JPWO2009019948A1 - Magnetic recording apparatus and magnetization fixing method - Google Patents

Abstract

The magnetic recording device includes a magnetic recording layer that is a ferromagnetic layer having perpendicular magnetic anisotropy. The magnetic recording layer includes a magnetization reversal region, a first magnetization fixed region that is connected to the first boundary of the magnetization reversal region and the magnetization direction is fixed in the first direction, and a second magnetization boundary that is connected to the second boundary of the magnetization reversal region. A second magnetization fixed region whose direction is fixed in a second direction opposite to the first direction. Consider the sign of the slope of the tangent to the periphery of the magnetic recording layer in the plane on which the magnetic recording layer is formed. At this time, the majority of the above-mentioned sign relating to the first magnetization fixed region is the opposite of the majority of the above-mentioned sign relating to the second magnetization fixed region.

Description

  The present invention relates to a magnetic recording apparatus exemplified by a magnetic random access memory. In particular, the present invention relates to a magnetic recording apparatus including a magnetic recording layer having perpendicular magnetic anisotropy, and a magnetization fixing method in the magnetic recording apparatus.

  Magnetic random access memory (MRAM) is a promising nonvolatile memory from the viewpoint of high integration and high-speed operation. In the MRAM, a magnetoresistive element exhibiting a “magnetoresistance effect” such as a TMR (Tunnel MagnetoResistance) effect is used. In the magnetoresistive element, for example, a magnetic tunnel junction (MTJ: Magnetic Tunnel Junction) in which a tunnel barrier layer is sandwiched between two ferromagnetic layers is formed. The two ferromagnetic layers are composed of a magnetization fixed layer (pinned layer) whose magnetization direction is fixed and a magnetization free layer (free layer) whose magnetization direction can be reversed.

  The resistance value (R + ΔR) of the MTJ when the magnetization directions of the pinned layer and the free layer are “anti-parallel” is larger than the resistance value (R) when they are “parallel” due to the magnetoresistance effect. It is known. The MRAM uses the magnetoresistive element having the MTJ as a memory cell, and stores data in a nonvolatile manner by utilizing the change in the resistance value. For example, the antiparallel state is associated with data “1”, and the parallel state is associated with data “0”. Data is written to the memory cell by reversing the magnetization direction of the free layer.

  Conventionally, “asteroid method” and “toggle method” are known as methods of writing data to the MRAM. According to these write methods, the reversal magnetic field necessary for reversing the magnetization of the free layer increases in inverse proportion to the memory cell size. That is, the write current tends to increase as the memory cell is miniaturized.

  A “spin transfer method” has been proposed as a write method capable of suppressing an increase in write current due to miniaturization (for example, Japanese Patent Laid-Open No. 2005-93488, JC Slonczewski, “Current-driven”). excitation of magnetic multilayers ", Journal of Magnetism and Magnetic Materials, 159, L1-L7, 1996.). According to the spin injection method, a spin-polarized current is injected into the ferromagnetic conductor, and the magnetization is reversed by a direct interaction between the spin of the conduction electron carrying the current and the magnetic moment of the conductor. (Hereinafter referred to as “Spin Transfer Magnetization Switching”).

  US Pat. No. 6,834,005 discloses a magnetic shift register utilizing spin injection. This magnetic shift register stores information using a domain wall in a magnetic material. In a magnetic material divided into a large number of regions (magnetic domains), a current is injected so as to pass through the domain wall, and the domain wall is moved by the current. The magnetization direction of each region is treated as recorded data. Such a magnetic shift register is used, for example, for recording a large amount of serial data. The movement of domain walls in magnetic materials is also described in Yamaguchi et al., “Real-Space Observation of Current-Driven Domain Wall Motion in Submicron Magnetic Wires”, PRL, Vol. 92, pp. 077205-1-4, 2004. It has been reported.

  “Domain wall motion type MRAM” using such current-driven domain wall motion by spin injection is disclosed in, for example, Japanese Patent Laid-Open Nos. 2005-191032, 2006-005308, and Japanese Patent Laid-Open No. 2006-005308. 2006-269885, JP-A-2006-303159, International Publication WO / 2007/020823, and Numata et al., "Magnetic Configuration of A New Memory Cell Utilizing Domain Wall Motion", Intermag 2006 Digest, HQ-03 .It is described in.

  An MRAM described in Japanese Patent Application Laid-Open No. 2005-191032 includes a magnetization fixed layer in which magnetization is fixed, a tunnel insulating layer stacked on the magnetization fixed layer, and a magnetic recording layer stacked on the tunnel insulating layer. . FIG. 1 shows the structure of the magnetic recording layer. In FIG. 1, the magnetic recording layer has a linear shape. Specifically, the magnetic recording layer includes a junction 103 overlapping the tunnel insulating layer and the magnetization fixed layer, a constriction 104 adjacent to both ends of the junction 103, and a pair of magnetization fixed portions 101 formed adjacent to the constriction 104. , 102. The pair of magnetization fixed portions 101 and 102 are provided with fixed magnetizations in opposite directions in the plane. The domain wall can be moved in the junction 103 by passing a write current in a direction corresponding to the write data between the magnetization fixed portions 101 and 102.

  FIG. 2 shows a magnetic recording layer of a magnetic memory cell described in International Publication WO / 2007/020823 and Numata et al., “Magnetic Configuration of A New Memory Cell Utilizing Domain Wall Motion”, Intermag 2006 Digest, HQ-03. The structure of is shown. This magnetic recording layer has a U-shape. Specifically, the magnetic recording layer has a first magnetization fixed region 111, a second magnetization fixed region 112, and a magnetization switching region 113. The magnetization switching region 113 overlaps the pinned layer 130. The magnetization fixed regions 111 and 112 are formed so as to extend in the Y direction, and their magnetization directions are fixed in the same direction. On the other hand, the magnetization switching region 113 is formed so as to extend in the X direction and has reversible magnetization. Therefore, the domain wall is formed at the boundary B1 between the first magnetization fixed region 111 and the magnetization switching region 113 or at the boundary B2 between the second magnetization fixed region 112 and the magnetization switching region 113. The domain wall can be moved in the magnetization switching region 113 by flowing a write current in a direction corresponding to the write data between the magnetization fixed regions 111 and 112.

  In the structure shown in FIG. 2, the magnetization state is initialized as follows. For example, an initialization magnetic field having a sufficient magnitude in the direction of 45 degrees obliquely in the XY plane is applied. After the application of the initial magnetic field is stopped, the magnetizations of the magnetization fixed regions 111 and 112 face the + Y direction, and the magnetization of the magnetization switching region 113 faces the + X direction. In this way, a state in which the domain wall is formed at the boundary B1 is realized.

In the MRAM using the above-described current-driven domain wall motion, it is important to reduce the write current. For example, it has been reported that the minimum threshold current density required for domain wall motion is approximately 10 ⁸ A / cm ² (Yamaguchi et al., “Real-Space Observation of Current-Driven Domain Wall Motion in Submicron Magnetic Wires ", PRL, Vol. 92, pp. 077205-1-4, 2004. JP-A-2006-005308). When the width of the layer in which the domain wall motion occurs is 100 nm and the film thickness is 10 nm, the minimum required write current is 1 mA. In order to further reduce the write current, it is conceivable to reduce the film thickness. However, it has also been reported that the threshold current density required for domain wall motion increases as the film thickness decreases (for example, Yamaguchi et al., “Reduction of Threshold Current Density for Current-Driven Domain Wall Motion using Shape Control ", Japanese Journal of Applied Physics, vol.45, No.5A, pp.3850-3853, 2006.).

Ravelosona et al., "Threshold currents to move domain walls in films with perpendicular anisotropy", Applied Physics Letters, 90, 072508, 2007. describes domain wall motion in films with perpendicular magnetic anisotropy. Has been. In this document, it is reported that the threshold current density required for domain wall motion is on the order of 10 ⁶ A / cm ² . Therefore, it is expected that the write current is reduced by using a magnetic recording layer having perpendicular magnetic anisotropy.

  As described above, in the case of a magnetic film having perpendicular magnetic anisotropy (hereinafter referred to as “perpendicular magnetic film”), it is more effective in moving the domain wall than in the case of in-plane magnetic anisotropy. The required threshold current density is reduced. Therefore, in the domain wall motion type MRAM, it is expected that the write current is reduced by using the perpendicular magnetization film as the magnetic recording layer.

  Assume that a perpendicular magnetization film having perpendicular magnetic anisotropy is applied to the structure shown in FIG. FIG. 3A and FIG. 3B are a plan view and a cross-sectional view, respectively, showing the assumed structure of the magnetic recording layer. 3A and 3B, the magnetic recording layer is formed on the XY plane and has a linear shape. Specifically, the magnetic recording layer includes a joint portion 123, a constricted portion 124 adjacent to both ends of the joint portion 123, and a pair of magnetization fixed portions 121 and 122 formed adjacent to the constricted portion 124. The pair of magnetization fixed portions 121 and 122 are provided with fixed magnetizations in opposite directions. For example, the magnetizations of the magnetization fixed portions 121 and 122 are fixed in the + Z direction and the −Z direction perpendicular to the film surface, respectively. When the magnetization direction of the bonding portion 123 is in the −Z direction, the domain wall DW is formed in the constricted portion 124 between the bonding portion 123 and the magnetization fixed portion 121. On the other hand, when the magnetization direction of the bonding portion 123 is the + Z direction, the domain wall DW is formed in the constricted portion 124 between the bonding portion 123 and the magnetization fixed portion 122. The constricted part 124 works as a pin potential with respect to the domain wall DW.

  As described above, in order to realize the domain wall motion type MRAM, it is necessary to fix the magnetization direction of a predetermined region in the magnetic recording layer and generate the domain wall DW in the magnetic recording layer. Such processing is hereinafter referred to as “initialization”. It is important to easily and stably initialize the magnetic recording layer from the viewpoints of manufacturing cost and reliability.

  In the case of the structure shown in FIG. 1, the magnetic recording layer has in-plane magnetic anisotropy, and it is necessary to fix the magnetization of the magnetization fixed portions 101 and 102 in the opposite direction along the X axis. . However, it is generally difficult to fix the magnetization in the opposite direction. However, in the case of the U-shaped structure shown in FIG. 2, the magnetization of the magnetization fixed regions 111 and 112 is fixed in the same direction along the Y axis, so that the initialization of the magnetic recording layer is relatively easy. is there.

  On the other hand, in the case of the structure shown in FIGS. 3A and 3B, the magnetic recording layer has perpendicular magnetic anisotropy. In this case, it is necessary to fix the magnetization of the magnetization fixing portions 121 and 122 in the opposite direction along the Z axis. Therefore, it is difficult to initialize the magnetic recording layer. The same applies even if the magnetic recording layer has a U shape in the XY plane.

  One object of the present invention is to provide a technique capable of easily realizing magnetization fixation (initialization) in a magnetic recording layer having perpendicular magnetic anisotropy.

  In a first aspect of the present invention, a magnetic recording device is provided. The magnetic recording device includes a magnetic recording layer that is a ferromagnetic layer having perpendicular magnetic anisotropy. The magnetic recording layer includes a magnetization reversal region, a first magnetization fixed region that is connected to the first boundary of the magnetization reversal region and the magnetization direction is fixed in the first direction, and a second magnetization boundary that is connected to the second boundary of the magnetization reversal region. A second magnetization fixed region whose direction is fixed in a second direction opposite to the first direction. Consider the sign of the slope of the tangent to the periphery of the magnetic recording layer in the plane on which the magnetic recording layer is formed. At this time, the majority of the above-mentioned sign relating to the first magnetization fixed region is opposite to the majority of the above-mentioned sign relating to the second magnetization fixed region.

  In a second aspect of the present invention, a magnetic recording device is provided. The magnetic recording device includes a magnetic recording layer that is a ferromagnetic layer having perpendicular magnetic anisotropy. The magnetic recording layer is connected to a magnetization reversal region, a first magnetization fixed region connected to a first boundary of the magnetization reversal region and having a magnetization direction fixed in the first direction, and a second boundary of the magnetization reversal region, And a second magnetization fixed region fixed in a second direction opposite to the first direction. In the plane on which the magnetic recording layer is formed, the first magnetization fixed region and the second magnetization fixed region have a rectangular shape. The direction in which the short side of the first magnetization fixed region extends is orthogonal to the direction in which the short side of the second magnetization fixed region extends.

  In a third aspect of the present invention, a magnetic recording device is provided. The magnetic recording device includes a magnetic recording layer that is a ferromagnetic layer having perpendicular magnetic anisotropy. The magnetic recording layer has a first magnetization fixed region and a second magnetization fixed region. Consider a case where an external magnetic field parallel to the surface on which the magnetic recording layer is formed is applied. At this time, the majority of the sign of the outer product of the magnetization of the first magnetization fixed region and the demagnetizing field generated at the end of the first magnetization fixed region is the magnetization of the second magnetization fixed region and the end of the second magnetization fixed region. It is the opposite of the majority of the sign of the outer product with the demagnetizing field generated.

  In a fourth aspect of the present invention, there is provided a magnetization pinning method in a magnetic recording layer which is a ferromagnetic layer having perpendicular magnetic anisotropy. The magnetic recording layer has a first magnetization fixed region and a second magnetization fixed region. The magnetization fixing method includes: (A) applying an external magnetic field parallel to the surface on which the magnetic recording layer is formed; and (B) stopping applying the external magnetic field. In the step (A), the majority of the sign of the outer product of the magnetization of the first magnetization fixed region and the demagnetizing field generated at the end of the first magnetization fixed region is the magnetization of the second magnetization fixed region and the second magnetization fixed region. Is the opposite of the majority of the sign of the sum of the outer products with the demagnetizing field generated at the end of.

  According to the present invention, a magnetic recording device including a magnetic recording layer having perpendicular magnetic anisotropy is provided. Accordingly, the write current is reduced and the power consumption is reduced as compared with the case of in-plane magnetic anisotropy. Further, in the magnetic recording layer having the perpendicular magnetic anisotropy, the magnetization can be fixed and the domain wall can be easily generated (initialized). As a result, the manufacturing cost is reduced.

  The above and other objects, advantages, and features will become apparent from the embodiments of the present invention described in conjunction with the following drawings.

FIG. 1 is a plan view showing the structure of the magnetic recording layer of the MRAM described in the related literature. FIG. 2 is a plan view showing the structure of the magnetic recording layer of the MRAM described in another related document. FIG. 3A is a plan view showing an example of the structure of a magnetic recording layer having perpendicular magnetic anisotropy. FIG. 3B shows a cross-sectional structure of the magnetic recording layer shown in FIG. 3A. FIG. 4A is a plan view showing the structure of the magnetic memory cell according to the exemplary embodiment of the present invention. FIG. 4B shows a cross-sectional structure of the magnetic memory cell shown in FIG. 4A. FIG. 5 is a schematic diagram for explaining the principle of data writing. FIG. 6 is a plan view showing an example of initialization of a magnetic layer having perpendicular magnetic anisotropy. FIG. 7 is a plan view showing another example of initialization of a magnetic layer having perpendicular magnetic anisotropy. FIG. 8 is a plan view showing initialization of the magnetic recording layer in the first embodiment. FIG. 9 is a plan view showing initialization of the magnetic recording layer in the first embodiment. FIG. 10A is a plan view showing an example of the structure of the magnetic recording layer in the second embodiment. FIG. 10B is a plan view showing another example of the structure of the magnetic recording layer in the second embodiment. FIG. 10C is a plan view showing still another example of the structure of the magnetic recording layer in the second embodiment. FIG. 10D is a plan view showing still another example of the structure of the magnetic recording layer in the second embodiment. FIG. 10E is a plan view showing still another example of the structure of the magnetic recording layer in the second embodiment. FIG. 11A is a plan view showing an example of the structure of the magnetic recording layer in the third embodiment. FIG. 11B is a plan view showing another example of the structure of the magnetic recording layer in the third embodiment. FIG. 11C is a plan view showing still another example of the structure of the magnetic recording layer in the third embodiment. FIG. 12 is an enlarged view showing an example of initialization around the boundary between the magnetization fixed region and the magnetization switching region. FIG. 13 is an enlarged view showing another example of initialization around the boundary between the magnetization fixed region and the magnetization switching region. FIG. 14A is a plan view showing an example of the structure of the magnetic recording layer in the fourth embodiment. FIG. 14B is a plan view showing another example of the structure of the magnetic recording layer in the fourth embodiment. FIG. 15 is a plan view showing the initialization of the magnetic recording layer in the fifth embodiment. FIG. 16 is a plan view showing still another example of initialization of a magnetic layer having perpendicular magnetic anisotropy. FIG. 17 is a plan view showing the initialization of the magnetic recording layer in the sixth embodiment. FIG. 18 is a plan view showing the initialization of the magnetic recording layer in the seventh embodiment. FIG. 19 is a plan view for explaining initialization for a generalized magnetization region. FIG. 20 is a block diagram showing an example of a circuit configuration of the MRAM according to the embodiment of the present invention. FIG. 21 is a plan view showing another application example of the present invention.

  A magnetic recording apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings. An example of the magnetic recording device is an MRAM including a plurality of magnetic memory cells arranged in an array. Each of the magnetic memory cells includes a magnetoresistive element exhibiting a magnetoresistive effect. The MRAM described in the embodiment of the present invention is a domain wall motion type MRAM using a magnetic recording layer having perpendicular magnetic anisotropy.

1. Basic Structure of Magnetic Memory Cell FIGS. 4A and 4B are a plan view and a cross-sectional view showing an example of the structure of the magnetic memory cell 1 (magnetoresistance element), respectively. The magnetic memory cell 1 includes a magnetic recording layer 10 that is a ferromagnetic layer, a tunnel barrier layer 20 that is a nonmagnetic layer, and a pinned layer (magnetization pinned layer) 30 that is a ferromagnetic layer. The magnetic recording layer 10 and the pinned layer 30 are connected to each other via the tunnel barrier layer 20. The magnetic recording layer 10, the tunnel barrier layer 20, and the pinned layer 30 are each formed in parallel to the XY plane. The magnetic recording layer 10, the tunnel barrier layer 20, and the pinned layer 30 are stacked in the Z-axis direction orthogonal to the XY plane.

  The tunnel barrier layer 20 is a thin insulating film, for example, an alumina oxide film (Al-Ox) or a magnesium oxide (MgO) film obtained by oxidizing an Al film. The tunnel barrier layer 20 is sandwiched between the magnetic recording layer 10 and the pinned layer 30, and the magnetic recording layer 10, the tunnel barrier layer 20, and the pinned layer 30 form a magnetic tunnel junction (MTJ).

  The magnetic recording layer 10 and the pinned layer 30 are ferromagnetic films made of iron (Fe), cobalt (Co), nickel (Ni), or an alloy containing at least one of these. In particular, in the present embodiment, the magnetic recording layer 10 and the pinned layer 30 are perpendicular magnetization films having “perpendicular magnetic anisotropy”. The direction of magnetization of the perpendicular magnetization film is generally orthogonal to the surface on which the film is formed, that is, parallel to the normal direction of the film. For example, in FIGS. 4A and 4B, the magnetizations of the magnetic recording layer 10 and the pinned layer 30 are generally in the + Z direction or the −Z direction.

  When the perpendicular magnetization film contains Pt or Pd, the perpendicular magnetic anisotropy is more stabilized and preferable. In addition, B, C, N, O, Al, Si, P, Ti, V, Cr, Mn, Cu, Zn, Zr, Nb, Mo, Tc, Ru, Rh, Ag, Hf, Ta, W, By adding Re, Os, Ir, Au, Sm, or the like, adjustment can be performed so that the perpendicular magnetization film exhibits desired magnetic characteristics. Therefore, the materials of the magnetic recording layer 10 and the pinned layer 30 include Co, Co—Pt, Co—Pd, Co—Cr, Co—Pt—Cr, Co—Cr—Ta, Co—Cr—B, and Co—Cr. -Pt-B, Co-Cr-Ta-B, Co-V, Co-Mo, Co-W, Co-Ti, Co-Ru, Co-Rh, Fe-Pt, Fe-Pd, Fe-Co-Pt , Fe—Co—Pd, Sm—Co and the like. Alternatively, a layer containing at least one material selected from Fe, Co, and Ni may be stacked with another layer. In this case, a laminated structure of Co / Pd, Co / Pt, Fe / Au, etc. is exemplified. A material having a large TMR effect, such as CoFe or CoFeB, may be used for a part of the magnetic recording layer 10 or the pinned layer 30, particularly a part in contact with the tunnel barrier layer 20.

  The magnetization direction of the pinned layer 30 is not changed by writing and reading operations. Therefore, the magnetic anisotropy of the pinned layer 30 is desirably larger than that of the magnetic recording layer 10. This can be realized by changing materials and compositions of the magnetic recording layer 10 and the pinned layer 30. A known antiferromagnetic layer for fixing the magnetization direction of the pinned layer 30 may be laminated on the surface of the pinned layer 30 opposite to the tunnel barrier layer 20. The pinned layer 30 may be a laminated film in which a ferromagnetic layer, a nonmagnetic layer, and a ferromagnetic layer are laminated in this order. At this time, Ru, Cu or the like is used as the material of the nonmagnetic layer. The magnetization directions of the two ferromagnetic layers are antiparallel to each other, and the leakage magnetic field from the pinned layer 30 can be suppressed by making the magnetizations of the two ferromagnetic layers equal.

  4A and 4B, the magnetic recording layer 10 according to the embodiment includes a first magnetization fixed region 11, a second magnetization fixed region 12, and a magnetization switching region 13 which are three different regions. ing. The magnetization switching region 13 extends along the X axis so as to connect between the first magnetization fixed region 11 and the second magnetization fixed region 12. The first magnetization fixed region 11 and the second magnetization fixed region 12 are formed on both sides of the magnetization switching region 13. More specifically, the first magnetization fixed region 11 and the magnetization switching region 13 are in contact with each other at the first boundary B1, and the second magnetization fixed region 12 and the magnetization switching region 13 are in contact with each other at the second boundary B2. ing. The first boundary B1 and the second boundary B2 of the magnetization switching region 13 coincide with opposite side surfaces that intersect with the X axis. The X axis is parallel to a line connecting the first boundary B1 and the second boundary B2 with the shortest distance. The Y axis is orthogonal to the X axis and the Z axis.

  The first magnetization fixed region 11, the second magnetization fixed region 12, and the magnetization switching region 13 are formed on the same plane (XY plane). Of these, the magnetization switching region 13 overlaps the pinned layer 30 as shown in FIG. 4B. In other words, the magnetization switching region 13 which is a part of the magnetic recording layer 10 is connected to the pinned layer 30 via the tunnel barrier layer 20 and bears a part of the MTJ.

  In FIG. 4A and FIG. 4B, an example of the direction of magnetization in each region is indicated by an arrow. In the magnetic recording layer 10, the magnetization directions of the first magnetization fixed region 11 and the second magnetization fixed region 12 are fixed. In particular, the magnetization of the first magnetization fixed region 11 and the magnetization of the second magnetization fixed region 12 are fixed in opposite directions (antiparallel). As described above, since the magnetic recording layer 10 has perpendicular magnetic anisotropy, the magnetizations of the first magnetization fixed region 11 and the second magnetization fixed region 12 are fixed in the opposite directions along the Z direction. In the example shown in FIGS. 4A and 4B, the magnetization of the first magnetization fixed region 11 is fixed in the −Z direction, and the magnetization of the second magnetization fixed region 12 is fixed in the + Z direction. Note that “magnetization is fixed” means that the magnetization direction does not change before and after the write operation. Even if the magnetization direction of a part of the magnetization fixed region changes during the write operation, it returns to the original state after the write operation is completed.

  On the other hand, the magnetization switching region 13 has reversible magnetization. That is, the magnetization direction of the magnetization switching region 13 is allowed to be the + Z direction or the −Z direction. In the example shown in FIGS. 4A and 4B, the magnetization direction of the magnetization switching region 13 is the −Z direction. In this case, the first magnetization fixed region 11 and the magnetization switching region 13 form one magnetic domain, and the second magnetization fixed region 12 forms another magnetic domain. Accordingly, a domain wall DW is formed at the second boundary B <b> 2 between the second magnetization fixed region 12 and the magnetization switching region 13. On the other hand, when the magnetization direction of the magnetization switching region 13 is the + Z direction, the second magnetization fixed region 12 and the magnetization switching region 13 form one magnetic domain, and the first magnetization fixed region 11 forms another magnetic domain. Accordingly, the domain wall DW is formed at the first boundary B1 between the first magnetization fixed region 11 and the magnetization switching region 13.

  Thus, in the magnetic recording layer 10, the domain wall DW is formed at the first boundary B1 or the second boundary B2. The reason why the first boundary B1 works as a pin potential with respect to the domain wall DW is that the width (Y-axis direction) of the first magnetization fixed region 11 near the first boundary B1 is larger than that of the magnetization switching region 13 ( (See FIG. 4A). Similarly, the second boundary B2 works as a pin potential with respect to the domain wall DW because the width (Y-axis direction) of the second magnetization fixed region 12 in the vicinity of the second boundary B2 is larger than that of the magnetization switching region 13. (See FIG. 4A). In order to form a pin potential, a constriction may be formed as shown in FIG. 3A.

  Here, it is assumed that the magnetization direction of the pinned layer 30 is fixed in the −Z direction. When the magnetization direction of the magnetization switching region 13 is in the −Z direction, that is, when the domain wall DW is formed at the second boundary B2, the magnetization of the pinned layer 30 and the magnetization switching region 13 is parallel. This parallel state is a state in which the MTJ resistance value is relatively small, and is associated with, for example, data “0”. On the other hand, when the magnetization direction of the magnetization switching region 13 is the + Z direction, that is, when the domain wall DW is formed at the first boundary B1, the magnetization of the pinned layer 30 and the magnetization switching region 13 is antiparallel. This antiparallel state is a state in which the resistance value of the MTJ is relatively large, and is associated with, for example, data “1”. As described above, the position of the domain wall DW in the magnetic recording layer 10 reflects the data recorded in the magnetic memory cell 1.

2. Data Writing / Data Reading Principle Next, a data writing operation and a data reading operation for the magnetic memory cell 1 will be described with reference to FIG. In FIG. 5, the first wiring 41 is electrically connected to the first magnetization fixed region 11 of the magnetic recording layer 10, and the second wiring 42 is electrically connected to the second magnetization fixed region 12. Further, the read wiring 50 is electrically connected to the pinned layer 30.

  Data writing is performed by passing a write current in the plane of the magnetic recording layer 10 and moving the domain wall DW between the first boundary B1 and the second boundary B2 (current-driven domain wall motion: Current-Driven Domain Wall Motion). ). Therefore, a predetermined potential difference is applied between the first wiring 41 and the second wiring 42.

  When data “1” is written, a write current flows from the first wiring 41 through the magnetic recording layer 10 to the second wiring 42. In this case, in the magnetic recording layer 10, electrons flow from the second magnetization fixed region 12 to the magnetization switching region 13 through the second boundary B2. That is, spin electrons in the + Z direction are injected into the magnetization switching region 13 from the second magnetization fixed region 12. As a result of the spin transfer by the spin electrons, the magnetization of the magnetization switching region 13 starts to be gradually reversed in the + Z direction from the vicinity of the second boundary B2. This means that the domain wall DW moves from the second boundary B2 toward the first boundary B1. When the write current continues to flow, the domain wall DW passes through the magnetization switching region 13 and reaches the first boundary B1. The domain wall DW stops at the first boundary B1 due to the pin potential.

  On the other hand, when writing data “0”, the write current flows from the second wiring 42 through the magnetic recording layer 10 into the first wiring 41. In this case, in the magnetic recording layer 10, electrons flow from the first magnetization fixed region 11 to the magnetization switching region 13 through the first boundary B1. That is, spin electrons in the −Z direction are injected into the magnetization switching region 13 from the first magnetization fixed region 11. As a result of the spin transfer by the spin electrons, the magnetization of the magnetization switching region 13 starts to be gradually reversed in the −Z direction from the vicinity of the first boundary B1. This means that the domain wall DW moves from the first boundary B1 toward the second boundary B2. When the write current continues to flow, the domain wall DW passes through the magnetization switching region 13 and reaches the second boundary B2. The domain wall DW stops at the second boundary B2 due to the pin potential.

  Thus, the 1st magnetization fixed area | region 11 and the 2nd magnetization fixed area | region 12 by which magnetization was fixed in the reverse direction play the role of the supply source of the electron which has a different spin. Then, the domain wall DW in the magnetic recording layer 10 moves between the first boundary B1 and the second boundary B2 by the write current flowing between the first magnetization fixed region 11 and the second magnetization fixed region 12. As a result, the magnetization direction of the magnetization switching region 13 is switched. That is, a domain wall motion type MRAM using current-driven domain wall motion is realized. Since the write current does not penetrate the tunnel barrier layer 20, the deterioration of the tunnel barrier layer 20 is suppressed. In addition, since the magnetic recording layer 10 has perpendicular magnetic anisotropy, the write current is reduced as compared with the case of in-plane magnetic anisotropy.

  The data read operation is as follows. At the time of data reading, a read current is supplied so as to flow between the pinned layer 30 and the magnetization switching region 13 through the tunnel barrier layer 20. For example, in FIG. 5, the read current is supplied from the second wiring 42 to the magnetic recording layer 10, passes through the MTJ (magnetization switching region 13, tunnel barrier layer 20, pinned layer 30) and flows to the read wiring 50. The magnitude of the MTJ resistance value is detected by comparing the read current or the read potential corresponding to the read current with a predetermined reference level. That is, the magnetization direction (+ Z direction or −Z direction) of the magnetization switching region 13 is sensed, and the data (“0” or “1”) recorded in the magnetic memory cell 1 is sensed.

  As described above, the magnetic memory cell 1 can store data “0” or “1”. Further, the data can be rewritten by passing a write current in the plane of the magnetic recording layer 10. In order to realize such a magnetic memory cell 1, it is necessary to fix the magnetization directions of the magnetization fixed regions 11 and 12 and generate the domain wall DW in the magnetic recording layer 10. That is, it is necessary to initialize the magnetization of the magnetic recording layer 10. As will be described in the next section, the magnetic recording layer 10 according to the present embodiment has a shape suitable for initialization.

3. Magnetic Recording Layer In the present invention, the magnetic recording layer 10 has perpendicular magnetic anisotropy and has a specific planar shape. Hereinafter, the magnetic recording layer 10 and its initialization method (magnetization fixing method) will be described by giving various embodiments.

3-1. First Embodiment In the first embodiment, the magnetic recording layer 10 has a planar shape as shown in FIG. 4A. That is, the first magnetization fixed region 11 and the second magnetization fixed region 12 have a parallelogram shape on the XY plane. Further, the shape of the first magnetization fixed region 11 and the shape of the second magnetization fixed region 12 are mirror-symmetric with respect to the Y axis. That is, the inclination of the parallelogram side of the first magnetization fixed region 11 is opposite to the inclination of the side of the parallelogram of the second magnetization fixed region 12.

  In order to explain the action and effect of such a planar shape, first, initialization of the magnetized region 60 having a rectangular shape will be described with reference to FIG. In FIG. 6, the magnetized region 60 has perpendicular magnetic anisotropy and has a rectangular shape in the XY plane. The sides of the magnetized region 60 include an upper side 62a and a lower side 62b that are orthogonal to the Y axis. That is, the upper side 62a and the lower side 62b are parallel to the X axis.

  In the initialization of the magnetization region 60, first, a strong external magnetic field (in-plane magnetic field) parallel to the XY plane is applied. Specifically, an external magnetic field in the + Y direction is applied. If the magnitude of the external magnetic field is equal to or greater than that of the anisotropic magnetic field, the magnetization 61 of the magnetization region 60 faces the + Y direction. At this time, as shown in the state (A), positive and negative magnetic poles 63a and 63b are generated near the upper side 62a and the lower side 62b by the magnetization 61, respectively. As a result, demagnetizing fields 64a and 64b are applied to the ends of the magnetized region 60, particularly in the vicinity of the upper side 62a and the lower side 62b. At this time, it should be noted that the directions of the demagnetizing fields 64 a and 64 b are generally opposite to the direction of the magnetization 61, but have an X component near the corner of the magnetization region 60.

  Next, the application of the external magnetic field in the + Y direction is stopped. In response to this, the magnetization 61 in the magnetization region 60 starts to rotate. Ultimately, the magnetization 61 faces the + Z direction or the −Z direction due to the perpendicular magnetic anisotropy. The motion of the magnetization 61 at this time is described by the Landau-Lifschitz-Gilbert (LLG) equation expressed by the following equation (1).

  Here, M is a magnetization vector, H is an effective magnetic field, γ is a gyromagnetic constant, α is a damping coefficient, and Ms is a saturation magnetization. The first term on the right side is a torque term, and the second term is an attenuation term. However, since α << 1, the initial behavior of the magnetization 61 is determined by the torque term (first term). The effective magnetic field H includes an external magnetic field, a demagnetizing field, an anisotropic magnetic field, an exchange magnetic field, and the like. After the application of the external magnetic field is stopped, the main component of the effective magnetic field H that drives the magnetization 61 is a demagnetizing field.

  As shown in the state (A), most of the demagnetizing fields 64a and 64b are antiparallel to the magnetization 61 in the + Y direction and do not contribute to the torque term. However, since the demagnetizing fields 64a and 64b have an X component near the corner of the magnetized region 60, the X component contributes to the torque term. That is, as shown in the state (B), the torque 65 due to the torque term is generated near the corner portion of the magnetization region 60. The direction of the torque 65 includes both the + Z direction and the −Z direction. Due to the torque 65 and the perpendicular magnetic anisotropy, the magnetization 61 at the corner portion is directed in the direction of the torque 65, that is, the + Z direction or the −Z direction.

  As time elapses, the perpendicular magnetization 61 near the corner expands the area. Ultimately, a state in which the magnetization 61 in the + Z direction and the magnetization 61 in the −Z direction are mixed is obtained (state (C)). That is, a plurality of perpendicular magnetic domains are formed in the magnetization region 60, and the domain wall 66 is formed in different magnetic sections. However, the state (C) occurs when the expansion of the vertical magnetic domains from the four corners is substantially constant. When there is a difference in the spread of magnetic domains due to defects, leakage magnetic fields, etc., the upper left and lower right magnetic domains, or the lower left and upper right magnetic domains are coupled together, and the remaining magnetic domains are expelled. As a result, a single perpendicular magnetic domain may be formed as shown in the state (D) or the state (E).

  It is difficult to control how the magnetic domains expand in the magnetization region 60. That is, it is probabilistic which state (C), state (D), or state (E) is obtained as a result of the initialization of the magnetization region 60. It is not preferable that the magnetization state is determined stochastically in the initialization process in which the magnetization region 60 needs to be set to a desired state.

  Next, the case of the parallelogram shape will be described with reference to FIG. In FIG. 7, the magnetized region 70 has perpendicular magnetic anisotropy and has a parallelogram shape in the XY plane. The sides of the magnetized region 70 include an upper side 72a and a lower side 72b that intersect both the X axis and the Y axis. That is, the upper side 72a and the lower side 72b are not parallel to the X axis, and the inclinations with respect to the X axis are both positive.

  As in the case of FIG. 6, an external magnetic field (in-plane magnetic field) in the + Y direction is applied, whereby the magnetization 71 of the magnetization region 70 is directed in the + Y direction. At this time, as shown in the state (A), positive and negative magnetic poles 73a and 73b are generated near the upper side 72a and the lower side 72b by the magnetization 71, respectively. As a result, demagnetizing fields 74a and 74b are applied so as to be substantially orthogonal to the upper side 72a and the lower side 72b. At this time, since the upper side 72a and the lower side 72b are inclined from the X axis, most of the demagnetizing fields 74a and 74b have a + X component.

  Next, the application of the external magnetic field in the + Y direction is stopped. In response to this, the magnetization 71 in the magnetization region 70 starts to rotate. As described above, most of the demagnetizing fields 74a and 74b have a + X component and contribute to the torque term. As a result, as shown in the state (B), a torque 75 due to a torque term is generated near the end of the magnetization region 70. Since most of the demagnetizing fields 74a and 74b have a + X component, the direction of most of the torque 75 is the + Z direction (see Expression (1)).

  Due to the torque 75 and the perpendicular magnetic anisotropy, the magnetization 71 in the vicinity of the upper side 72a and the lower side 72b comes to the + Z direction. As time elapses, the perpendicular magnetization 71 in the + Z direction expands the region. Eventually, as shown in the state (C), the magnetization 71 is directed in the + Z direction over the entire magnetization region 70. That is, a single magnetic domain in the + Z direction is obtained.

  As described above, in the case of the example shown in FIG. 7, the direction of the magnetization 71 of the magnetization region 70 as a result of the initialization is determined in one direction (+ Z direction). This is because the majority of the torque 75 is biased in one direction (+ Z direction). In other words, referring to the torque term (first term) in the above formula (1), it is as follows. When an external magnetic field (in-plane magnetic field) in the + Y direction is applied to the magnetization region 70, the sign of the outer product of the magnetization 71 (M) of the magnetization region 70 and the demagnetization fields 74a and 74b (H) generated at the ends Majority is negatively biased. As a result, the majority of the torque 75 (−M × H) is biased in the + Z direction, and after the application of the external magnetic field is stopped, the magnetization 71 is directed in the + Z direction over the entire magnetization region 70.

  Even if a torque in the opposite direction (−Z direction) is generated in a part of the magnetized region 70, there is no problem as long as it is a minority. In the magnetization process, the majority torque overcomes the minority torque, so that the magnetization 71 is directed in the same direction throughout the magnetization region 70. Therefore, it is not always necessary to generate torque in the same direction over the entire region of the magnetized region 70. What is important is that the majority of the torque is biased in one direction. Such a concept of “majority of torque” or “majority of sign of outer product of magnetization and demagnetizing field” is often used in the following description.

  In the example shown in FIG. 6, the torque 65 in the + Z direction and the torque 65 in the −Z direction are generated by substantially the same amount in the magnetization region 60 (see state (B)). In other words, there was no torque majority. Therefore, a multi-domain structure as shown in the state (C) is generated. Alternatively, factors such as defects and leakage magnetic fields may affect the magnetic domain structure (see state (D) and state (E)). The reason why the magnetization state as a result of the initialization depends on the probability is that there is no torque majority. In other words, it is considered that a desired magnetization state can be obtained by intentionally generating a majority of torque.

  There is a difference in the planar shape of the magnetization region between the example shown in FIG. 6 and the example shown in FIG. It can be said that this difference in the planar shape led to the presence or absence of torque majority, and consequently the difference in the result of initialization. Therefore, it is possible to perform initialization without depending on the probability by designing the planar shape of the magnetization region so that the majority of torque is generated. That is, initialization (magnetization fixation) can be performed easily and stably.

  In the example shown in FIG. 6, the sides that intersect the direction of the applied external magnetic field (+ Y direction) are the upper side 62 a and the lower side 62 b. The upper side 62a and the lower side 62b are parallel to the X axis. On the other hand, in the example shown in FIG. 7, the sides that intersect the direction of the applied external magnetic field (+ Y direction) are the upper side 72a and the lower side 72b. Neither the upper side 72a nor the lower side 72b is parallel to the X axis, and the inclinations with respect to the X axis are both positive. Accordingly, when the demagnetizing fields 74a and 74b are generated so as to be substantially orthogonal to the upper side 72a and the lower side 72b, most of the demagnetizing fields 74a and 74b have a + X component. As a result, torque majority is generated.

  Thus, when the in-plane magnetic field in the Y direction is applied, the inclination of the tangent of each side with respect to the X axis is important. The majority of the sign (positive or negative) of inclination with respect to the X axis is directly connected to the majority of torque. In FIG. 7, the parallelogram shape also has a side parallel to the Y axis. The inclination of the side with respect to the X axis is infinite. Such an infinite slope is not considered here. This is because no demagnetizing field is generated near the side parallel to the Y axis. When an in-plane magnetic field in the Y direction is applied, only a finite tilt with respect to the X axis need be considered.

  Consider a sign of a finite inclination with respect to the X axis of the periphery (each side) of the magnetized region. In the example shown in FIG. 7, the majority of the signs related to the periphery of the magnetized region 70 is “positive”. In this case, as a result of the initialization of the magnetization region 70, the magnetization 71 faces the + Z direction. On the other hand, when the majority of the sign is “negative”, the magnetization 71 faces the −Z direction. As described above, the initialization result depends on the “majority of the sign of the slope”. In other words, the initialization can be controlled by designing the planar shape of the magnetization region so as to obtain a desired majority with respect to the sign. Such a concept of “majority of the sign of inclination” is also often used in the following description.

  FIG. 8 is a plan view showing initialization of the magnetic recording layer 10 according to the first embodiment. In the present embodiment, the first magnetization fixed region 11 and the second magnetization fixed region 12 have a parallelogram shape. The periphery of the first magnetization fixed region 11 includes an upper side 81a and a lower side 81b that intersect both the X axis and the Y axis. The inclinations of the upper side 81a and the lower side 81b with respect to the X-axis are equal and both are “negative”. On the other hand, the periphery of the second magnetization fixed region 12 includes an upper side 82a and a lower side 82b that intersect both the X axis and the Y axis. The inclinations of the upper side 82a and the lower side 82b with respect to the X-axis are equal and both are “positive”. That is, the signs of the slopes of the upper side 81a and the lower side 81b are opposite to the signs of the slopes of the upper side 82a and the lower side 82b. Further, the shape of the first magnetization fixed region 11 and the shape of the second magnetization fixed region 12 are mirror-symmetric with respect to the Y axis.

  The method for initializing the magnetic recording layer 10 is the same as that shown in FIG. That is, first, an external magnetic field (in-plane magnetic field) is applied in the + Y direction. Thereby, the magnetization 80-1 of the first magnetization fixed region 11, the magnetization 80-2 of the second magnetization fixed region 12, and the magnetization 80-3 of the magnetization switching region 13 are directed in the + Y direction. At this time, a demagnetizing field is applied to the end of the magnetic recording layer 10 as shown in the state (A).

  Regarding the periphery of the first magnetization fixed region 11, the majority of the sign of the inclination is “negative”. Therefore, most of the demagnetizing field 84-1 generated at the end of the first magnetization fixed region 11 has a -X component. As a result, as shown in the state (B), the majority in the direction of the torque 85-1 generated in the first magnetization fixed region 11 is the -Z direction. On the other hand, with respect to the periphery of the second magnetization fixed region 12, the majority of the sign of the inclination is “positive”. Therefore, most of the demagnetizing field 84-2 generated at the end of the second magnetization fixed region 12 has a + X component. As a result, as shown in the state (B), the majority in the direction of the torque 85-2 generated in the second magnetization fixed region 12 is the + Z direction.

  When the application of the external magnetic field in the + Y direction is stopped, the magnetization of the magnetic recording layer 10 is directed in the + Z direction or the −Z direction due to torque and perpendicular magnetic anisotropy. Specifically, as shown in the state (C), the magnetization 80-1 of the first magnetization fixed region 11 is directed in the -Z direction by the torque 85-1 in the -Z direction. On the other hand, the magnetization 80-2 of the second magnetization fixed region 12 is directed in the + Z direction by the torque 85-2 in the + Z direction. As described above, the magnetization direction of the magnetization fixed regions 11 and 12 can be easily initialized in the reverse direction only by applying and stopping the external magnetic field in the + Y direction.

  In the state (C) in FIG. 8, the magnetization 80-3 of the magnetization switching region 13 is in the −Z direction like the first magnetization fixed region 11, and the domain wall DW is the same as the second magnetization fixed region 12. It is generated at the second boundary B2 between the magnetization switching regions 13. However, since the planar shape of the magnetization switching region 13 is a rectangle, the magnetization state of the magnetization switching region 13 may be in a different state as in the example shown in FIG.

  FIG. 9 shows examples of other magnetization states that the magnetization switching region 13 can take. In the state (C1), the direction of the magnetization 80-3 of the magnetization switching region 13 is the + Z direction, and the domain wall DW is generated at the first boundary B1 between the first magnetization fixed region 11 and the magnetization switching region 13. . In the state (C2), the magnetization 80-3 on the first magnetization fixed region 11 side faces the −Z direction, and the magnetization 80-3 on the second magnetization fixed region 12 side faces the + Z direction. Therefore, the domain wall DW is generated near the center of the magnetization switching region 13. In the state (C3), the magnetization 80-3 on the first magnetization fixed region 11 side faces the + Z direction, and the magnetization 80-3 on the second magnetization fixed region 12 side faces the -Z direction. Accordingly, three domain walls DW are generated at different positions of the magnetic recording apparatus 10.

  Thus, the processing described with reference to FIG. 8 alone may not be sufficient for initializing the position and number of domain walls. In order to determine the position of the domain wall, the following processing may be performed. That is, after the application of the external magnetic field in the + Y direction (first external magnetic field) is finished, an external magnetic field (second external magnetic field) along the Z direction orthogonal to the XY plane is applied. For example, by applying a second external magnetic field in the −Z direction, the magnetization 80-3 of the entire magnetization switching region 13 faces the −Z direction, and the state (C) shown in FIG. 8 is obtained. At this time, the magnitude of the second external magnetic field is set such that the magnetization 80-2 (+ Z direction) of the second magnetization fixed region 12 is not reversed. The application of the second external magnetic field may be performed simultaneously with the application of the first external magnetic field.

  As described above, the magnetic recording layer 10 according to the present embodiment has a specific planar shape suitable for initialization. Specifically, in the XY plane, when the sign of the tangential slope with respect to the periphery of the magnetic recording layer 10 is considered, the majority of the sign related to the first magnetization fixed region 11 is the opposite of the majority of the sign related to the second magnetization fixed region 12. It is. By simply applying an external magnetic field in the XY plane to such a magnetic recording layer 10, the magnetization directions of the magnetization fixed regions 11 and 12 can be initialized in the reverse direction along the Z direction. It can be said that the magnetization directions of the magnetization fixed regions 11 and 12 as a result of initialization do not depend on the probability and are stable. That is, according to the present embodiment, it is possible to easily and stably initialize the magnetic recording layer 10 having perpendicular magnetic anisotropy. As a result, the manufacturing cost is reduced and the reliability is improved.

3-2. Second Embodiment The planar shapes of the first magnetization fixed region 11 and the second magnetization fixed region 12 are not limited to those shown in the first embodiment. Essentially, the majority of the sign of the inclination with respect to the periphery of the first magnetization fixed region 11 may be opposite to the majority of the sign of the inclination with respect to the periphery of the second magnetization fixed region 12. In the second embodiment, various examples of the planar shape of the magnetization fixed regions 11 and 12 are shown. In addition, the same reference number is attached | subjected to the same structure as the structure in 1st Embodiment, and the overlapping description is abbreviate | omitted suitably.

  In FIG. 10A, the first magnetization fixed region 11 and the second magnetization fixed region 12 have different sizes. That is, the shape of the first magnetization fixed region 11 and the shape of the second magnetization fixed region 12 are not mirror-symmetric with respect to the Y axis. However, the slopes of the upper side 81a and the lower side 81b of the first magnetization fixed region 11 are both “negative”, and the slopes of the upper side 82a and the lower side 82b of the second magnetization fixed region 12 are both “positive”. Therefore, the same effect as the first embodiment can be obtained.

  In FIG. 10B, the planar shapes of the first magnetization fixed region 11 and the second magnetization fixed region 12 are trapezoids. That is, the slopes of the upper side 81a and the lower side 81b of the first magnetization fixed region 11 and the upper side 82a and the lower side 82b of the second magnetization fixed region 12 are zero. However, the first magnetization fixed region 11 has a left side 81c that intersects the X axis and faces the first boundary B1. The inclination of the left side 81c with respect to the X axis is “positive”. That is, the majority of the sign of the inclination with respect to the periphery of the first magnetization fixed region 11 is “positive”. On the other hand, the second magnetization fixed region 12 has a right side 82c that intersects the X axis and faces the second boundary B2. The inclination of the right side 82c with respect to the X axis is “negative”. That is, the majority of the sign of the inclination with respect to the periphery of the second magnetization fixed region 12 is “negative”. Therefore, the same effect as the first embodiment can be obtained.

  In FIG. 10C, the first magnetization fixed region 11 has an upper side 81a, a lower side 81b, a left side 81c, and a right side 81d. The inclinations of all the sides 81a to 81d are “positive”, and the same torque in the + Z direction is obtained in the vicinity thereof. Similarly, the second magnetization fixed region 12 has an upper side 82a, a lower side 82b, a right side 82c, and a left side 82d. The inclinations of all the sides 82a to 82d are “negative”, and the same torque in the −Z direction is obtained in the vicinity thereof. Therefore, the same effect as the first embodiment can be obtained. In particular, since torque is generated in the vicinity of all sides, the success probability of initialization is extremely high.

  In FIG. 10D, the periphery of the 1st magnetization fixed area | region 11 and the 2nd magnetization fixed area | region 12 contains the curve. Even in this case, the inclination of the tangent to the periphery can be defined. The shape of the first magnetization fixed region 11 and the shape of the second magnetization fixed region 12 are mirror-symmetric with respect to the Y axis. The majority of the sign of the inclination with respect to the periphery of the first magnetization fixed region 11 is “positive”. On the other hand, the majority of the sign of the inclination with respect to the periphery of the second magnetization fixed region 12 is “negative”. Therefore, the same effect as the first embodiment can be obtained.

  In FIG. 10E, the periphery of the first magnetization fixed region 11 is a parallelogram, and the periphery of the second magnetization fixed region 12 includes a curve. The majority of the sign of the inclination with respect to the periphery of the first magnetization fixed region 11 is “positive”. On the other hand, the majority of the sign of the inclination with respect to the periphery of the second magnetization fixed region 12 is “negative”. Therefore, the same effect as the first embodiment can be obtained.

3-3. Third Embodiment In the first embodiment, in addition to the application of the first external magnetic field in the in-plane direction, it may be necessary to apply the second external magnetic field along the Z direction. In order to omit the process of applying the second external magnetic field, torque majority may be generated also in the magnetization switching region 13. In the third embodiment, the planar shape of the magnetization switching region 13 is improved. The same reference numerals are given to the same components as those in the above-described embodiments, and overlapping descriptions are omitted as appropriate.

  FIG. 11A shows an example of a planar shape of the magnetic recording layer 10 according to the third exemplary embodiment. In FIG. 11A, the planar shape of the magnetization switching region 13 is different from that shown in FIG. Specifically, the magnetization switching region 13 has a parallelogram shape similar to that of the first magnetization fixed region 11. That is, the periphery of the magnetization switching region 13 has an upper side 83a and a lower side 83b that intersect both the X axis and the Y axis. The inclinations of the upper side 83a and the lower side 83b with respect to the X-axis are equal and both are “negative”. In this case as well, the X axis is parallel to a line connecting the first boundary B1 and the second boundary B2 with the shortest distance.

  The magnetic recording layer 10 is also initialized by a method similar to the method shown in FIG. Since the majority of the sign of the inclination with respect to the magnetization switching region 13 is “negative”, a torque similar to that in the first magnetization fixed region 11 is generated in the magnetization switching region 13. As a result, the magnetization 80-3 of the magnetization switching region 13 is oriented in the -Z direction, and the domain wall DW is generated at the second boundary B2, that is, a desired position. Therefore, the application process of the second external magnetic field along the Z direction can be omitted.

  The planar shape of the magnetization switching region 13 is not limited to that shown in FIG. 11A. As in the case of the magnetization fixed regions 11 and 12, the planar shape of the magnetization switching region 13 may be designed so as to generate torque majority. For example, the planar shape of the magnetization switching region 13 may be a trapezoid. In that case, only one of the upper side 83a and the lower side 83b of the magnetization switching region 13 intersects both the X axis and the Y axis, and the other is parallel to the X axis. The same effect can be obtained with such a planar shape.

  In FIG. 11B, the lower side 83b of the magnetization switching region 13 is bent. That is, the width of the magnetization switching region 13 along the Y axis gradually increases from the boundary toward the center. The domain wall DW has a property of being more stabilized at a position where the cross-sectional area is smaller. Therefore, in the case of the planar shape shown in FIG. 11B, the domain wall DW is likely to be generated at the first boundary B1 or the second boundary B2. As a result, the state (C2) and state (C3) shown in FIG. 9, that is, the state where the domain wall DW is generated near the center of the magnetization switching region 13 is prevented. Since the domain wall DW only needs to be generated at either the first boundary B1 or the second boundary B2, the effect can be obtained even in the planar shape shown in FIG. 11B.

  FIG. 11C shows a combination of the shape of FIG. 11A and the shape of FIG. 11B. In this case, the success probability of initialization of the magnetization switching region 13 is further improved. The upper side 83a of the magnetization switching region 13 may be bent, or both the upper side 83a and the lower side 83b may be bent. The width along the Y axis of the magnetization switching region 13 only needs to be wider at the center than at the boundary. It is also possible to combine the second embodiment and the third embodiment.

3-4. Fourth Embodiment FIG. 12 shows the state (A) and the state (B) shown in FIG. 8 in more detail. Specifically, FIG. 12 shows in detail the state of initialization around the boundary between the first magnetization fixed region 11 and the magnetization switching region 13.

  When the first external magnetic field in the + Y direction is applied, a demagnetizing field 84-1 is generated in the vicinity of the upper side 81a and the lower side 81b of the first magnetization fixed region 11 as shown in the state (A). The demagnetizing field 84-1 has a -X component. At the same time, a demagnetizing field is also generated in the vicinity of the upper side 83a and the lower side 83b of the magnetization switching region 13. At this time, the demagnetizing field 86 a caused by the positive magnetic pole in the vicinity of the upper side 83 a extends to the inside of the first magnetization fixed region 11. Further, the demagnetizing field 86 b caused by the negative magnetic pole in the vicinity of the lower side 83 b also spreads inside the first magnetization fixed region 11.

  Inside the first magnetization fixed region 11, the demagnetizing field 86a has a -X component like the demagnetizing field 84-1. Therefore, as shown in the state (B), the direction of the torque 87a generated by the demagnetizing field 86a and the magnetization 80-1 is the −Z direction as is the torque 85-1. However, the demagnetizing field 86b has a + X component opposite to the demagnetizing field 84-1. Accordingly, as shown in the state (B), the direction of the torque 87b generated by the demagnetizing field 86b and the magnetization 80-1 is the + Z direction opposite to the torque 85-1. The torque 87b in the + Z direction works to prevent initialization of the first magnetization fixed region 11.

  As described above, a reverse torque may be generated in a part of the first magnetization fixed region 11 due to the influence of the magnetic pole of the magnetization switching region 13. The same applies to the second magnetization fixed region 12. If the influence of the reverse torque is limited in the overall torque, the final magnetization direction is the desired direction. However, when the influence of the reverse torque is relatively large, a reverse magnetic domain may remain. In the fourth embodiment, this point is improved.

  FIG. 13 is a diagram corresponding to FIG. 12 and shows a state (A) and a state (B) in the fourth embodiment. The same components as those already described are denoted by the same reference numerals, and redundant description will be omitted as appropriate.

  In FIG. 13, the lower side 83 b of the magnetization switching region 13 is connected to the lower side 81 b of the first magnetization fixed region 11. That is, the lower side 83b and the lower side 81b are not separated from each other, and the peripheral edge of the magnetic recording layer 10 is smoothly formed from the lower side 83b to the lower side 81b. In this case, when the first external magnetic field in the + Y direction is applied, the negative magnetic pole is smoothly distributed from the lower side 83b to the lower side 81b. As a result, the demagnetizing field 86b caused by the negative magnetic pole in the vicinity of the lower side 83b is difficult to face in the + X direction. Therefore, it becomes difficult to generate the reverse torque 87b, and the initialization of the first magnetization fixed region 11 can be more stably performed.

  Depending on the magnetization fixing direction of the first magnetization fixed region 11, the upper side 83 a of the magnetization switching region 13 may be connected to the upper side 81 a of the first magnetization fixed region 11. At least one side of the magnetization switching region 13 excluding the first boundary B1 and the second boundary B2 is connected to the upper side 81a or the lower side 81b of the first magnetization fixed region 11. The same applies to the second magnetization fixed region 12.

  14A and 14B show examples of the planar shape of the magnetic recording layer 10 according to the fourth embodiment. 14A, the lower side 83b of the magnetization switching region 13 is connected to the lower side 81b of the first magnetization fixed region 11 and the lower side 82b of the second magnetization fixed region 12. In FIG. 14B, the upper side 83a of the magnetization switching region 13 is further connected to the upper side 81a of the first magnetization fixed region 11 and the upper side 82a of the second magnetization fixed region 12. Such a structure makes it possible to stably initialize the magnetization fixed regions 11 and 12. Note that the fourth embodiment can be combined with any of the above-described embodiments.

3-5. Fifth Embodiment The direction of the first external magnetic field applied in the initialization of the magnetic recording layer 10 is not limited to the + Y direction. The first external magnetic field only needs to have an XY component as a main component. The direction of the main component is not limited to the + Y direction, and may be the −Y direction, the + X direction, or the −X direction. FIG. 15 is a plan view for explaining initialization in the fifth embodiment, and shows a case where a first external magnetic field in the + X direction is applied. The same components as those in the first embodiment are denoted by the same reference numerals, and redundant descriptions are omitted as appropriate.

  In FIG. 15, the relationship between the planar shapes of the first magnetization fixed region 11 and the second magnetization fixed region 12 is the same as that of the above-described embodiment. That is, the majority of the sign of the inclination with respect to the periphery of the first magnetization fixed region 11 is “negative”. On the other hand, the majority of the sign of the inclination with respect to the periphery of the second magnetization fixed region 12 is “positive”.

  In initialization, first, a first external magnetic field (in-plane magnetic field) is applied in the + X direction. Thereby, the magnetization 80-1 of the first magnetization fixed region 11, the magnetization 80-2 of the second magnetization fixed region 12, and the magnetization 80-3 of the magnetization switching region 13 are directed in the + X direction. At this time, a demagnetizing field is applied to the end of the magnetic recording layer 10 as shown in the state (A). Most of the demagnetizing field 84-1 generated at the end of the first magnetization fixed region 11 has a -Y component. On the other hand, most of the demagnetizing field 84-2 generated at the end of the second magnetization fixed region 12 has a + Y component.

  As a result, as shown in the state (B), the majority in the direction of the torque 85-1 generated in the first magnetization fixed region 11 is the + Z direction. On the other hand, the majority in the direction of the torque 85-2 generated in the second magnetization fixed region 12 is the -Z direction. When the application of the first external magnetic field in the + X direction is stopped, the magnetization of the magnetic recording layer 10 is directed in the + Z direction or the −Z direction due to torque and perpendicular magnetic anisotropy. Specifically, as shown in the state (C), the magnetization 80-1 of the first magnetization fixed region 11 is directed in the + Z direction by the torque 85-1 in the + Z direction. On the other hand, the magnetization 80-2 of the second magnetization fixed region 12 is directed in the -Z direction by the torque 85-2 in the -Z direction. As described above, the magnetization directions of the magnetization fixed regions 11 and 12 can be easily initialized in the reverse direction only by applying and stopping the external magnetic field in the + X direction.

  The planar shape of the magnetic recording layer 10 is not limited to that shown in FIG. As described in the second embodiment, various patterns are conceivable as the planar shape of the magnetization fixed regions 11 and 12. In addition, the magnetization switching region 13 shown in the third embodiment may be applied to this embodiment. In addition, the device described in the fourth embodiment may be applied to the present embodiment.

3-6. Sixth Embodiment FIG. 16 is a diagram corresponding to FIG. 6 described above, and shows another example of initialization of a magnetized region 60 having a rectangular shape. The magnetized region 60 has perpendicular magnetic anisotropy. The rectangular magnetized region 60 has short sides 62a and 62b parallel to the X axis and long sides 62c and 62d parallel to the Y axis. The long sides 62c and 62d are longer than the short sides 62a and 62b.

  In FIG. 16, the direction of the external magnetic field (in-plane magnetic field) applied in the XY plane is not the + Y direction. The direction of the applied external magnetic field is a direction that intersects both the X axis and the Y axis in the XY plane, and a direction that intersects all of the short sides 62a and 62b and the long sides 62c and 62d. Such a direction is hereinafter referred to as an “oblique direction”. When an oblique external magnetic field is applied, the magnetization 61 of the magnetization region 60 is directed obliquely. At this time, as shown in the state (A), demagnetizing fields 64a and 64b are applied in the vicinity of the short sides 62a and 62b, respectively. Further, demagnetizing fields 64c and 64d are applied in the vicinity of the long sides 62c and 62d, respectively.

  The directions of the demagnetizing fields 64a and 64b are approximately the -Y direction. Therefore, the directions of the torques 65a and 65b generated by the demagnetizing fields 64a and 64b in the -Y direction and the magnetization 61 in the oblique direction are the + Z direction. That is, as shown in the state (B), torque in the + Z direction is generated in the vicinity of the short sides 62a and 62b. On the other hand, the directions of the demagnetizing fields 64c and 64d are approximately the -X direction. Therefore, the directions of the torques 65c and 65d generated by the demagnetizing fields 64c and 64d in the -X direction and the magnetization 61 in the oblique direction are the -Z direction. That is, as shown in the state (B), torque in the −Z direction is generated in the vicinity of the long sides 62c and 62d.

  As described above, torques in opposite directions are generated in the vicinity of the short sides 62a and 62b and in the vicinity of the long sides 62c and 62d. Since the long side is longer than the short side, the majority of the torque related to the magnetization region 60 is in the −Z direction. Therefore, when the application of the external magnetic field is stopped, the torque in the + Z direction is driven out, and the magnetization 61 of the magnetization region 60 is entirely directed in the −Z direction (state (C)).

  As described above, even if the magnetization region 60 has a rectangular shape, the initialization of the magnetization region 60 can be controlled by setting the direction of the in-plane magnetic field to the “oblique direction”. In the sixth embodiment, this technique is applied.

  FIG. 17 is a plan view showing an example of initialization of the magnetic recording layer 10 in the sixth embodiment. The same reference numerals are given to the same components as those in the above-described embodiments, and overlapping descriptions are omitted as appropriate. According to the present embodiment, the first magnetization fixed region 11, the second magnetization fixed region 12, and the magnetization switching region 13 have a rectangular shape on the XY plane. The first magnetization fixed region 11 has short sides 91a and 91b parallel to the X axis and long sides 91c and 91d parallel to the Y axis. The second magnetization fixed region 12 has long sides 92a and 92b parallel to the X axis and short sides 92c and 92d parallel to the Y axis. That is, the X direction (Y direction) in which the short side (long side) of the first magnetization fixed region 11 extends is orthogonal to the Y direction (X direction) in which the short side (long side) of the second magnetization fixed region 12 extends. Yes. The magnetization switching region 13 has long sides 93a and 93b parallel to the X axis and short sides 93c and 93d parallel to the Y axis.

  The method for initializing the magnetic recording layer 10 is the same as in the case of FIG. That is, first, an external magnetic field is applied in an oblique direction intersecting with both the X axis and the Y axis. As a result, the magnetization 90-1 of the first magnetization fixed region 11, the magnetization 90-2 of the second magnetization fixed region 12, and the magnetization 90-3 of the magnetization switching region 13 are directed obliquely. At this time, a demagnetizing field is generated at the end of the magnetic recording layer 10 as shown in the state (A). Torque is generated at the end of the magnetic recording layer 10 by the demagnetizing field and the oblique magnetization (90-1, 90-2, 90-3).

  As shown in the state (B), the majority of the torque related to the first magnetization fixed region 11 is in the −Z direction. On the other hand, the majority of torque related to the second magnetization fixed region 12 and the magnetization switching region 13 is the + Z direction. Therefore, when the application of the external magnetic field is stopped, the magnetization 90-1 of the first magnetization fixed region 11 faces the -Z direction, while the magnetization 90-2 of the second magnetization fixed region 12 faces the + Z direction (state) (C)). As described above, the magnetization directions of the magnetization fixed regions 11 and 12 can be easily initialized in the reverse direction only by applying and stopping the external magnetic field in the oblique direction. Further, the magnetization 90-3 of the magnetization switching region 13 faces the + Z direction, and a domain wall DW is generated at the first boundary B1.

  The sixth embodiment is based on the same concept as the above-described embodiments. That is, the majority of the torque direction in the first magnetization fixed region 11 is opposite to the majority of the torque direction in the second magnetization fixed region 12. Further, when considering the sign of the inclination with respect to the “oblique direction”, it can be said that the majority of the sign related to the periphery of the first magnetization fixed region 11 is opposite to the majority of the sign related to the periphery of the second magnetization fixed region 12. .

3-7. Seventh Embodiment FIG. 18 is a plan view showing initialization of a magnetic recording layer 10 in a seventh embodiment. In FIG. 18, the first magnetization fixed region 11, the second magnetization fixed region 12, and the magnetization switching region 13 have a rectangular shape. The first magnetization fixed region 11 and the second magnetization fixed region 12 are mirror-symmetric with respect to the Y axis, and have a long side along the Y axis and a short side along the X axis. On the other hand, the magnetization switching region 13 has a long side along the X axis and a short side along the Y axis. Further, the magnetization switching region 13 is gently connected to the first magnetization fixed region 11 through the wide connection portion 14. Therefore, the pin potential between the first magnetization fixed region 11 and the magnetization switching region 13 is relatively small compared to the second magnetization fixed region 12 side.

  As in the case of the sixth embodiment, the first external magnetic field is applied in an oblique direction intersecting with both the X axis and the Y axis. When the application of the first external magnetic field is stopped, as shown in the state (C1), the magnetization 90-1 of the first magnetization fixed region 11 and the magnetization 90-2 of the second magnetization fixed region 12 are -Z. Turn to the direction. On the other hand, the magnetization 90-3 of the magnetization switching region 13 faces the + Z direction. Accordingly, two domain walls DW 1 and DW 2 are generated in the magnetic recording layer 10.

  Thereafter, a second external magnetic field (Hz) in the + Z direction is applied. Then, the domain walls DW1 and DW2 try to enter the first magnetization fixed region 11 and the second magnetization fixed region 12, respectively. The threshold magnetic field required for the domain wall to enter each magnetization fixed region is smaller on the first magnetization fixed region 11 side having a loose connection than on the second magnetization fixed region 12 side. Therefore, when the magnitude of the second external magnetic field is set in the middle of the two threshold magnetic fields, only the domain wall DW1 enters the first magnetization fixed region 11 and exits from the left side of the first magnetization fixed region 11. That is, as indicated by the state (C2), only the magnetization 90-1 of the first magnetization fixed region 11 is reversed in the + Z direction. As a result, one domain wall DW2 remains only between the second magnetization fixed region 12 and the magnetization switching region 13. That is, the magnetic recording layer 10 is initialized.

3-8. Generalized Magnetized Region FIG. 19 is a plan view for explaining initialization for the generalized magnetized region. The magnetized region has N sides, which are represented by vectors L ₁ , L ₂ ,..., L _N , respectively. For each side, the normalization normal vectors going into the region are represented by n ₁ , n ₂ ,..., _{N N.} The normalization vector of the first external magnetic field for initialization is h _ext . It is assumed that the magnetization region has a magnetization vector M parallel to the normalized vector h _ext by application of the first external magnetic field. In this case, demagnetizing field at the side _{L i} vicinity of i-th (i = 1 to N) is parallel to the normalized perpendicular vector _{n i,} the inner product of the size, including the codes, M and _{n i} (- M · n _i ). At this time, a vector T expressed by the following equation (2) can be defined.

Vector T is given by the sum of the lengths of the product of the normalized torque and Kakuhen L _i at the sides L _i vicinity. Here, it is considered that the magnetization vector M is parallel to the normalized vector h _ext . If the direction of the vector T is the + Z direction, it means that the torque in the + Z direction is the majority. In that case, after the application of the first external magnetic field stops, the magnetization of the magnetization region faces the + Z direction. On the other hand, when the direction of the vector T is the −Z direction, it means that the torque in the −Z direction is the majority. In that case, after the application of the first external magnetic field is stopped, the magnetization of the magnetization region faces the −Z direction.

  In the embodiment of the present invention, the majority of the torque in the first magnetization fixed region 11 is opposite to the majority of the torque in the second magnetization fixed region 12. In other words, the direction of the vector T related to the first magnetization fixed region 11 is opposite to the direction of the vector T related to the second magnetization fixed region 12. In addition, since a magnetic pole does not generate | occur | produce in the part which overlaps 1st boundary B1 and 2nd boundary B2 among the periphery of magnetization fixed area | regions 11 and 12, it is not necessary to include the part in the said sum.

4). Circuit Configuration of MRAM FIG. 20 shows an example of the configuration of the MRAM in this embodiment. In FIG. 20, an MRAM 200 has a memory cell array 201 in which a plurality of magnetic memory cells 1 are arranged in a matrix. The memory cell array 201 includes a reference cell 1r that is referred to when reading data together with the magnetic memory cell 1 used for data recording. The structure of the reference cell 1r is the same as that of the magnetic memory cell 1.

  Each magnetic memory cell 1 has select transistors TR1 and TR2 in addition to the magnetoresistive elements shown in the foregoing embodiments. One of the source / drain of the selection transistor TR1 is connected to the first magnetization fixed region 11 via the first wiring 41 (see FIG. 5), and the other is connected to the first bit line BL1. One of the source / drain of the selection transistor TR2 is connected to the second magnetization fixed region 12 via the second wiring 42, and the other is connected to the second bit line BL2. The gates of the selection transistors TR1 and TR2 are connected to the word line WL. The pinned layer 30 of the magnetoresistive element is connected to the ground via a read wiring 50 (see FIG. 5).

  The word line WL is connected to the X selector 202. The X selector 202 selects a word line WL connected to the target memory cell 1s as a selected word line WLs in data writing / reading. The first bit line BL1 is connected to the Y-side current termination circuit 204, and the second bit line BL2 is connected to the Y selector 203. The Y selector 203 selects the second bit line BL2 connected to the target memory cell 1s as the selected second bit line BL2s. The Y-side current termination circuit 204 selects the first bit line BL1 connected to the target memory cell 1s as the selected first bit line BL1s.

  The Y-side current source circuit 205 supplies or draws a predetermined write current to the selected second bit line BL2s during data writing. The Y-side power supply circuit 206 supplies a predetermined voltage to the Y-side current termination circuit 204 at the time of data writing. As a result, the write current flows into or out of the Y selector 203. These X selector 202, Y selector 203, Y side current termination circuit 204, Y side current source circuit 205, and Y side power supply circuit 206 form a “write current supply circuit” for supplying a write current to the magnetic memory cell 1. It is composed.

  When reading data, the first bit line BL1 is set to “Open”. The read current adding circuit 207 supplies a predetermined read current to the selected second bit line BL2s. Further, the read current adding circuit 207 supplies a predetermined current to the reference second bit line BL2r connected to the reference cell 1r. The sense amplifier 208 senses the data of the target memory cell 1s based on the difference between the potential of the reference second bit line BL2r and the potential of the selected second bit line BL2s, and outputs the data.

5). Other Application Examples The present invention can also be applied to magnetic recording devices other than MRAM. For example, FIG. 21 shows a magnetic recording layer having perpendicular magnetic anisotropy. This magnetic recording layer is formed in parallel with the XY plane. The magnetic recording layer has a plurality of magnetization regions 70A to 70E connected in series.

  The magnetization 71A of the magnetization region 70A is fixed in the −Z direction. The magnetization 71B of the magnetization region 70B is fixed in the + Z direction. The magnetization 71C of the magnetization region 70C is fixed in the −Z direction. The magnetization 71D of the magnetization region 70D is fixed in the + Z direction. The magnetization 71E of the magnetization region 70E is fixed in the −Z direction. That is, the magnetization of the magnetic recording layer is alternately fixed in the + Z direction and the −Z direction. Therefore, the domain wall DW is formed between the adjacent magnetization regions 70.

  For example, the magnetization regions 70A, 70C, and 70E have the same planar shape as that of the first magnetization fixed region 11 shown in FIG. On the other hand, the magnetization regions 70B and 70D have the same planar shape as the second magnetization fixed region 12 in FIG. Therefore, the magnetization state shown in FIG. 21 can be easily obtained by the same initialization method as in FIG. That is, initialization of the magnetic recording layer having perpendicular magnetic anisotropy can be easily performed. The planar shapes of the magnetized regions 70A to 70E are not limited to those shown in FIG.

  Further, the basic principle of the present invention, that is, the method of initializing magnetization in a desired direction using the torque by the demagnetizing field can be applied to a magnetization region having in-plane magnetic anisotropy.

  The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the above-described embodiments, and can be appropriately changed by those skilled in the art without departing from the scope of the invention.

  This application claims the priority on the basis of the Japan patent application 2007-206143 for which it applied on August 8, 2007, and takes in those the indications of all here.

Claims (15)

Comprising a magnetic recording layer which is a ferromagnetic layer having perpendicular magnetic anisotropy,
The magnetic recording layer is
A magnetization reversal region;
A first magnetization fixed region connected to a first boundary of the magnetization switching region and having a magnetization direction fixed in a first direction;
A second magnetization fixed region connected to a second boundary of the magnetization switching region and having a magnetization direction fixed in a second direction opposite to the first direction;
In the plane where the magnetic recording layer is formed, when the sign of the tangential slope with respect to the periphery of the magnetic recording layer is considered, the majority of the sign related to the first magnetization fixed region is related to the second magnetization fixed region. A magnetic recording device that is the opposite of the majority of the sign. A magnetic recording apparatus according to claim 1,
In the XYZ coordinate system, the magnetic recording layer is formed parallel to the XY plane, the Z axis is orthogonal to the XY plane, and the X axis connects the first boundary and the second boundary with the shortest distance. Parallel to the line, the Y axis is orthogonal to the X axis and the Z axis,
The first direction and the second direction are substantially parallel to the Z-axis,
The inclination is a finite inclination of the tangent to the X axis or the Y axis. A magnetic recording apparatus according to claim 2,
The first magnetization fixed region has a first side intersecting with the Y axis,
The second magnetization fixed region has a second side intersecting the Y axis,
The magnetic recording apparatus, wherein the sign of the inclination of the first side is opposite to the sign of the inclination of the second side. A magnetic recording apparatus according to claim 3, wherein
The first magnetization fixed region and the second magnetization fixed region have a parallelogram shape in the XY plane. A magnetic recording device according to claim 3 or 4,
In the XY plane, at least one side of the magnetization switching region is connected to the first side and the second side. A magnetic recording apparatus according to claim 2,
The first magnetization fixed region has a third side facing the first boundary,
The second magnetization fixed region has a fourth side facing the second boundary,
The magnetic recording apparatus, wherein the sign of the inclination of the third side is opposite to the sign of the inclination of the fourth side. A magnetic recording apparatus according to claim 2,
The sign of the inclination of all sides of the first magnetization fixed region is opposite to the sign of the inclination of all sides of the second magnetization fixed region. A magnetic recording apparatus according to claim 2,
A magnetic recording apparatus, wherein a periphery of at least one of the first magnetization fixed region and the second magnetization fixed region includes a curve. A magnetic recording apparatus according to any one of claims 2 to 8,
In the XY plane, the first magnetization fixed region has a first shape, the second magnetization fixed region has a second shape,
The first shape and the second shape are mirror-symmetric with respect to the Y axis. A magnetic recording device according to any one of claims 2 to 9,
In the XY plane, at least one side of the magnetization switching region intersects both the X axis and the Y axis. Comprising a magnetic recording layer which is a ferromagnetic layer having perpendicular magnetic anisotropy,
The magnetic recording layer is
A magnetization reversal region;
A first magnetization fixed region connected to a first boundary of the magnetization switching region and having a magnetization direction fixed in a first direction;
A second magnetization fixed region connected to a second boundary of the magnetization switching region and having a magnetization direction fixed in a second direction opposite to the first direction;
In the plane on which the magnetic recording layer is formed, the first magnetization fixed region and the second magnetization fixed region have a rectangular shape,
The direction in which the short side of the first magnetization fixed region extends is perpendicular to the direction in which the short side of the second magnetization fixed region extends. A magnetic recording apparatus according to any one of claims 1 to 11,
The magnetic recording device is a domain wall motion type magnetic random access memory,
A magnetic recording device in which a domain wall is formed at the first boundary or the second boundary of the magnetic recording layer. Comprising a magnetic recording layer which is a ferromagnetic layer having perpendicular magnetic anisotropy,
The magnetic recording layer has a first magnetization fixed region and a second magnetization fixed region,
Majority of the sign of the outer product of the magnetization of the first magnetization fixed region and the demagnetizing field generated at the end of the first magnetization fixed region when an external magnetic field parallel to the surface on which the magnetic recording layer is formed is applied Is the opposite of the majority of the sign of the outer product of the direction of magnetization of the second magnetization fixed region and the demagnetizing field generated at the end of the second magnetization fixed region. A magnetization pinning method in a magnetic recording layer which is a ferromagnetic layer having perpendicular magnetic anisotropy,
The magnetic recording layer has a first magnetization fixed region and a second magnetization fixed region,
The magnetization fixing method includes:
Applying a first external magnetic field parallel to the surface on which the magnetic recording layer is formed;
Here, the majority of the sign of the outer product of the magnetization of the first magnetization fixed region and the demagnetizing field generated at the end of the first magnetization fixed region is the magnetization of the second magnetization fixed region and the second magnetization fixed region. Is the opposite of the majority of the sign of the outer product with the demagnetizing field generated at the end of
Stopping the application of the first external magnetic field. A magnetization fixing method according to claim 14, wherein
The method of pinning magnetization further includes the step of applying a second external magnetic field orthogonal to the surface on which the magnetic recording layer is formed.

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