Patent Publication Number: US-2022216394-A1

Title: Magnetic domain wall moving element and magnetic array

Description:
BACKGROUND 
     Field 
     The present invention relates to a magnetic domain wall moving element and a magnetic array. 
     Description of Related Art 
     Attention is focused on next-generation non-volatile memories which will replace flash memories and the like in which sizes thereof have reached the limit thereof. For example, magnetoresistive random access memories (MRAMs), resistance random access memories (ReRAMs), phase change random access memories (PCRAM), and the like are known as next-generation non-volatile memories. 
     MRAMs utilize a change in resistance value caused due to a change in direction of magnetization for data recording. Data recording is carried out using each of magnetoresistance change elements constituting MRAMs. For example, Japanese Patent No. 5441005 describes a magnetoresistance change element (a magnetic domain wall moving element) in which multi-valued data can be recorded by moving a domain wall in a magnetic recording layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a constitution diagram of a magnetic array according to a first embodiment. 
         FIG. 2  is a cross-sectional view of a characteristic part of the magnetic array according to the first embodiment. 
         FIG. 3  is a perspective view of a magnetic domain wall moving element according to the first embodiment. 
         FIG. 4  is a cross-sectional view of the magnetic domain wall moving element according to the first embodiment. 
         FIG. 5  is an enlarged cross-sectional view of the vicinity of a ferromagnetic layer of the magnetic domain wall moving element according to the first embodiment. 
         FIG. 6  is an enlarged cross-sectional view of the vicinity of a ferromagnetic layer of another example of the magnetic domain wall moving element according to the first embodiment. 
         FIG. 7  is a cross-sectional view of a magnetic domain wall moving element according to a first modified example. 
         FIG. 8  is a cross-sectional view of a magnetic domain wall moving element according to a second modified example. 
         FIG. 9  is a cross-sectional view of a magnetic domain wall moving element according to a third modified example. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment will be described in detail below with reference to the drawings as appropriate. In the drawings used in the following description, enlarged characteristic parts may be illustrated for the sake of easily understanding the features of the present invention for convenience in some cases and the dimensional ratios of the constituent elements may differ from those of the actual constituent elements in some cases. The materials, the dimensions, and the like exemplified in the following description are examples, the present invention is not limited thereto, and it is possible to carry out modifications as appropriate within a range in which the effects of the present invention are exhibited. 
     A magnetic domain wall moving element according to the embodiment includes a magnetic recording layer, a ferromagnetic layer, and a non-magnetic layer arranged between the magnetic recording layer and the ferromagnetic layer, the ferromagnetic layer contains an additive element dispersed therein, and the additive element is any one or more of H, He, Ne, Ar, Kr, Xe, N, C, Ag, Cu, Hg, Au, Pb, Zn, and Bi. In the magnetic domain wall moving element according to the embodiment, an additive element exhibiting diamagnetism minimizes a leakage magnetic field from the ferromagnetic layer. 
     First, directions are defined. An x direction and a y direction are directions which are substantially parallel to one surface of a substrate Sub (refer to  FIG. 2 ) which will be described later. The x direction is a direction in which a magnetic recording layer  10  which will be described later extends. The y direction is a direction which is orthogonal to the x direction. A z direction is a direction from the substrate Sub which will be described later toward magnetic domain wall moving elements  100 , and for example, is a direction in which the magnetic recording layer  10  is laminated. Hereinafter, a +z direction may be expressed as the term “up or upward” and a −z direction may be expressed as the term “down or downward” in some cases. The terms “up, upward, down, and downward” do not necessarily coincide with a direction in which a gravitational force is applied. Furthermore, in this specification, “extending in the x direction” means that, for example, the dimension in the x direction is larger than the smallest dimension among the dimensions in the x direction, the y direction, and the z direction. The same applies to the case of extending in the other directions. 
     First Embodiment 
       FIG. 1  is a constitution diagram of a magnetic array according to a first embodiment. A magnetic array  200  includes a plurality of magnetic domain wall moving elements  100 , a plurality of write lines WL, a plurality of common lines CL, a plurality of read lines RL, a plurality of first switching elements Sw 1 , a plurality of second switching elements Sw 2 , and a plurality of third switching elements Sw 3 . The magnetic array  200  can be used, for example, in a magnetic memory, a product-sum calculator, and a neuromorphic device. 
     Each of the write lines WL electrically connects a power supply to one or more of the magnetic domain wall moving elements  100 . The power supply is connected to the magnetic array  200  at the time of use. The power supply is connected to one end of each of the write lines WL. 
     The common lines CL are lines which can be used both when data is written and when data is read. Each of the common lines CL electrically connects a reference potential to one or more of the magnetic domain wall moving elements  100 . The reference potential is, for example, a ground. Each of the common lines CL may be provided in each of the plurality of magnetic domain wall moving elements  100  or may be provided over the plurality of magnetic domain wall moving elements  100 . 
     Each of the read lines RL electrically connects the power supply to one or more of the magnetic domain wall moving elements  100 . The power supply is connected to the magnetic array  200  at the time of use. The power supply is connected to one end of each of the write lines WL. 
     Each of the first switching elements Sw 1 , each of the second switching elements Sw 2 , and each of the third switching elements Sw 3  illustrated in  FIG. 1  are connected to one of the plurality of magnetic domain wall moving elements  100 . The first switching element Sw 1  is connected between each of the magnetic domain wall moving elements  100  and the write line WL. The second switching element Sw 2  is connected between each of the magnetic domain wall moving elements  100  and the common line CL. The third switching element Sw 3  is connected between each of the magnetic domain wall moving elements  100  and the read line RL. 
     If the first switching element Sw 1  and the second switching element Sw 2  are turned on, a write current flows between a prescribed write line WL and common line CL connected to the magnetic domain wall moving element  100 . If the second switching element Sw 2  and the third switching element Sw 3  are turned on, a read current flows between a prescribed common line CL and read line RL connected to the magnetic domain wall moving elements  100 . 
     The first switching elements Sw 1 , the second switching elements Sw 2 , and the third switching elements Sw 3  are elements configured to control a flow of an electric current. The first switching elements Sw 1 , the second switching elements Sw 2 , and the third switching elements Sw 3  may be, for example, transistors, elements in which a phase change of a crystal layer is utilized such as ovonic threshold switches (OTSs), elements in which a change in band structure is utilized such as metal-insulator transition (MIT) switches, elements in which a breakdown voltage is utilized such as Zener diodes and avalanche diodes, and elements whose conductivity changes along with a change in atomic position. 
     Any one of the first switching elements Sw 1 , the second switching elements Sw 2 , and the third switching elements Sw 3  may be shared by the magnetic domain wall moving elements  100  connected to the same line. For example, when each of the first switching elements Sw 1  is shared, one of the first switching elements Sw 1  is provided upstream of each of the write lines WL. For example, when each of the second switching elements Sw 2  is shared, one of the second switching elements Sw 2  is provided upstream of each of the common lines CL. For example, when each of the third switching elements Sw 3  is shared, one of the third switching elements Sw 3  is provided upstream of each of the read lines RL. 
       FIG. 2  is a cross-sectional view of a characteristic part of the magnetic array  200  according to the first embodiment.  FIG. 2  is a cross section of one of the magnetic domain wall moving elements  100  in  FIG. 1  taken along an xz plane passing through a center of a width of the magnetic recording layer  10  in the y direction. 
     The first switching elements Sw 1  and the second switching elements Sw 2  illustrated in  FIG. 2  are transistors Tr. Each of the transistors Tr includes a gate electrode G, a gate insulating film GI, and a source region S and a drain region D formed on the substrate Sub. The substrate Sub is, for example, a semiconductor substrate. Each of the third switching elements Sw 3  is electrically connected to an electrode E and is located, for example, at a different position in the y direction. 
     Each of the transistors Tr and each of the magnetic domain wall moving elements  100  are electrically connected to each other via a via line V. The via line V contains a material with conductivity. For example, the via line V extends in the z direction. For example, the via line V is formed, for example, in an opening portion of an insulating layer In. 
     The magnetic domain wall moving elements  100  are electrically isolated from the transistors Tr using the insulating layer In except for the via line V. The insulating layer In is an insulating layer configured to insulate between lines of a multilayer line and between elements. Examples of the insulating layer In include silicon oxides (SiO x ), silicon nitrides (SiN x ), silicon carbide (SiC), chromium nitride, silicon carbonitride (SiCN), silicon oxynitride (SiON), aluminum oxide (Al 2 O 3 ), zirconium oxides (ZrO x ), and the like. 
       FIG. 3  is a perspective view of the magnetic domain wall moving element  100 .  FIG. 4  is a cross-sectional view of the magnetic domain wall moving element  100  taken along the xz plane passing through the center of the magnetic recording layer  10  in the y direction. 
     The magnetic domain wall moving element  100  includes, for example, the magnetic recording layer  10 , a non-magnetic layer  20 , a ferromagnetic layer  30 , a first conductive layer  41 , and a second conductive layer  42 . The periphery of the magnetic domain wall moving element  100  is covered with an insulating layer  51  and an insulating layer  52 . When data is written to the magnetic domain wall moving element  100 , a write current flows through the magnetic recording layer  10  between the first conductive layer  41  and the second conductive layer  42 . When data is read from the magnetic domain wall moving element  100 , a read current flows between the first conductive layer  41  or the second conductive layer  42  and the ferromagnetic layer  30 . 
     The magnetic recording layer  10  is a part which extends in the x direction and to which a write current is to be applied. The magnetic recording layer  10  has, for example, a rectangular shape in which the x direction is a long axis and the y direction is a short axis when viewed in a plan view from the z direction. The magnetic recording layer  10  is connected to the first conductive layer  41  and the second conductive layer  42 . A write current flows along the magnetic recording layer  10  from the first conductive layer  41  toward the second conductive layer  42  or from the second conductive layer  42  toward the first conductive layer  41 . 
     The magnetic recording layer  10  is a layer in which information can be magnetically recorded using a change in internal magnetic state. The magnetic recording layer  10  may be referred to as a “ferromagnetic layer or a domain wall moving layer” in some cases. 
     The magnetic recording layer  10  includes, for example, magnetization fixing regions  11  and  12  and a domain wall moving region  13 . The domain wall moving region  13  is arranged between two regions which are the magnetization fixing regions  11  and  12 . 
     The magnetization fixing region  11  is a region of the magnetic recording layer  10  that overlaps the first conductive layer  41  when viewed from the z direction. The magnetization fixing region  12  is a region of the magnetic recording layer  10  that overlaps the second conductive layer  42  when viewed from the z direction. Magnetizations M 11  and M 12  of the magnetization fixing regions  11  and  12  are not easily reversed as compared with magnetizations M 13A  and M 13B  of the domain wall moving region  13  and magnetization reversal is not performed even if an external force of a threshold value in which the magnetizations M 13A  and M 13B  of the domain wall moving region  13  are reversed is applied. For this reason, it can be said that the magnetizations M 11  and M 12  of the magnetization fixing regions  11  and  12  are fixed to the magnetizations M 13A  and M 13B  of the domain wall moving region  13 . That is to say, in this specification, the expression “magnetization is fixed” means that a magnetization is not reversed even if a write current of a reverse current density in which the magnetization of the domain wall moving region  13  is reversed is applied. 
     The magnetization M 11  of the magnetization fixing region  11  and the magnetization M 12  of the magnetization fixing region  12  are oriented in different directions. The magnetization M 11  of the magnetization fixing region  11  and the magnetization M 12  of the magnetization fixing region  12  are oriented, for example, in opposite directions. The magnetization M 11  of the magnetization fixing region  11  is oriented, for example, in the +z direction and the magnetization M 12  of the magnetization fixing region  12  is oriented, for example, in the −z direction. 
     The domain wall moving region  13  has a first magnetic domain  13 A and a second magnetic domain  13 B. The first magnetic domain  13 A is adjacent to the magnetization fixing region  11 . A magnetization M 13A  of the first magnetic domain  13 A has an influence on the magnetization M 11  of the magnetization fixing region  11  and is oriented, for example, in the same direction as the magnetization M 11  of the magnetization fixing region  11 . The second magnetic domain  13 B is adjacent to the magnetization fixing region  12 . A magnetization M 13B  of the second magnetic domain  13 B has an influence on the magnetization M 12  of the magnetization fixing region  12  and is oriented, for example, in the same direction as the magnetization M 12  of the magnetization fixing region  12 . For this reason, the magnetization M 13A  of the first magnetic domain  13 A and the magnetization M 13B  of the second magnetic domain  13 B are oriented in different directions. The magnetization M 13A  of the first magnetic domain  13 A and the magnetization M 13B  of the second magnetic domain  13 B are oriented, for example, in opposite directions. 
     A boundary between the first magnetic domain  13 A and the second magnetic domain  13 B is a domain wall DW. The domain wall DW moves in the domain wall moving region  13 . In principle, the domain wall DW does not enter the magnetization fixing regions  11  and  12  except when an external force equal to or more than expected is applied. 
     If a ratio between the first magnetic domain  13 A and the second magnetic domain  13 B in the domain wall moving region  13  changes, the domain wall DW moves. The domain wall DW moves by causing a write current to flow in the x direction of the domain wall moving region  13 . For example, if a write current (for example, a current pulse) in a write current in the +x direction (for example, a current pulse) is applied to the domain wall moving region  13 , electrons flow in the −x direction opposite to the current. Thus, the domain wall DW moves in the −x direction. When an electric current flows from the first magnetic domain  13 A toward the second magnetic domain  13 B, spin-polarized electrons in the second magnetic domain  13 B reverse the magnetization M 13A  of the first magnetic domain  13 A. When the magnetization M 13A  of the first magnetic domain  13 A is reversed, the domain wall DW moves in the −x direction. 
     The magnetic recording layer  10  is mainly composed of a magnetic material. The magnetic recording layer  10  preferably has at least one element selected from the group consisting of Fe, Co, Ni, Pt, Pd, Gd, Tb, Mn, Ge, and Ga and preferably contains at least one of Fe, Co, and Ni. 
     Examples of the material used for the magnetic recording layer  10  include laminated films of CoFe and Pt, laminated films of CoFe and Pd, laminated films of Co and Ni, laminated films of Co and Pt, laminated films of Co and Pd, MnGa-based materials, GdCo-based materials, and TbCo-based materials. Ferrimagnetic materials such as MnGa-based materials, GdCo-based materials, and TbCo-based materials have a small saturation magnetization and a small threshold current required for moving the domain wall DW. Furthermore, the laminated films of CoFe and Pt, the laminated films of CoFe and Pd, the laminated films of Co and Ni, the laminated films of Co and Pt, and the laminated films of Co and Pd have a large coercive force and a moving speed of the domain wall DW is reduced. In addition, the material used for the magnetic recording layer  10  may be CoFeB, FeB, CoB, or the like. If such materials are used for the magnetic recording layer  10 , a ratio between changes in magnetic resistance (an MR ratio) of the magnetic domain wall moving elements  100  increases. 
     The ferromagnetic layer  30  is located, for example, on the non-magnetic layer  20 . The ferromagnetic layer  30  has a magnetization M 30  oriented in one direction. The magnetization M 30  of the ferromagnetic layer  30  is less like to be reversed as compared with the magnetizations M 13A  and M 13B  of the domain wall moving region  13  when a prescribed external force is applied to the ferromagnetic layer  30 . The prescribed external force is, for example, an external force applied to the magnetization due to an external magnetic field or an external force applied to the magnetization due to a spin polarization current. The ferromagnetic layer  30  may be referred to as a “magnetization fixed layer” or a “magnetization reference layer” in some cases. 
     A resistance value of the magnetic domain wall moving elements  100  in a direction in which the magnetic domain wall moving elements  100  are laminated changes in accordance with a difference between relative angles of the magnetization M 30  of the ferromagnetic layer  30  and the magnetizations M 13A  and M 13B  of the domain wall moving region  13 . The magnetization M 13A  of the first magnetic domain  13 A is oriented, for example, to the same direction as (to be parallel to) the magnetization M 30  of the ferromagnetic layer  30  and the magnetization M 13B  of the second magnetic domain  13 B is oriented, for example, to an opposite direction (to be antiparallel) to the magnetization M 30  of the ferromagnetic layer  30 . If an area of the first magnetic domain  13 A in a portion in which the first magnetic domain  13 A and the ferromagnetic layer  30  overlap when viewed in a plan view from the z direction increases, a resistance value of the magnetic domain wall moving elements  100  decreases. On the other hand, if an area of the second magnetic domain  13 B in a portion in which the second magnetic domain  13 B and the ferromagnetic layer  30  overlap when viewed in a plan view from the z direction increases, a resistance value of the magnetic domain wall moving elements  100  increases. 
     The ferromagnetic layer  30  contains a ferromagnetic material. The ferromagnetic layer  30 , for example, contains a metal selected from the group consisting of Cr, Mn, Co, Fe, and Ni, an alloy containing at least one of these metals, an alloy containing these metals and at least one or more elements of B, C, and N, and the like. The ferromagnetic layer  30  contains, for example, any element of Co, Fe, and Ni. The ferromagnetic layer  30 , for example, contains Co—Fe, Co—Fe—B, or Ni—Fe. 
     The ferromagnetic layer  30  may be, for example, a Heusler alloy. A Heusler alloy is a half metal and has a high spin polarization. A Heusler alloy contains an intermetallic compound having a chemical composition of XYZ or X 2 YZ, where X represents a Co-, Fe-, or Ni-, Cu-group transition metal element or noble metal element in the periodic table, Y represents a Mn-, V-, Cr-, or Ti-group transition metal or an element of the type X in the periodic table, and Z represents a typical element from Group III to Group V. Examples of the Heusler alloy 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 , Co 2 FeGe 1-c Ga c , and the like. 
     The ferromagnetic layer  30  contains an additive element. The additive element is any one or more of H, He, Ne, Ar, Kr, Xe, N, C, Ag, Cu, Hg, Au, Pb, Zn, and Bi. These additive elements have a negative magnetic susceptibility and exhibit diamagnetism. Diamagnetism is a phenomenon in which, when a magnetic field is applied, magnetization in an opposite direction to that of the magnetic field occurs. The additive element does not have spontaneous magnetization and exhibits diamagnetic properties only when a magnetic field is applied. 
     These additive elements do not easily combine with magnetic elements and readily exhibit diamagnetic performance as a single element. Furthermore, among these addive elements, He, Ne, Ar, Kr, and Xe do not have unpaired electrons and readily exhibit diamagnetism even with the element alone. If a substance has unpaired electrons, the unpaired electrons may develop paramagnetism and the effect of diamagnetism may not be easily obtained in some cases. 
     Also, among these additive elements, C, Ag, Hg, Au, Pb, Zn, and Bi have a large absolute value of diamagnetic susceptibility in the state of closed shell ions and exhibit strong diamagnetism. Furthermore, among these additive elements, Ag, Cu, Au, Zn, Bi, and C are known to exhibit strong diamagnetism even at room temperature. 
     Also, among these additive elements, H, N, and C have a small atomic radius, enter a crystal lattice of the ferromagnetic layer  30 , and form an intrusive solid solution. H, N, and C enter in the state of closed shell ions and easily develop diamagnetism. 
     Furthermore, among these additive elements, He, Ne, Ar, Kr, and Xe are rare gases and the outermost shell electrons have a closed shell structure and thus easily exhibit diamagnetism. In addition, rare gases are inert and substantially do not allow chemical reactions. Therefore, He, Ne, Ar, Kr, and Xe enter the ferromagnetic layer  30  in a stable state. 
     Also, among these additive elements, Bi, Cu, Pb, Hg, Ag, Au, and Zn and a ferromagnetic material of the ferromagnetic layer  30  are converted into alloys, exist in the state of closed shell ions, and easily exhibit diamagnetism. 
     The additive elements are dispersed in the ferromagnetic layer  30 . The additive elements are dispersed, for example, over the entire in-plane direction of the ferromagnetic layer  30 . The additive elements are also confirmed, for example, in a region 20% or more inside a width of the ferromagnetic layer  30  from an outer surface of the ferromagnetic layer  30 . The details of the additive elements dispersed in the ferromagnetic layer  30  can be confirmed using energy dispersive X-ray analysis (EDS). 
     Content concentrations of the additive elements in the ferromagnetic layer  30  are, for example, preferably 0.14 atm % or more, and more preferably 0.35 atm % or more. Furthermore, the content concentrations of the additive elements in the ferromagnetic layer  30  are, for example, preferably 20 atm % or less, and more preferably 15 atm % or less. Each of the content concentrations of the additive elements are an average content concentration in the ferromagnetic layer  30 . The average content concentration is an average value of the concentrations of the additive element at  10  different points of the ferromagnetic layer  30  measured using an EDS. When a sufficient amount of additive elements is contained, the diamagnetism produced by the additive elements can sufficiently minimize a leakage magnetic field occurring from the ferromagnetic layer  30 . Furthermore, when the additive element is a prescribed value or less, it is possible to prevent a decrease in ferromagnetic characteristics inherent in the ferromagnetic layer  30 . 
       FIG. 5  is an enlarged cross-sectional view of the vicinity of the ferromagnetic layer  30  of the magnetic domain wall moving element  100  according to the first embodiment. As illustrated in  FIG. 5 , the ferromagnetic layer  30  may have a first region  31  and a second region  32  therein. The first region  31  and the second region  32  are regions which extend in the in-plane direction and regions obtained by dividing the ferromagnetic layer  30  in the z direction. The second region  32  is located farther from the non-magnetic layer  20  than the first region  31 . The content concentrations of the additive elements in the first region  31  and the second region  32  differ. 
     The first region  31  has higher content concentrations of the additive elements than that of the second region  32 . The content concentrations of the additive elements of the first region  31  and the second region  32  are measured through the following procedure. First, the content concentrations of the additive elements at two points at different positions in the z direction are measured at each of five different locations in the x direction. Hereinafter, of the two points at different positions in the z directions, a point near the non-magnetic layer  20  is referred to as a “first point” and a point located farther from the non-magnetic layer  20  than the first point is referred to as a “second point”. Furthermore, when the content concentrations of the additive elements measured at the first point are higher than the content concentrations of the additive elements measured at the second point in each of the five locations, it is assumed that the content concentrations of the additive elements of the first region  31  are higher than the content concentrations of the additive elements of the second region  32 . 
     The content concentrations of the additive elements in the first region  31  are, for example, preferably 1.1 times or more, and more preferably 1.4 times or more the content concentrations of the additive elements in the second region  32 . 
     A leakage magnetic field from the ferromagnetic layer  30  occurs from a first surface  30 A on the non-magnetic layer  20  side. If the content concentrations of the additive elements exhibiting diamagnetism are high near the first surface  30 A, it is possible to more efficiently minimize the leakage magnetic field from the ferromagnetic layer  30 . 
     On the other hand, the first region  31  may have, for example, lower content concentrations of the additive elements than those of the second region  32 . When the content concentrations of the additive elements measured at the first point are lower than the content concentrations of the additive elements measured at the second point in each of the five different locations in the x direction, it is assumed that the content concentrations of the additive elements of the first region  31  are lower than the content concentrations of the additive elements of the second region  32 . 
     The content concentrations of the additive elements in the second region  32  are, for example, preferably 1.1 times or more, and more preferably 1.4 times or more the content concentrations of the additive elements in the first region  31 . 
     A change in magnetic resistance (an MR ratio) of the magnetic domain wall moving element  100  changes in accordance with a relative angle between magnetizations of two ferromagnetic materials having the non-magnetic layer  20  arranged therebetween. For this reason, a state of magnetization in the vicinity of the first surface  30 A has an influence of the MR ratio of the magnetic domain wall moving element  100 . Each of the additive elements is one of the causes of disturbing the orientation of the magnetization. In addition, when the content concentrations of the additive elements in the vicinity of the first surface  30 A are low, it is possible to minimize a decrease in the MR ratio of the magnetic domain wall moving element  100 . 
     Also,  FIG. 6  is an enlarged cross-sectional view of the vicinity of the ferromagnetic layer  30  of another example of the magnetic domain wall moving element  100  according to the first embodiment. As illustrated in  FIG. 6 , the ferromagnetic layer  30  may have a central region  33  and an outer circumferential region  34  therein. The central region  33  is a region near a center of the ferromagnetic layer  30  in the xy plane. The outer circumferential region  34  is located on an outer side of the central region  33 . If the central region  33  and the outer circumferential region  34  are at the same height position, the central region  33  and the outer circumferential region  34  do not need to exist over the entire z direction. 
     The outer circumferential region  34  has, for example, higher the content concentrations of the additive elements than those of the central region  33 . The content concentrations of the additive elements between the outer circumferential region  34  and the central region  33  are compared at the same height position in the z direction. When five different points in the x direction are measured and the content concentrations of the additive elements measured at measurement points on the outer side of the ferromagnetic layer  30  are higher than the content concentrations of the additive elements measured at measurement points on the inner side thereof, it is assumed that the content concentrations of the additive elements of the outer circumferential region  34  are higher than the content concentrations of the additive elements of the central region  33 . 
     The content concentrations of the additive elements in the outer circumferential region  34  are, for example, preferably 1.1 times or more, and more preferably 1.4 times or more the content concentrations of the additive elements in the central region  33 . 
     The leakage magnetic field from the ferromagnetic layer  30  strongly occurs in the vicinity of an outer circumference of the ferromagnetic layer  30 . If the content concentrations of the additive elements in the outer circumferential region  34  having a large amount of leakage magnetic field to occur increase, it is possible to more efficiently minimize the leakage magnetic field from the ferromagnetic layer  30 . 
     Also, the ferromagnetic layer  30  may share the first region  31  and the second region  32  with the central region  33  and the outer circumferential region  34 . For example, the leakage magnetic field from the ferromagnetic layer  30  particularly occurs in the vicinity of an outer circumference of the first surface  30 A of the ferromagnetic layer  30 . For this reason, the content concentrations of the additive elements in the vicinity of the outer circumference of the first surface  30 A may be higher than the content concentrations of the additive elements in the other parts. 
     A film thickness of the ferromagnetic layer  30  is preferably 1.5 nm or less, and more preferably 1.0 nm or less when an easy axis of magnetization of the ferromagnetic layer  30  is assumed to be directed in the z direction (the ferromagnetic layer is formed as a perpendicular magnetization film). If a thin film thickness of the ferromagnetic layer  30  is provided, at an interface between the ferromagnetic layer  30  and another layer (the non-magnetic layer  20 ), perpendicular magnetic anisotropy (interfacial perpendicular magnetic anisotropy) is added to the ferromagnetic layer  30  and the magnetization of the ferromagnetic layer  30  is easily oriented in the z direction. 
     When the easy axis of magnetization of the ferromagnetic layer  30  is assumed to be directed in the z direction (the ferromagnetic layer  30  is formed as a perpendicular magnetization film), it is desirable that the ferromagnetic layer  30  be 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 an intermediate layer made of a material selected from the group consisting of W, Mo, Ta, Ru, Ti, Cr, MgO, MgAlO, AlO, Mg, and Ir may be provided at any position on the laminate. If the intermediate layer is provided in the ferromagnetic material, it is possible to add interfacial perpendicular magnetic anisotropy and the magnetization of the ferromagnetic layer  30  is easily oriented in the z direction. 
     “Non-Magnetic Layer” 
     The non-magnetic layer  20  is arranged between the magnetic recording layer  10  and the ferromagnetic layer  30 . The non-magnetic layer  20  is laminated, for example, on one surface of the magnetic recording layer  10 . 
     The non-magnetic layer  20  is made of, for example, a non-magnetic insulator, a semiconductor, or a metal. Examples of the non-magnetic 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 of these are replaced with Zn, Be, and the like. These materials have a large bandgap and excellent insulation. When the non-magnetic layer  20  is made of a non-magnetic insulator, the non-magnetic layer  20  is a tunnel barrier layer. Examples of the non-magnetic metal include Cu, Au, Ag, and the like. Examples of the non-magnetic semiconductor include Si, Ge, CuInSe 2 , CuGaSe 2 , Cu(In, Ga)Se 2 , and the like. 
     The non-magnetic layer  20  may contain the above-described additive elements. If the non-magnetic layer  20  contains additive elements, it is possible to minimize the leakage magnetic field from the ferromagnetic layer  30 . If the additive elements contained in the non-magnetic layer  20  exhibit diamagnetism, a small intensity of the leakage magnetic field reaching the magnetic recording layer  10  is provided. 
     A thickness of the non-magnetic layer  20  is preferably 20 Å or more, and more preferably 25 Å. If a large thickness of the non-magnetic layer  20  is provided, a resistance area product (RA) of the magnetic domain wall moving element  100  increases. The resistance area product (RA) of the magnetic domain wall moving element  100  is preferably 1×10 4  Ωμm 2  or more, and more preferably 5×10 4  Ωμm 2  or more. The resistance area product (RA) of the magnetic domain wall moving element  100  is represented by a product of an element resistance of one of the magnetic domain wall moving elements  100  and an element cross-sectional area of the magnetic domain wall moving element  100  (an area of a cut surface obtained by cutting the non-magnetic layer  20  in the xy plane). 
     The magnetic domain wall moving element  100  may have a layer other than the magnetic recording layer  10 , the non-magnetic layer  20 , and the ferromagnetic layer  30 . For example, the layer may be provided on a surface of the ferromagnetic layer  30  opposite to the non-magnetic layer  20  to have a spacer layer arranged between the layer and the ferromagnetic layer  30 . When the ferromagnetic layer  30 , the spacer layer, and an antiferromagnetic layer are provided to have a synthetic antiferromagnetic structure (an SAF structure), the coercive force of the ferromagnetic layer  30  increases. Furthermore, an underlayer may be provided on a lower surface of the magnetic recording layer  10  and a cap layer may be provided on an upper surface of the ferromagnetic layer  30 . 
     The first conductive layer  41  and the second conductive layer  42  are connected to the magnetic recording layer  10 . The first conductive layer  41  and the second conductive layer  42  may be connected to the same surface of the magnetic recording layer  10  or may be connected to different surfaces. The second conductive layer  42  is located apart from the first conductive layer  41  and connected to the magnetic recording layer  10 . The first conductive layer  41  is connected to, for example, a first end part of the magnetic recording layer  10  and the second conductive layer  42  is connected to, for example, a second end part of the magnetic recording layer  10 . The first conductive layer  41  and the second conductive layer  42  are, for example, connecting parts between the via line V and the magnetic recording layer  10 . 
     The first conductive layer  41  and the second conductive layer  42  contains, for example, magnetic materials. A magnetization M 41  of the first conductive layer  41  and a magnetization M 42  of the second conductive layer  42  are oriented in one direction. The magnetization M 41  is oriented, for example, in the +z direction. The magnetization M 42  is oriented, for example, in the −z direction. The magnetization M 41  of the first conductive layer  41  and the magnetization M 11  of the magnetization fixing region  11  are oriented, for example, in the same direction. The magnetization M 42  of the second conductive layer  42  and the magnetization M 12  of the magnetization fixing region  12  are oriented, for example, in the same direction. The first conductive layer  41  is fixed to the magnetization M 11  of the magnetization fixing region  11 . The second conductive layer  42  is fixed to the magnetization M 12  of the magnetization fixing region  12 .\ 
     Examples of the first conductive layer  41  and the second conductive layer  42  include a metal selected from the group consisting of Cr, Mn, Co, Fe, and Ni, an alloy containing one or more of these metals, and an alloy containing these metals and at least one or more elements of B, C, and N. Examples of the first conductive layer  41  and the second conductive layer  42  include Co—Fe, Co—Fe—B, Ni—Fe, and the like. Furthermore, the first conductive layer  41  and the second conductive layer  42  may have a synthetic antiferromagnetic structure (an SAF structure). 
     The first conductive layer  41  and the second conductive layer  42  may be conductive and may not be made of a magnetic material. A current density of a write current flowing through the magnetic recording layer  10  sharply decreases at a position in which the magnetic recording layer  10 , the first conductive layer  41 , and the second conductive layer  42  overlap. For this reason, even when the first conductive layer  41  and the second conductive layer  42  are not made of a ferromagnetic material, it is possible to prevent the domain wall DW from entering the magnetization fixing regions  11  and  12 . 
     The insulating layers  51  and  52  are a part of the insulating layer In. The insulating layer  51  is located below the magnetic recording layer  10 . Apart of the insulating layer  51  is located between the first conductive layer  41  and the second conductive layer  42 . The insulating layer  52  surrounds lateral sides of the non-magnetic layer  20  and the ferromagnetic layer  30 . The insulating layer  52  is located above the magnetic recording layer  10 . 
     The insulating layers  51  and  52  are a part of the insulating layer In and are made of the same material as the insulating layer In. The insulating layer  52  may have additive elements. The leakage magnetic field from the ferromagnetic layer  30  occurs from, for example, the first surface  30 A of the ferromagnetic layer  30 , goes around a lateral side of the ferromagnetic layer  30 , and recirculates to a second surface  30 B of the ferromagnetic layer  30 . If the insulating layer  52  has the additive elements, it is possible to inhibit the recirculating magnetic field and minimize the leakage magnetic field from the ferromagnetic layer  30 . 
     The direction of magnetization of each layer of the magnetic domain wall moving element  100  can be confirmed, for example, by measuring a magnetization curve. The magnetization curve can be measured using, for example, a magneto optical Kerr effect (MOKE). The measurement using the MOKE is a measurement method in which linearly polarized light is caused to be incident on an object to be measured and which is performed using a magneto-optical effect (a magnetic Kerr effect) in which rotation or the like in a polarization direction thereof occurs. 
     A method for manufacturing the magnetic array  200  will be described below. The magnetic array  200  is formed using a laminating step of each layer and a processing step of processing a part of each layer to have a prescribed shape. For the lamination of each layer, a sputtering method, a chemical vapor deposition (CVD) method, an electron beam vapor deposition method (EB vapor deposition method), an atomic laser deposit method, or the like can be utilized. The processing of each layer can be performed using photolithography or the like. 
     First, the source region S and the drain region D are formed by doping a prescribed position of the substrate Sub with impurities. Subsequently, the gate insulating film GI and the 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 serve as the transistor Tr. 
     Subsequently, the insulating layer In is formed to cover the transistor Tr. Furthermore, the via line V is formed by forming an opening portion in the insulating layer In and filling the opening portion with a conductor. The write lines WL, the common lines CL, and the read lines RL are formed by laminating the insulating layer In to have a prescribed thickness, forming a groove in the insulating layer In, and then filling the groove with a conductor. 
     For example, the first conductive layer  41  and the second conductive layer  42  can be formed by laminating the ferromagnetic layer on the insulating layer In and one surface of the via line V and removing parts other than the parts which are the first conductive layer  41  and the second conductive layer  42 . The removed parts are embedded, for example, with the insulating layer In (the insulating layer  51 ). 
     Subsequently, the magnetic recording layer  10 , the non-magnetic layer  20 , and the ferromagnetic layer  30  are laminated in this order above the first conductive layer  41 , the second conductive layer  42 , and the insulating layer  51 . After that, the magnetic domain wall moving element  100  is obtained by processing the non-magnetic layer  20  and the ferromagnetic layer  30  to have a prescribed shape. 
     The additive elements are added, for example, when a film of the ferromagnetic layer  30  is formed. Since sufficient additive elements are not contained in an alloy only by forming a film in an atmosphere containing the additive elements, an addition treatment is performed. 
     As the addition treatment, for example, a film of the ferromagnetic layer  30  is formed by repeated performing the formation and etching of the magnetic film. The magnetic film is formed in units of several A in an atmosphere in which additive elements are contained. The magnetic film is etched using reverse sputtering in an atmosphere in which additive elements are contained. More additive elements are incorporated into the ferromagnetic layer  30  by repeatedly performing the film formation and etching the magnetic film. Furthermore, the contents of the additive elements contained in the ferromagnetic layer  30  can be adjusted by adjusting the balance between a film thickness to be etched and a film thickness. 
     Also, it is desirable that a gas pressure of a gas containing an additive element when a film of the ferromagnetic layer  30  is formed be higher than a gas pressure when the magnetic recording layer  10  is laminated. Furthermore, it is desirable that an application voltage applied to a sputtering target when a film of the ferromagnetic layer  30  is formed be also higher than that when the magnetic recording layer  10  is laminated. Furthermore, when a gas containing one or more of a H element, a N element, and a C element is mixed in a gas atmosphere at the time of film formation or etching, a diamagnetic material is more easily incorporated into the ferromagnetic layer  30 . 
     Furthermore, when the additive elements are C, Ag, Cu, Hg, Au, Pb, Zn, and Bi, as the addition treatment, for example, a film formation of a magnetic film and a film formation of at least one or more materials of C, Ag, Cu, Hg, Au, Pb, Zn, and Bi are repeatedly performed. The formed film is formed in units of several A. The contents of the additive elements in the ferromagnetic layer  30  can be adjusted by adjusting the balance of each film thickness. When the non-magnetic layer  20  and the insulating layer  52  contain additive elements, the same treatment is performed on these layers at the time of film formation. 
     According to the magnetic domain wall moving element  100  associated with the first embodiment, it is possible to minimize the leakage magnetic field from the ferromagnetic layer  30  reaching the magnetic recording layer  10 . The leakage magnetic field from the ferromagnetic layer  30  is an external magnetic field with respect to the magnetic recording layer  10 . If an external magnetic field is applied to the magnetic recording layer  10 , the domain wall DW may disappear unexpectedly or the domain wall DW may be generated in an unexpected place in some cases. The magnetic domain wall moving element  100  records data using a change in resistance value of the magnetic domain wall moving element  100  accompanied by a change in position of the domain wall DW. A decrease in stability of a position of the domain wall DW is one of the factors for a decrease in reliability of the magnetic domain wall moving element  100 . 
     The additive elements contained in the ferromagnetic layer  30  exhibits diamagnetism. The diamagnetism is a phenomenon in which magnetization occurs in a direction opposite to a direction in which a magnetic field occurs and the additive elements exhibiting diamagnetism creates magnetization in a direction in which a leakage magnetic field is canceled. As a result, it is possible to reduce the leakage magnetic field reaching the magnetic recording layer  10  by canceling a part of the leakage magnetic field using the additive elements exhibiting diamagnetism. 
     Although an example of the magnetic array  200  and the magnetic domain wall moving element  100  according to the first embodiment has been described in detail, the magnetic array  200  and the magnetic domain wall moving element  100  according to the first embodiment can be variously modified and changed within the scope of the gist of the present invention. 
       FIG. 7  is a cross-sectional view of a magnetic domain wall moving element  101  according to a first modified example. In the magnetic domain wall moving element  101  illustrated in  FIG. 7 , a ferromagnetic layer  30  is located closer to a substrate Sub than a magnetic recording layer  10 . Such a magnetic domain wall moving element  101  is referred to as a “bottom pin structure”. When the magnetic domain wall moving element  101  has the bottom pin structure, the same effect as the magnetic domain wall moving element  100  according to the first embodiment can be obtained. 
       FIG. 8  is a cross-sectional view of a magnetic domain wall moving element  102  according to a second modified example. The magnetic domain wall moving element  102  illustrated in  FIG. 8  extends to a position in which a ferromagnetic layer  30 , a first conductive layer  41 , and a second conductive layer  42  overlap in the z direction. The movement of a domain wall DW in the entire region of a domain wall moving region  13  affects a change in resistance of the magnetic domain wall moving element  102  in the z direction and can increase a change width in resistance of the magnetic domain wall moving element  102 . Furthermore, the magnetic domain wall moving element  102  according to the second modified example has the same effect as the magnetic domain wall moving element  100  according to the first embodiment. 
       FIG. 9  is a cross-sectional view of a magnetic domain wall moving element  103  according to a third modified example. The magnetic domain wall moving element  103  illustrated in  FIG. 9  is different from that of  FIG. 4  in that upper surfaces of magnetization fixing regions  11  and  12  are etched. When the processes of a magnetic recording layer  10 , a non-magnetic layer  20 , and a ferromagnetic layer  30  are performed at the same time, a manufacturing process is simplified. The magnetic domain wall moving element  103  can have the same effect as the magnetic domain wall moving element  100  according to the first embodiment. 
     The preferred embodiments of the present invention have been described in detail above. The characteristic constitution in the embodiments and modifications may be combined. 
     EXPLANATION OF REFERENCES 
     
         
         
           
               10  Magnetic recording layer 
               11 ,  12  Magnetization fixing region 
               13  Domain wall moving region 
               13 A First magnetic domain 
               13 B Second magnetic domain 
               20  Non-magnetic layer 
               30  Ferromagnetic layer 
               30 A First surface 
               30 B Second surface 
               31  First region 
               32  Second region 
               33  Central region 
               34  Outer circumferential region 
               41  First conductive layer 
               42  Second conductive layer 
               51 ,  52 , In Insulating layer 
               100 ,  101  Magnetic domain wall moving element 
               200  Magnetic array 
             CL Common line 
             DW Domain wall 
             RL Read line 
             Sub Substrate 
             WL Write line