer 10 in the y direction is shortest is closer to the nonmagnetic layer 30 than the center of the first ferromagnetic layer 10 in the z direction, the portion closer to the nonmagnetic layer 30 is recessed inward, which further prevents the particles pt from reaching the sidewall of the nonmagnetic layer 30.

In addition, if the milling rate of the nonmagnetic layer 30 and the underlayer 40 is slower than that of the first ferromagnetic layer 10, the side of the first ferromagnetic layer 10 will move inward relative to the side of the nonmagnetic layer 30 and the underlayer 40 as slimming progresses. Therefore, the nonmagnetic layer 30 acts as a cover, and particles pt are more effectively prevented from reattaching to the sidewall of the nonmagnetic layer 30. In addition, if the milling rate of the underlayer 40 is slower than that of the first conductive portion 51 and the second conductive portion 52, the underlayer 40 acts as a cover, and particles pt scattered from the first conductive portion 51 or the second conductive portion 52 can be more effectively prevented from reaching the sidewall of the nonmagnetic layer 30.

Furthermore, if the first ferromagnetic layer 10 contains elements that make up the underlayer 40, the amount of particles pt scattered from the first ferromagnetic layer 10 can be reduced. Furthermore, by making the abundance ratio of the elements that make up the underlayer 40 in the first region R1 higher than in the second region R2, the generation of particles pt from the first region R1, where a path for the particles pt to reach the nonmagnetic layer 30 is easily secured, can be suppressed.

Impurities formed by the adhesion of particles reduce the MR ratio of the domain wall motion element 100 and, in some cases, may short-circuit the first ferromagnetic layer 10 and the second ferromagnetic layer 20. The domain wall motion element 100 according to the first embodiment is highly reliable because it can reduce the adhesion of impurities to the sidewalls of the nonmagnetic layer 30.

An example of the magnetic recording array 200 and domain wall motion element 100 according to the first embodiment has been described in detail above, but the magnetic recording array 200 and domain wall motion element 100 according to the first embodiment can be modified and changed in various ways within the scope of the gist of the present invention.

(First Modification)
8 is a yz cross-sectional view at the center in the x direction of the domain wall motion element 101 according to the first modified example. The domain wall motion element 101 differs from the domain wall motion element 100 in the shape of the side surface of the first ferromagnetic layer 10. In the domain wall motion element 101, the same components as those in the domain wall motion element 100 are denoted by the same reference numerals and will not be described.

The side surface of the first ferromagnetic layer 10 in the y direction shown in FIG. 8 is an inclined surface s3 that is inclined in the y direction with respect to the z direction. The inclined surface s3 is an inclined surface that is inclined away from the center of the first ferromagnetic layer 10 in the y direction, based on the upper end of the side surface of the first ferromagnetic layer 10 on the nonmagnetic layer 30 side.

The width in the y direction of the first surface 10a shown in FIG. 8 is shorter than the width L30 in the y direction of the nonmagnetic layer 30. The width in the y direction of the first ferromagnetic layer 10 shown in FIG. 8 increases from the first surface 10a toward the second surface 10b. The width in the y direction of the first ferromagnetic layer 10 shown in FIG. 8 is shortest at the first surface 10a and longest at the second surface 10b.

In the domain wall motion element 101 according to the first modified example, a portion of the side surface of the first ferromagnetic layer 10 in the y direction is located inside the nonmagnetic layer 30. Therefore, the nonmagnetic layer 30 acts as a canopy, and particles pt scattered from the first ferromagnetic layer 10 can be prevented from reattaching to the side wall of the nonmagnetic layer 30.

(Second Modification)
9 is a yz cross-sectional view at the center in the x direction of the domain wall motion element 102 according to the second modified example. The domain wall motion element 102 differs from the domain wall motion element 100 in the shape of the side surface of the first ferromagnetic layer 10. In the domain wall motion element 102, the same components as those in the domain wall motion element 100 are denoted by the same reference numerals and will not be described.

The domain wall motion element 102 according to the second modified example is the same as the domain wall motion element 100 in that the width in the y direction of the first ferromagnetic layer 10 is maximum at the second surface 10b, but differs in that the width in the y direction of the second surface 10b is shorter than the width in the y direction L30 of the nonmagnetic layer 30. In the domain wall motion element 102 according to the second modified example, for example, the maximum width in the y direction L10max of the first ferromagnetic layer 10 is shorter than the width in the y direction L30 of the nonmagnetic layer 30.

In the domain wall motion element 102 according to the second modified example, the side surface of the first ferromagnetic layer 10 in the y direction is located inside the nonmagnetic layer 30. Therefore, the nonmagnetic layer 30 acts as a canopy, and particles pt scattered from the first ferromagnetic layer 10 can be prevented from reattaching to the side wall of the nonmagnetic layer 30.

(Third Modification)
10 is a yz cross-sectional view at the center in the x direction of the domain wall motion element 103 according to the third modified example. The domain wall motion element 103 differs from the domain wall motion element 100 in that it has a metal layer 60 on the side surface of the second ferromagnetic layer 20. In the domain wall motion element 103, the same components as those in the domain wall motion element 100 are denoted by the same reference numerals and will not be described.

The metal layer 60 is, for example, on the side of the second ferromagnetic layer 20 in the y direction. The metal layer 60 is, for example, in contact with the side surface of the second ferromagnetic layer 20 in the y direction. There may be another layer between the second ferromagnetic layer 20 and the metal layer 60. The other layer is, for example, an oxide film.

The metal layer 60 is not continuous with the second ferromagnetic layer 20. Not continuous means that the interface can be confirmed by a transmission electron microscope. The metal layer 60 is different from the second ferromagnetic layer 20. Different from the second ferromagnetic layer 20 means that the material or composition is different. The metal layer 60 may be a non-magnetic or magnetic material.

The domain wall motion element 103 according to the third modified example has the same effect as the domain wall motion element 100 according to the first embodiment. In addition, the metal layer 60 protrudes outward from the first ferromagnetic layer 10, thereby improving the heat dissipation of the domain wall motion element 103.

Second Embodiment
Fig. 11 is a cross-sectional view of the domain wall motion element 110 according to the second embodiment cut in an xz plane passing through the center in the y direction of the first ferromagnetic layer 70. Fig. 12 is a cross-sectional view of the domain wall motion element 110 cut in a yz plane passing through the center in the x direction of the domain wall motion element 110. A plan view of the domain wall motion element 110 according to the second embodiment from the z direction is equivalent to Fig. 4.

The domain wall motion element 110 has, for example, a first ferromagnetic layer 70, a second ferromagnetic layer 80, a nonmagnetic layer 30, an underlayer 40, a first conductive portion 51, and a second conductive portion 52. In the domain wall motion element 110, configurations similar to those in the first embodiment are given the same reference numerals. The first ferromagnetic layer 70 is located closer to the substrate Sub than the second ferromagnetic layer 0.

When writing data to the domain wall motion element 110, a write current is passed through the second ferromagnetic layer 80 between the first conductive portion 51 and the second conductive portion 52. When reading data from the domain wall motion element 100, a read current is passed between the first conductive portion 51 or the second conductive portion 52 and the first ferromagnetic layer 70.

The first ferromagnetic layer 70 has a magnetization _M70 oriented in one direction. The first ferromagnetic layer 70 is a magnetization fixed layer and a magnetization reference layer. The first ferromagnetic layer 70 is functionally equivalent to the second ferromagnetic layer 20 according to the first embodiment. The domain wall motion element 110 has a bottom pin structure in which the magnetization fixed layer is on the substrate Sub side. The first ferromagnetic layer 70 can be made of the same material as the second ferromagnetic layer 20. The first ferromagnetic layer 70 may contain an element that constitutes the underlayer 40.

A write current is passed through the second ferromagnetic layer 80. The second ferromagnetic layer 80 is functionally similar to the first ferromagnetic layer 10 according to the first embodiment. The second ferromagnetic layer 80 may be made of the same material as the first ferromagnetic layer 10.

The second ferromagnetic layer 80 is a layer capable of magnetically recording information by changing the internal magnetic state. The second ferromagnetic layer 80 may be called a magnetic recording layer or a domain wall displacement layer. The second ferromagnetic layer 80 has magnetization fixed regions 81 and 82 and a domain wall displacement region 83. The magnetization _M81 of the magnetization fixed region 81 and the magnetization _M82 of the magnetization fixed region 82 are oriented in opposite directions. The domain wall displacement region 83 has a first magnetic domain 83A and a second magnetic domain 83B. The boundary between the first magnetic domain 83A and the second magnetic domain 83B is a domain wall DW. The magnetization _M83A and the magnetization _M84A are oriented in opposite directions across the domain wall DW.

As shown in FIG. 12, the shortest width L70min of the first ferromagnetic layer 70 in the y direction is shorter than the width L30 of the nonmagnetic layer 30 in the y direction. The width of the first ferromagnetic layer 70 in the y direction varies depending on the position in the z direction. For example, the first surface 70a and the second surface 70b of the first ferromagnetic layer 70 have different widths in the y direction. The width of the first ferromagnetic layer 70 in the y direction narrows from the first surface 10a to the second surface 10b, and after reaching the shortest width L70min, it widens. The position of the shortest width L70min is, for example, closer to the nonmagnetic layer 30 than the center of the first ferromagnetic layer 10 in the z direction. The maximum width L70max of the first ferromagnetic layer 70 in the y direction is, for example, longer than the width L30 of the nonmagnetic layer 30 in the y direction.

The y-direction side surface of the first ferromagnetic layer 70 is, for example, inclined in the y-direction with respect to the z-direction. The y-direction side surface of the first ferromagnetic layer 70 can be divided into a first inclined surface s1 and a second inclined surface s2. The y-direction side surface of the first ferromagnetic layer 70 is, for example, recessed with respect to a virtual plane extending downward in the z-direction from the y-direction end of the nonmagnetic layer 30.

The milling rate of the nonmagnetic layer 30 is, for example, slower than the milling rate of the first ferromagnetic layer 70. The milling rate of the underlayer 40 is, for example, slower than the milling rate of the first ferromagnetic layer 70.

In the domain wall motion element 110 according to the second embodiment, the shortest width L70min in the y direction of the first ferromagnetic layer 70 is shorter than the width L30 in the y direction of the nonmagnetic layer 30, so that the nonmagnetic layer 30 acts as a cover and prevents the particles pt from reattaching to the side walls of the nonmagnetic layer 30. The domain wall motion element 110 according to the second embodiment has the same effect as the domain wall motion element 100 according to the first embodiment. In addition, the domain wall motion element 110 according to the second embodiment can be modified in the same manner as the first embodiment.

The above describes the preferred embodiments of the present invention in detail. The characteristic configurations of each embodiment and variant may be combined with each other.

10, 70 First ferromagnetic layer 10a, 70a First surface 10b, 70b Second surface 20, 80 Second ferromagnetic layer 30 Nonmagnetic layer 40 Underlayer 51 First conductive portion 52 Second conductive portion 60 Metal layer 100, 101, 102, 103, 110 Domain wall motion element 200 Magnetic recording array L10max Maximum width L10min Minimum width L30 Width R1 First region R2 Second region s1 First inclined surface s2 Second inclined surface s3 Inclined surface

Claims (12)

A first ferromagnetic layer, a non-magnetic layer, and a second ferromagnetic layer are laminated in this order from the side closest to the substrate,
In a cross section cut along a second direction perpendicular to a first direction in which the first ferromagnetic layer extends as viewed from the stacking direction,
The minimum width of the first ferromagnetic layer in the second direction is shorter than the width of the nonmagnetic layer in the second direction.
Ku,
In a cut surface along the stacking direction and the second direction, a side surface of the first ferromagnetic layer has a first inclined surface and a second inclined surface,
the first inclined surface is inclined from a lower end of the first ferromagnetic layer on a side closer to the substrate toward a center of the first ferromagnetic layer in the second direction,
a second inclined surface inclined from an upper end of the first ferromagnetic layer on a side farther from the substrate toward a center of the first ferromagnetic layer in the second direction . The domain wall motion element according to claim 1, wherein the width in the second direction of the first surface of the first ferromagnetic layer on the nonmagnetic layer side is shorter than the width in the second direction of the nonmagnetic layer. The domain wall motion element according to claim 1 or 2, wherein the position where the width of the first ferromagnetic layer in the second direction is shortest is located on the non-magnetic layer side from the center of the first ferromagnetic layer in the stacking direction. The domain wall motion element according to any one of claims 1 to 3, wherein the maximum width of the first ferromagnetic layer in the second direction is shorter than the width of the nonmagnetic layer in the second direction. The domain wall motion element according to any one of claims 1 to 3, wherein the width in the second direction of the second surface of the first ferromagnetic layer on the side farther from the nonmagnetic layer is longer than the width in the second direction of the nonmagnetic layer. The domain wall motion element according to any one of claims 1 to 5, wherein the thickness of the non-magnetic layer is 30 Å or more. The domain wall motion element according to any one of claims 1 to 6, wherein the milling rate of the nonmagnetic layer is slower than the milling rate of the first ferromagnetic layer. an underlayer is further provided on the opposite side of the first ferromagnetic layer to the nonmagnetic layer;
8. The domain wall motion element according to claim 1, wherein the underlayer has a milling rate slower than that of the first ferromagnetic layer. the first ferromagnetic layer contains an element constituting the underlayer,
9. The domain wall motion element of claim 8, wherein the abundance ratio of the element is higher in a first region located on the underlayer side of a position in the stacking direction where the width of the first ferromagnetic layer in the second direction is shortest than in a second region located on the non-magnetic layer side of a position in the stacking direction where the width of the first ferromagnetic layer in the second direction is shortest. a first conductive portion and a second conductive portion sandwiching the nonmagnetic layer in the first direction and electrically connected to the first ferromagnetic layer via the underlayer;
a width in the second direction of each of the first conductive portion and the second conductive portion is greater than a width in the second direction of the first ferromagnetic layer,
10. The domain wall motion element according to claim 8, wherein a milling rate of the underlayer is slower than a milling rate of the first conductive portion and the second conductive portion. The domain wall motion element according to any one of claims 1 to 10, further comprising a metal layer different from the second ferromagnetic layer on the side of the second ferromagnetic layer in the second direction. A magnetic recording array having a plurality of domain wall motion elements according to any one of claims 1 to 11.

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