Patent Publication Number: US-2022231084-A1

Title: Magnetic domain wall moving element and magnetic recording array

Description:
TECHNICAL FIELD 
     The present invention relates to a magnetic domain wall moving element and a magnetic recording array. Priority is claimed on Japanese Patent Application No. 2019-092867, filed May 16, 2019, the content of which is incorporated herein by reference. 
     BACKGROUND ART 
     Attention is being focused on next-generation non-volatile memories that will replace flash memories and the like whose microfabrication has reached its limit. For example, a magnetoresistive random access memory (MRAM), a resistance random access memory (ReRAM), a phase change random access memory (PCRAM), and the like are known as next-generation non-volatile memories. 
     MRAM uses a change in resistance value caused by a change in a magnetization direction for data recording. In order to realize a larger capacitance of a recording memory, reduction in size of elements constituting the memory and multi-valued recording bits per element constituting the memory are being studied. 
     Patent Literature 1 describes a magnetic domain wall moving element in which multi-valued data can be recorded by moving a domain wall in a data recording layer. Patent Literature 1 describes that magnetization of a magnetization pinned region is formed by utilizing a difference in coercive force. 
     CITATION LIST 
     Patent Literature 
     [Patent Literature 1] 
     
         
         Japanese Patent No. 5397384 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     A magnetic recording layer in which a domain wall moves often has magnetization pinned regions at both ends in order to prevent the domain wall from reaching any one end and disappearing. When a domain wall intrudes into a magnetization pinned region, the domain wall may disappear. Since a magnetic domain wall moving element records data at a position of a domain wall, data cannot be recorded when the domain wall disappears. 
     The present invention has been made in view of the above problems, and provides a magnetic domain wall moving element and a magnetic recording array in which movement of a domain wall can easily be controlled. 
     Solution to Problem 
     (1) A magnetic domain wall moving element according to a first aspect includes a magnetic recording layer which extends in a first direction and includes a ferromagnetic material, and a first conductive layer and a second conductive layer which are separately connected to the magnetic recording layer, in which the first conductive layer includes a first layer that exhibits ferromagnetism and in contact with the magnetic recording layer, the first layer includes a mixing layer at an interface with the magnetic recording layer, a ferromagnetic material and a dissimilar metal are mixed in the mixing layer, and the dissimilar metal is a metal different from each of the ferromagnetic material that mainly constitutes the first layer and the ferromagnetic material that mainly constitutes the magnetic recording layer. 
     (2) In the magnetic domain wall moving element according to the above aspect, the first conductive layer may have a second layer that exhibits non-magnetic ferromagnetism and a third layer that exhibits ferromagnetism in order on a surface of the first layer opposite to the magnetic recording layer. 
     (3) In the magnetic domain wall moving element according to the above aspect, the dissimilar metal may be a non-magnetic metal. 
     (4) In the magnetic domain wall moving element according to the above aspect, a concentration of the dissimilar metal may be higher on a first surface of the mixing layer on a side closer to the magnetic recording layer than on a second surface opposite to the first surface. 
     (5) In the magnetic domain wall moving element according to the above aspect, the dissimilar metal has a concentration distribution in the first direction, and a first end of the mixing layer on a side closer to a center of the magnetic recording layer in the first direction has a higher concentration of the dissimilar metal than the second end opposite to the first end. 
     (6) In the magnetic domain wall moving element according to the above aspect, the dissimilar metal may be locally distributed in the mixing layer. 
     (7) In the magnetic domain wall moving element according to the above aspect, the mixing layer may include a first portion in which the dissimilar metal is locally distributed, and a thickness of the mixing layer may vary from place to place due to the first portion. 
     (8) In the magnetic domain wall moving element according to the above aspect, a surface of the mixing layer may be uneven in a laminating direction due to the first portion in which the dissimilar metal is locally distributed. 
     (9) In the magnetic domain wall moving element according to the above aspect, the magnetic recording layer may include a second mixing layer on a side opposite to a surface connected to the first conductive layer, the ferromagnetic material and the dissimilar metal included in the magnetic recording layer may be mixed in the second mixing layer, and the dissimilar metal may be a metal different from the ferromagnetic material that mainly constitutes the magnetic recording layer. 
     (10) In the magnetic domain wall moving element according to the above aspect, the second conductive layer may include a fourth layer that exhibits ferromagnetic in contact with the magnetic recording layer, the fourth layer may include a third mixing layer at an interface with the magnetic recording layer, a ferromagnetic material and a dissimilar metal may be mixed in the third mixing layer, and the dissimilar metal may be a metal different from each of the ferromagnetic material that mainly constitutes the fourth layer and the ferromagnetic material that mainly constitutes the magnetic recording layer. 
     (11) A magnetic domain wall moving element according to a second aspect includes a magnetic recording layer which extends in a first direction and includes a ferromagnetic material, and a first conductive layer and a second conductive layer which are separately connected to the magnetic recording layer, in which the first conductive layer includes a first layer that exhibits ferromagnetism and in contact with the magnetic recording layer, the first layer includes a mixing layer at an interface with the magnetic recording layer, a non-magnetic material and a ferromagnetic material are alternately laminated in the first layer, and the ferromagnetic material and the non-magnetic material are mixed in the mixing layer. 
     (12) The magnetic domain wall moving element according to the above aspect may further include a first ferromagnetic layer facing the magnetic recording layer, and a non-magnetic layer located between the first ferromagnetic layer and the magnetic recording layer. 
     (13) A magnetic recording array according to a third aspect includes a plurality of magnetic domain wall moving elements according to the above aspects. 
     Advantageous Effects of Invention 
     The magnetic domain wall moving element and the magnetic recording array according to the above aspects can easily control movement of a domain wall. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a configuration diagram of a magnetic recording array according to a first embodiment. 
         FIG. 2  is a cross-sectional view of a featured portion of the magnetic recording array according to the first embodiment. 
         FIG. 3  is a cross-sectional view of a magnetic domain wall moving element according to the first embodiment. 
         FIG. 4  is a cross-sectional view of a featured portion of the magnetic domain wall moving element according to the first embodiment. 
         FIG. 5  is a plan view of a mixing layer according to the first embodiment. 
         FIG. 6  is a cross-sectional view of the mixing layer according to the first embodiment. 
         FIG. 7  is a plan view of another example of the mixing layer according to the first embodiment. 
         FIG. 8  is a cross-sectional view of a featured portion of a magnetic domain wall moving element according to a second embodiment. 
         FIG. 9  is a cross-sectional view of a featured portion of a magnetic domain wall moving element according to a third embodiment. 
         FIG. 10  is a cross-sectional view of a featured portion of a magnetic domain wall moving element according to a fourth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, the present embodiment will be described in detail with reference to the drawings as appropriate. In the drawings used in the following description, featured portions may be shown enlarged for convenience in order to make features of the present invention easy to understand, and dimensional ratios and the like of respective constituent elements may differ from actual ones. Materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited thereto and can be appropriately modified and carried out within the range in which the effects of the present invention can be achieved. 
     First, directions will be defined. A +x direction, a −x direction, a +y direction, and a −y direction are directions substantially parallel to one surface of a substrate Sub (see  FIG. 2 ), which will be described later. The +x direction is a direction in which a magnetic recording layer  20  extends, which will be described later, and is a direction from a first conductive layer  40  toward a second conductive layer  50 , which will be described later. The −x direction is a direction opposite to the +x direction. In a case in which the +x direction and the −x direction are not distinguished, they are simply referred to as an “x direction.” The x direction is an example of a first direction. The +y direction is one direction orthogonal to the x direction. The −y direction is a direction opposite to the +y direction. In a case in which the +y direction and the −y direction are not distinguished, they are simply referred to as a “y direction.” A +z direction is a direction from the substrate Sub, which will be described later, toward a magnetic domain wall moving element  100 . A −z direction is a direction opposite to the +z direction. In a case in which the +z direction and the −z direction are not distinguished, they are simply referred to as a “z direction.” The z direction is an example of a laminating direction. Further, in the present specification, “extending in the x direction” means that, for example, a dimension in the x direction is larger than the smallest dimension among dimensions in the x direction, the y direction, and the z direction. The same applies to cases of extending in other directions. 
     First Embodiment 
       FIG. 1  is a configuration diagram of a magnetic recording array according to a first embodiment. A magnetic recording array  200  includes a plurality of magnetic domain wall moving elements  100 , a plurality of first wirings Wp 1  to Wpn, a plurality of second wirings Cm 1  to Cmn, a plurality of third wirings Rp 1  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, for a magnetic memory, a product-sum calculator, and a neuromorphic device. 
     &lt;First Wirings, Second Wirings, and Third Wirings&gt; 
     The first wirings Wp 1  to Wpn are write wirings, respectively. The write wirings are used when data is written. Each of the first wirings Wp 1  to Wpn electrically connects a power supply to one or more magnetic domain wall moving elements  100 . The power supply is connected to one end of the magnetic recording array  200  during use. 
     The second wirings Cm 1  to Cmn are common wirings, respectively. The common wirings are used both when data is written and when data is read. Each of the second wirings Cm 1  to Cmn electrically connects a reference potential to one or more magnetic domain wall moving elements  100 . The reference potential is, for example, a ground. The second wirings Cm 1  to Cmn may be provided for 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 , respectively. 
     The third wirings Rp 1  to Rpn are read wirings, respectively. The read wirings are used when data is read. Each of the third wirings Rp 1  to Rpn electrically connects the power supply to one or more magnetic domain wall moving elements  100 . The power supply is connected to one end of the magnetic recording array  200  during use. 
     &lt;First Switching Elements, Second Switching Elements, and Third Switching Elements&gt; 
     The first switching element  110 , the second switching element  120 , and the third switching element  130  shown in  FIG. 1  are connected to each of the plurality of magnetic domain wall moving elements  100 . A device in which switching elements are connected to the magnetic domain wall moving element  100  is referred to as a semiconductor device. The first switching element  110  is connected between the magnetic domain wall moving element  100  and the first wiring Wp 1  to Wpn. The second switching element  120  is connected between the magnetic domain wall moving element  100  and the second wiring Cm 1  to Cmn. The third switching element  130  is connected between the magnetic domain wall moving element  100  and the third wiring Rp 1  to Rpn. 
     When the first switching element  110  and the second switching element  120  are turned on, write currents flow between one of the first wirings Wp 1  to Wpn and one of the second wirings Cm 1  to Cmn connected to predetermined magnetic domain wall moving element  100 . When the first switching element  110  and the third switching element  130  are turned on, read currents flow between one of the second wirings Cm 1  to Cmn and one of the third wirings Rp 1  to Rpn connected to predetermined magnetic domain wall moving element  100 . 
     The first switching elements  110 , the second switching elements  120 , and the third switching elements  130  are elements that control a flow of an electric current. The first switching elements  110 , the second switching elements  120 , and the third switching elements  130  are, for example, elements that utilize a phase change of a crystal layer, such as transistors and Ovonic threshold switches (OTSs), elements that utilize a change in band structure, such as metal-insulator transition (MIT) switches, elements that utilize a breakdown voltage, such as Zener diodes and avalanche diodes, and elements whose conductivity changes with a change in atomic position. 
     Any one of the first switching elements  110 , the second switching elements  120 , and the third switching elements  130  may be shared by the magnetic domain wall moving elements  100  connected to the same wirings. For example, in a case in which the first switching elements  110  are shared, one of the first switching elements  110  is disposed upstream from the first wirings Wp 1  to Wpn. For example, in a case in which the second switching elements  120  are shared, one of the second switching elements  120  is disposed upstream from the second wirings Cm 1  to Cmn. For example, in a case in which the third switching elements  130  are shared, one of the third switching elements  130  is disposed upstream from the third wirings Rp 1  to Rpn. 
       FIG. 2  is a cross-sectional view of a featured portion of the magnetic recording array  200  according to the first embodiment.  FIG. 2  shows a cross-section of one magnetic domain wall moving element  100  in  FIG. 1  cut along an xz plane passing through a center of a width of the magnetic recording layer  20  in the y direction. 
     The first switching element  110  and the second switching element  120  shown in  FIG. 2  are transistors Tr. The transistors Tr each have a gate electrode G, a gate insulating film GI, and a source region S and a drain region D that are formed on the substrate Sub. The substrate Sub is, for example, a semiconductor substrate. The third switching element  130  is electrically connected to an electrode E and is located, for example, in a depth direction (−y direction) of the paper surface. 
     Each of the transistors Tr and the magnetic domain wall moving element  100  are electrically connected to each other via connection wirings Cw. The connection wirings Cw include a conductive material. The connection wirings Cw extend in the z direction. The connection wirings Cw are, for example, via wirings formed in opening portions of an insulating layer  90 . 
     The magnetic domain wall moving element  100  and the transistors Tr are electrically separated by the insulating layer  90  except for the connection wirings Cw. The insulating layer  90  is an insulating layer that insulates between wirings of multilayer wirings and between elements. The insulating layer  90  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 Moving Element” 
       FIG. 3  is a cross-sectional view of the magnetic domain wall moving element  100  according to the first embodiment. The magnetic domain wall moving element  100  has a first ferromagnetic layer  10 , a magnetic recording layer  20 , a non-magnetic layer  30 , a first conductive layer  40 , and a second conductive layer  50 .  FIG. 3  is a cross-sectional view of the magnetic domain wall moving element  100  cut along the xz plane passing through the center of the magnetic recording layer  20  in the y direction.  FIG. 3  is an enlarged view of a portion of  FIG. 2 , and a periphery of the magnetic domain wall moving element  100  is covered with the insulating layer  90 . The magnetic domain wall moving element  100  is used as a storage element as an example. 
     “First Ferromagnetic Layer” 
     The first ferromagnetic layer  10  faces the non-magnetic layer  30 . The first ferromagnetic layer  10  is, for example, in contact with the non-magnetic layer  30 . The first ferromagnetic layer  10  has a magnetization M 10  oriented in one direction. The direction in which the magnetization M 10  of the first ferromagnetic layer  10  is oriented is less likely to change than that of magnetization of the magnetic recording layer  20  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 polarization current. The first ferromagnetic layer  10  is sometimes called a magnetization pinned layer or a magnetization reference layer. The magnetization M 10  is oriented in the z direction, for example. 
     Hereinafter, an example in which the magnetization is oriented in the z direction will be described, but the magnetizations of the magnetic recording layer  20  and the first ferromagnetic layer  10  may be oriented in the x direction, or may be oriented in any direction in an xy plane. In a case in which the magnetizations are oriented in the z direction, power consumption and heat generation during operation of the magnetic domain wall moving element  100  are inhibited as compared with the case in which the magnetizations are oriented in the xy plane. Also, in the case in which the magnetizations are oriented in the z direction, a movement width of a domain wall  27  deceases when a pulse current of the same intensity is applied as compared with the case in which the magnetizations are oriented in the xy plane. On the other hand, in the case in which the magnetizations are oriented in any direction in the xy plane, a magnetic resistance change width (MR ratio) of the magnetic domain wall moving element  100  increases as compared with the case in which the magnetizations are oriented in the z direction. 
     The first ferromagnetic layer  10  includes a ferromagnetic material. The ferromagnetic material constituting the first ferromagnetic layer  10  is, for example, a metal selected from the group consisting of Cr, Mn, Co, Fe and Ni, an alloy including one or more species of these metals, an alloy including these metals and at least one or more species of elements of B, C, and N, or the like. The first ferromagnetic layer  10  is, for example, Co—Fe, Co—Fe—B, or Ni—Fe. 
     The material constituting the first ferromagnetic layer  10  may be a Heusler alloy. A Heusler alloy is a half metal and has high spin polarizability. A Heusler alloy is an intermetallic compound having a chemical composition of XYZ or X 2 YZ, in which 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 of the Mn, V, Cr or Ti group or an elemental species of X, and Z is a typical element of groups III to 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. 
     In a case in which a magnetization easy axis of the first ferromagnetic layer  10  is in the z direction (it is formed as a perpendicular magnetization film), a film thickness of the first ferromagnetic layer  10  is preferably 1.5 nm or less, more preferably 1.0 nm or less. When the thickness of the first ferromagnetic layer  10  decreases, vertical magnetic anisotropy (interfacial perpendicular magnetic anisotropy) is added to the first ferromagnetic layer  10  at an interface between the first ferromagnetic layer  10  and another layer (the non-magnetic layer  30 ), and the magnetization of the first ferromagnetic layer  10  is easily oriented in the z direction. 
     In the case in which the magnetization easy axis of the first ferromagnetic layer  10  is in the z direction (it is formed as the perpendicular magnetization film), it is preferable that the first ferromagnetic layer  10  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 it is more preferable to insert an intermediate layer selected from the group consisting of Ir and Ru into any position of the laminate. Vertical magnetic anisotropy can be made stronger by laminating the ferromagnetic material and the non-magnetic material, and the magnetization of the first ferromagnetic layer  10  can be easily oriented in the z direction by inserting the intermediate layer. 
     An antiferromagnetic layer may be provided on a surface of the first ferromagnetic layer  10  opposite to the non-magnetic layer  30  via a spacer layer. The first ferromagnetic layer  10 , the spacer layer, and the antiferromagnetic layer have a synthetic antiferromagnetic structure (SAF structure). The synthetic antiferromagnetic structure consists of two magnetic layers sandwiching a non-magnetic layer. The first ferromagnetic layer  10  and the antiferromagnetic layer are antiferromagnetically coupled, and thus a coercive force of the first ferromagnetic layer  10  increases as compared with the case in which the anti ferromagnetic layer is not provided. 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. 
     “Magnetic Recording Layer” 
     The magnetic recording layer  20  extends in the x direction. The magnetic recording layer  20  is, for example, a rectangle having a major axis in the x direction and a minor axis in the y direction in a plan view seen in the z direction. The magnetic recording layer  20  is a magnetic layer facing the first ferromagnetic layer  10  with the non-magnetic layer  30  interposed therebetween. The magnetic recording layer  20  extends over the first conductive layer  40  and the second conductive layer  50 . 
     The magnetic recording layer  20  is a layer capable of magnetically recording information by changing an internal magnetic state thereof. The magnetic recording layer  20  has a first magnetic domain  28  and a second magnetic domain  29  therein. A magnetization M 28  of the first magnetic domain  28  and a magnetization M 29  of the second magnetic domain  29  are oriented in opposite directions, for example. A boundary between the first magnetic domain  28  and the second magnetic domain  29  is the domain wall  27 . The magnetic recording layer  20  can have the domain wall  27  therein. In the magnetic recording layer  20  shown in  FIG. 3 , the magnetization M 28  of the first magnetic domain  28  is oriented in the +z direction, and the magnetization M 29  of the second magnetic domain  29  is oriented in the −z direction. 
     Magnetizations of a portion that overlaps the first conductive layer  40  and a portion that overlaps the second conductive layer  50  in the z direction of the magnetic recording layer  20  are fixed in one direction. The portion that overlaps the first conductive layer  40  and the portion that overlaps the second conductive layer  50  in the z direction of the magnetic recording layer  20  may be referred to as a magnetization pinned region. The portion that overlaps the first conductive layer  40  in the z direction of the magnetic recording layer  20  is fixed, for example, in the +z direction, and the portion that overlaps the second conductive layer  50  in the z direction of the magnetic recording layer  20  is fixed, for example, in the −z direction. Unless an excessive external force is applied, the domain wall  27  moves in a portion that does not overlap the first conductive layer  40  and the second conductive layer  50  in the z direction of the magnetic recording layer  20 . 
     The magnetic domain wall moving element  100  can record data in multi-value or continuously depending on a position of the domain wall  27  of the magnetic recording layer  20 . The data recorded on the magnetic recording layer  20  is read out as a resistance change value of the magnetic domain wall moving element  100  when a read-out current is applied. 
     Proportions of the first magnetic domain  28  and the second magnetic domain  29  in the magnetic recording layer  20  change as the domain wall  27  moves. The magnetization M 10  of the first ferromagnetic layer  10  is, for example, in the same direction as (parallel to) the magnetization M 28  of the first magnetic domain  28 , and in the opposite direction (antiparallel) to the magnetization M 29  of the second magnetic domain  29 . When the domain wall  27  moves in the +x direction and an area of the first magnetic domain  28  in the portion overlapping the first ferromagnetic layer  10  in a plan view seen in the z direction increases, a resistance value of the magnetic domain wall moving element  100  decreases. On the other hand, when the domain wall  27  moves in the −x direction and an area of the second magnetic domain  29  in the portion overlapping the first ferromagnetic layer  10  in a plan view seen in the z direction increases, the resistance value of the magnetic domain wall moving element  100  increases. 
     The domain wall  27  moves by passing a write current in the x direction of the magnetic recording layer  20  or applying an external magnetic field. For example, when a write current (for example, a current pulse) is applied in the +x direction of the magnetic recording layer  20 , electrons flow in the −x direction opposite to the current, and thus the domain wall  27  moves in the −x direction. In a case in which a current flows from the first magnetic domain  28  to the second magnetic domain  29 , spin-polarized electrons in the second magnetic domain  29  reverse the magnetization M 28  in the first magnetic domain  28 . When the magnetization M 28  of the first magnetic domain  28  is reversed, the domain wall  27  moves in the −x direction. 
     The magnetic recording layer  20  is made of a magnetic material. The magnetic material constituting the magnetic recording layer  20  is, for example, a metal selected from the group consisting of Cr, Mn, Co, Fe and Ni, an alloy including one or more species of these metals, an alloy including these metals and at least one or more species of elements of B, C, and N, or the like. Specifically, the magnetic material constituting the magnetic recording layer  20  is, for example, Co—Fe, Co—Fe—B, or Ni—Fe. 
     The magnetic recording layer  20  may have at least one element selected from the group consisting of Co, Ni, Pt, Pd, Gd, Tb, Mn, Ge, and Ga. The magnetic recording layer  20  is, for example, a laminated film of Co and Ni, a laminated film of Co and Pt, or a laminated film of Co and Pd. Also, for example, the magnetic recording layer  20  may include a MnGa-based material, a GdCo-based material, or a TbCo-based material. Because ferromagnetic materials such as the MnGa-based material, the GdCo-based material, and the TbCo-based material have a small saturation magnetization, a threshold current required to move the domain wall decreases. Further, because the laminated film of Co and Ni, the laminated film of Co and Pt, and the laminated film of Co and Pd have a large coercive force, a moving speed of the domain wall decreases. 
     “Non-Magnetic Layer” 
     The non-magnetic layer  30  is located between the first ferromagnetic layer  10  and the magnetic recording layer  20 . The non-magnetic layer  30  is laminated on one surface of the magnetic recording layer  20 . 
     The non-magnetic layer  30  is made of, for example, a non-magnetic insulator, semiconductor or metal. The non-magnetic insulator is, for example, Al 2 O 3 , SiO 2 , MgO, MgAl 2 O 4 , or a material in which Al, Si, and Mg in some of these are replaced with Zn, Be, and the like. These materials have a large bandgap and excellent insulating properties. In a case in which the non-magnetic layer  30  is made of a non-magnetic insulator, the non-magnetic layer  30  is a tunnel barrier layer. The non-magnetic metal is, for example, Cu, Au, Ag, or the like. The non-magnetic semiconductor is, for example, Si, Ge, CuInSe 2 , CuGaSe 2 , Cu(In,Ga)Se 2 , or the like. 
     A thickness of the non-magnetic layer  30  is preferably 20 Å or more, and more preferably 30 Å or more. When the thickness of the non-magnetic layer  30  is large, 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 5  Ωμm 2  or more, and more preferably 1×10 6  Ωμm 2  or more. The resistance area product (RA) of the magnetic domain wall moving element  100  is represented by a product of an elemental resistance of one magnetic domain wall moving element  100  and an elemental cross-sectional area (an area of a cut surface obtained by cutting the non-magnetic layer  30  on the xy plane) of the magnetic domain wall moving element  100 . 
     “First Conductive Layer” 
     The first conductive layer  40  has a first layer  41 , a second layer  42 , and a third layer  43 . The first layer  41  and the third layer  43  are ferromagnetic layers. The second layer  42  is a non-magnetic layer. The first layer  41  and the third layer  43  are antiferromagnetically coupled with the second layer  42  interposed therebetween. The first conductive layer  40  has an SAF structure. Magnetization M 41  of the first layer  41  is oriented in the +z direction, for example, and magnetization M 43  of the third layer  43  is oriented in the −z direction, for example. The second layer  42  may be referred to as an intermediate layer, an insertion layer, a magnetic coupling layer, or the like. 
     The same material as the first ferromagnetic layer  10  can be used for the first layer  41  and the third layer  43 . The first layer  41  and the third layer  43  are made of, for example, a laminated film of Co and Ni, a laminated film of Co and Pd, a laminated film of Co and Pt, a CoCrPt alloy, a GdFe alloy, a TbCo alloy, or the like. The second layer  42  includes, for example, at least one selected from the group consisting of Ru, Ir, and Rh. A thickness of the second layer  42  is, for example, 0.1 nm to 10 nm. 
       FIG. 4  is a cross-sectional view of a main portion of the magnetic domain wall moving element  100  according to the first embodiment.  FIG. 4  is an enlarged view of the vicinity of the first layer  41  of the first conductive layer  40  in  FIG. 3 . The first layer  41  has a main portion  411  and a mixing layer  412 . The main portion  411  is located at a position separated from the magnetic recording layer  20  further than the mixing layer  412 . The mixing layer  412  is located at an interface of the first layer  41  on a magnetic recording layer  20  side. The main portion  411  is a main portion of the first layer  41 . The mixing layer  412  is a layer in which a ferromagnetic material included in the first layer  41  and a dissimilar metal are mixed. For example, in a case in which the first layer  41  is a laminated film in which Co and Pt are alternately laminated, the ferromagnetic material included in the first layer  41  is Co, which is a main ferromagnetic material constituting the first layer  41 . 
     The dissimilar metal may be dispersed in the mixing layer  412  or locally distributed. The dissimilar metal is a metal different from each of the ferromagnetic material that mainly constitutes the first layer  41  and the ferromagnetic material that mainly constitutes the magnetic recording layer  20 . The dissimilar metal is, for example, a non-magnetic metal. When the dissimilar metal is a non-magnetic metal, it is possible to prevent pinning of the magnetization of the magnetic recording layer  20  from being disturbed at a position at which it overlaps the first conductive layer  40  in the z direction. The dissimilar metal includes, for example, at least one selected from the group consisting of Ru, Ir, Ta, and Rh. 
     A concentration of the dissimilar metal in the mixing layer  412  is, for example, higher on a first surface  412   a  than on a second surface  412   b . The first surface  412   a  is a surface of the mixing layer  412  on the magnetic recording layer  20  side, and the second surface  412   b  is a surface opposite to the first surface  412   a . The concentration of the dissimilar metal in the mixing layer  412  decreases as it approaches the second surface  412   b  from the first surface  412   a , for example. When the concentration of the dissimilar metal on the first surface  412   a  is higher than that on the second surface  412   b , intrusion of the domain wall  27  into the position at which it overlaps the first conductive layer  40  in the z direction of the magnetic recording layer  20  can be further inhibited, and deterioration of magnetic characteristics of the first layer  41  can be inhibited. 
     The concentration of the dissimilar metal in the mixing layer  412  is, for example, higher at a first end  412   c  than at a second end  412   d . The first end  412   c  is an end portion of the mixing layer  412  on a side closer to a center of the magnetic recording layer  20  in the x direction. The second end  412   d  is an end portion of the mixing layer  412  opposite to the first end  412   c . The second end  412   d  is an end portion of the mixing layer  412  on a side far from the center of the magnetic recording layer  20  in the x direction. The concentration of the dissimilar metal in the mixing layer  412  decreases as it approaches the second end  412   d  from the first end  412   c , for example. When the concentration of the dissimilar metal at the first end  412   c  is high, it becomes difficult for the domain wall  27  to intrude into the magnetization pinned region. Further, by lowering the concentration of the dissimilar metal at the second end  412   d , it is possible to inhibit deterioration of magnetic characteristics of the magnetic domain wall moving element  100 . 
     The mixing layer  412  is formed by sputtering the dissimilar metal on a surface of the first conductive layer  40  on the magnetic recording layer  20  side. The dissimilar metal is laminated to such a thickness that the dissimilar metal does not form a continuous layer. A thickness that does not form a continuous layer is approximately three times or less an atomic diameter of the dissimilar metal. The mixing layer  412  is formed by driving the dissimilar metal into the first layer  41 . 
       FIG. 5  is a plan view of an example of the mixing layer  412  according to the first embodiment.  FIG. 6  is a cross-sectional view of the example of the mixing layer  412  according to the first embodiment.  FIGS. 5 and 6  are examples in which the dissimilar metal is locally distributed in the mixing layer  412 . The mixing layer  412  is divided into, for example, a first portion A 1  and a second portion A 2 . The first portion A 1  is a portion in which the dissimilar metal is locally distributed. The second portion A 2  is a portion other than the dissimilar metal and is made of the same material as the main portion  411 . 
     The first portion A 1  is formed by, for example, driving the dissimilar metal into the first layer  41 . A thickness of the first portion A 1  in the z direction differs depending on a location in the xy plane of the mixing layer  412 , for example. The thickness of the first portion A 1  varies from place to place, for example, depending on an amount of energy of the dissimilar metal when being driven into the first layer  41 . A thickness of the mixing layer  412  varies from place to place due to the first portion A 1 . 
     Surfaces of the first portion A 1  are curved due to a difference in surface tension with an adjacent material, for example. Among the surfaces of the first portion A 1 , a surface protruding in the +z direction from an interface between the second portion A 2  and the magnetic recording layer  20  is referred to as a first surface A 1   a , and a surface protruding in the −z direction therefrom is referred to as a second surface A 1   b . The first surface A 1   a  protrudes from a surface A 2   a  of the second portion A 2  in the +z direction, and thus the first surface  412   a  of the mixing layer  412  becomes uneven in the z direction. For example, the dissimilar metal is driven into the first layer  41 , whereby the second surface A 1   b  protrudes from the surface A 2   a  of the second portion A 2  in the −z direction. 
     “Second Conductive Layer” 
     The second conductive layer  50  has a fourth layer  51 , a fifth layer  52 , and a sixth layer  53 . The fourth layer  51  and the sixth layer  53  are ferromagnetic layers. The fifth layer  52  is a non-magnetic layer. The fourth layer  51  and the sixth layer  53  are antiferromagnetically coupled with the fifth layer  52  interposed therebetween. The second conductive layer  50  has an SAF structure. Magnetization M 51  of the fourth layer  51  is oriented in the −z direction, for example, and magnetization M 53  of the sixth layer  53  is oriented in the +z direction, for example. The fifth layer  52  may be referred to as an intermediate layer, an insertion layer, a magnetic coupling layer, or the like. 
     The same materials as those of the first layer  41  and the third layer  43  can be used for the fourth layer  51  and the sixth layer  53 . The same material as that of the second layer  42  can be used for the fifth layer  52 . 
     The fourth layer  51  preferably has a mixing layer at an interface with the magnetic recording layer  20 . The mixing layer located at the interface between the fourth layer  51  and the magnetic recording layer  20  is an example of the third mixing layer. The mixing layer located at the interface between the fourth layer  51  and the magnetic recording layer  20  is a layer in which a ferromagnetic material and a dissimilar metal included in the fourth layer  51  are mixed. The dissimilar metal is a metal different from the ferromagnetic material that mainly constitutes each of the fourth layer  51  and the magnetic recording layer  20 . The dissimilar metal is, for example, a non-magnetic metal. The dissimilar metal includes, for example, at least one selected from the group consisting of Ru, Ir, Ta, and Rh. The dissimilar metal may be dispersed in the mixing layer or locally distributed. 
     The magnetization directions of the first ferromagnetic layer  10 , the magnetic recording layer  20 , the first conductive layer  40 , and the second conductive layer  50  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 performed by using a magneto optical effect (magnetic Kerr effect) in which linearly polarized light is incident on a measurement target object and rotation in a polarization direction thereof occurs. 
     Next, a method for manufacturing the magnetic recording array  200  will be described. The magnetic recording array  200  is formed by a laminating step of each layer and a processing step of processing a portion of each layer into a predetermined 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 deposition method, or the like can be used. The processing of each layer can be performed by using photolithography or the like. 
     First, impurities are doped at predetermined positions on the substrate Sub to form the source regions S and the drain regions D. Next, the gate insulating films GI and the gate electrodes G are formed between the source regions S and the drain regions D. The source regions S, the drain regions D, the gate insulating films GI, and the gate electrodes G serve as the transistors Tr. 
     Next, the insulating layer  90  is formed to cover the transistors Tr. Further, the connection wirings Cw are formed by forming the opening portions in the insulating layer  90  and filling the opening portion with a conductor. The first wirings Wp and the second wirings Cm are formed by laminating the insulating layer  90  to a predetermined thickness, forming grooves in the insulating layer  90 , and filling the grooves with the conductor. 
     The first conductive layer  40  and the second conductive layer  50  can be formed by, for example, laminating a ferromagnetic layer, a non-magnetic layer, and a ferromagnetic layer in order on one surface of the insulating layer  90  and the connection wirings Cw and removing portions other than portions that will be the first conductive layer  40  and the second conductive layer  50 . The removed portions are filled with, for example, the insulating layer  90 . The mixing layer can be formed, for example, by sputtering a dissimilar metal onto the first layer  41  and the fourth layer  51 . 
     Finally, the ferromagnetic layer, the non-magnetic layer, and the ferromagnetic layer are laminated in order over the first conductive layer  40  and the second conductive layer  50 , and processed into a predetermined shape, and thus the magnetic recording layer  20 , the non-magnetic layer  30 , and the first ferromagnetic layer  10  are formed. 
     The magnetic domain wall moving element  100  according to the first embodiment can prevent the domain wall  27  from intruding at the positions (magnetization pinned regions) in which it overlaps the first conductive layer  40  and the second conductive layer  50  of the magnetic recording layer  20  in the z direction. When the domain wall  27  reaches end portions of the magnetic recording layer  20 , the domain wall  27  disappears, and data may not be recorded. By inhibiting the intrusion of the domain wall  27  into the positions in which it overlaps the first conductive layer  40  and the second conductive layer  50  in the z direction, data can be easily written and read. 
     The mixing layer  412  serves as a pinning site for the domain wall  27 . The pinning site is a portion at which the magnetization becomes difficult to move. The pinning site affects an adjacent region (the magnetic recording layer  20 ) and achieves an effect of pinning the magnetization more strongly. In the mixing layer  412 , due to dissipative presence of the dissimilar metal in the xy plane, energy potential in the xy plane is not uniform. When the dissimilar metal is locally distributed, a difference in energy potential within the xy plane increases. The domain wall  27  becomes difficult to move in a portion in which the energy potential is low, and the movement of the domain wall  27  is restricted. That is, the mixing layer  412  can prevent the domain wall  27  from intruding at the positions in which it overlaps the first conductive layer  40  and the second conductive layer  50  in the z direction. 
     In addition, generally, the magnitude of the magnetization is different for each region in different state due to crystal grains, a surface condition, a step, etching damage, etc. Accordingly, when the first surface  412   a  of the mixing layer  412  has unevenness, the magnetization of the magnetic recording layer  20  at the position at which it is in contact with the mixing layer  412  is more pinned, and it is possible to further prevent the domain wall  27  from intruding at the positions in which it overlaps the first conductive layer  40  and the second conductive layer  50  in the z direction. Further, when a dissimilar element is sputtered into the first layer  41  and the fourth layer  51 , the first layer  41  and the fourth layer  51  are damaged. Since a surface condition or the like of a damaged portion changes, the magnetization at a position at which the magnetic recording layer  20  is in contact with the mixing layer  412  is more strongly pinned. 
     Further, the mixing layer  412  is particularly useful when the first conductive layer  40  and the second conductive layer  50  have an SAF structure. In a case in which the first conductive layer  40  has an SAF structure, stability of the magnetizations M 41  and M 51  of the first layer  41  and the fourth layer  51  with respect to an external magnetic field increases, but stability with respect to an electric current degreases. In the case in which the first conductive layer  40  has an SAF structure, a magnetic field generated by the first layer  41  and a magnetic field generated by the third layer  43  are in a weakening relationship with each other, and saturated magnetization of the entire first conductive layer  40  decreases. When the saturation magnetization of the entire first conductive layer  40  decreases, a threshold current density of the magnetic recording layer  20  at the position at which it is in contact with the first conductive layer  40  decreases. The threshold current density is a current density that serves as a threshold at which the domain wall  27  starts to move in the magnetic recording layer  20 . In the case in which the first conductive layer  40  has an SAF structure, the threshold current density is reduced by an order of magnitude as compared with a case in which the first conductive layer  40  has only the first layer  41 . 
     The decrease in the threshold current density of the magnetic recording layer  20  at the position at which it is in contact with the first conductive layer  40  means that, when a current having the same current density is applied, the domain wall  27  easily intrudes into the position in which it overlaps the first conductive layer  40  in the z direction. That is, in the case in which the first conductive layer  40  has an SAF structure, the problem that the domain wall  27  intrudes into the position in which it overlaps the first conductive layer  40  in the z direction becomes a remarkable problem. Even in the case in which the first conductive layer  40  has an SAF structure, the mixing layer  412  can prevent the domain wall  27  from intruding into the position in which it overlaps the first conductive layer  40  in the z direction. 
     Although examples of the magnetic recording array  200  and the magnetic domain wall moving element  100  according to the first embodiment have been described in detail, the magnetic recording 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. 
     For example,  FIG. 7  is a plan view of another example of the mixing layer according to the first embodiment. In the mixing layer  413  shown in  FIG. 7 , the first portions A 1  and the second portions A 2  are alternately arranged in the x direction. The first portions A 1  and the second portions A 2  extend in the y direction. 
     The domain wall  27  moves in the x direction. When the mixing layer  413  has a potential distribution in the x direction, it is possible to efficiently inhibit the intrusion of the domain wall  27  into the positions in which it overlaps the first conductive layer  40  and the second conductive layer  50  in the z direction. The mixing layer  413  shown in  FIG. 7  can be formed, for example, by sputtering the dissimilar metal through a mask having opening portions and mask portions alternately in the x direction. Further, the mixing layer  413  can be formed by photolithography or the like. 
     Second Embodiment 
       FIG. 8  is a cross-sectional view of a featured portion of a magnetic domain wall moving element according to a second embodiment. The magnetic domain wall moving element shown in  FIG. 8  is different from the magnetic domain wall moving element shown in  FIG. 4  in that a mixing layer  21  is formed on a second surface  20   b  of the magnetic recording layer  20 . In  FIG. 8 , the same configurations as those in  FIG. 4  are denoted by the same reference numerals, and the description thereof will be omitted. 
     The mixing layer  21  is on the second surface  20   b  of the magnetic recording layer  20 . The second surface  20   b  is a surface on a side opposite to the first surface  20   a  in contact with the first conductive layer  40  of the magnetic recording layer  20 . The mixing layer  21  is an example of a second mixing layer. The mixing layer  21  is a layer in which a ferromagnetic material that mainly constitute the magnetic recording layer  20  and a dissimilar metal are mixed. The dissimilar metal may be dispersed in the mixing layer  21  or locally distributed. The dissimilar metal is a metal different from the ferromagnetic material that mainly constitutes the magnetic recording layers  20 . The dissimilar metal is, for example, a non-magnetic metal. The dissimilar metal includes, for example, at least one selected from the group consisting of Ru, Ir, Ta, and Rh. 
     Since the first conductive layer  40  has the mixing layer  412  in the magnetic domain wall moving element according to the second embodiment, it is possible to prevent the domain wall  27  from intruding at the positions in which it overlaps the first conductive layer  40  and the second conductive layer  50  in the z direction. Further, by having the mixing layer  21  on the surface opposite to the mixing layer  412 , the movement of the domain wall  27  can be further inhibited. 
     Third Embodiment 
       FIG. 9  is a cross-sectional view of a main portion of a magnetic domain wall moving element according to a third embodiment. The magnetic domain wall moving element shown in  FIG. 9  is different from the magnetic domain wall moving element shown in  FIG. 4  in configurations of a main portion  414  and a mixing layer  415  of the first layer  41 . In  FIG. 8 , the same configurations as those in  FIG. 4  are denoted by the same reference numerals, and the description thereof will be omitted. 
     The main portion  414  is located to be separated from the magnetic recording layer  20  further than the mixing layer  415 . The mixing layer  415  is located at the interface of the first layer  41  on the magnetic recording layer  20  side. A ferromagnetic material  414 A and a non-magnetic material  414 B are alternately laminated in the main portion  414 . In the mixing layer  415 , a ferromagnetic material  415 A and a non-magnetic material  415 B are alternately laminated, and a non-magnetic material  415 B is dispersed in the ferromagnetic material  415 A. The ferromagnetic materials  414 A and  415 A are, for example, Co, and the non-magnetic materials  414 B and  415 B are, for example, Pd, Pt, or Ni. 
     In the mixing layer  415 , the non-magnetic material  415 B is scattered in the ferromagnetic material  415 A, and thus the energy potential in the xy plane is not uniform. For that reason, the mixing layer  415  serves as a pinning site for the domain wall  27 . The mixing layer  415  inhibits intrusion of the domain wall  27  into the positions in which it overlaps the first conductive layer  40  and the second conductive layer  50  in the z direction. 
     Fourth Embodiment 
       FIG. 10  is a cross-sectional view of a main portion of a magnetic domain wall moving element according to a fourth embodiment. The magnetic domain wall moving element shown in  FIG. 10  is different from the magnetic domain wall moving element shown in  FIG. 4  in that the first conductive layer  40  is configured of only the first layer  41 . In  FIG. 10 , the same configurations as those in  FIG. 4  are denoted by the same reference numerals, and the description thereof will be omitted. 
     As described above, the magnetic domain wall moving element is particularly useful when the first conductive layer  40  has an SAF structure, but when a large external force is applied even in a case in which the first conductive layer  40  does not have an SAF structure, the domain wall  27  may intrude at the position in which it overlaps the first conductive layer  40 . The first layer  41  has the mixing layer  412 , and thus it is possible to prevent the domain wall  27  from intruding at the positions in which it overlaps the first conductive layer  40  and the second conductive layer  50  in the z direction. 
     Preferred embodiments of the present invention have been described above in detail, but the present invention is not limited to a specific embodiment, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. 
     For example, the characteristic configurations in the first to fourth embodiments may be combined. Further, the description of the above embodiments has been on the basis of the example in which both the first conductive layer  40  and the second conductive layer  50  have a mixing layer, but only the first conductive layer  40  may have a mixing layer. 
     REFERENCE SIGNS LIST 
     
         
         
           
               10  First ferromagnetic layer 
               20  Magnetic recording layer 
               20   a ,  412   a , First surface 
               20   b ,  412   b , Second surface 
               412   c  First end 
               412   d  Second end 
               21 ,  412 ,  413 ,  415  Mixing layer 
               27  Domain wall 
               28  First magnetic domain 
               29  Second magnetic domain 
               30  Non-magnetic layer 
               40  First conductive layer 
               41  First layer 
               42  Second layer 
               43  Third layer 
               50  Second conductive layer 
               51  Fourth layer 
               52  Fifth layer 
               53  Sixth layer 
               90  Insulating layer 
               100  Magnetic domain wall moving element 
               110  First switching element 
               120  Second switching element 
               130  Third switching element 
               200  Magnetic recording array 
               411 , 414  Main portion 
               414 A,  415 A Ferromagnetic material 
               414 B,  415 B Non-magnetic material 
             A 1  First portion 
             A 2  Second portion 
             A 1   a  First surface 
             A 1   b  Second surface