JP2010114261A - Magnetic memory and method for recording information to the magnetic memory - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic memory, capable of rewriting magnetic recording information without carrying a high density current, or employing a high coersive force material on a part for holding magnetic information. <P>SOLUTION: The magnetic memory 1 includes a magnetic-wall moving layer 111; non-magnetic substance layer 112 as an intermediate layer; a magnetoresistance effect element 11 stacked with a fixed layer 113; and heating parts 12A and 12B, locally heating the magnetic-wall moving layer 111. In the magnetic-wall moving layer 111, an axis of easy magnetization is disposed in the in-plane direction of the magnetic-wall moving layer 111, and a magnetic wall 51 is formed in the magnetic-wall moving layer 111; and the magnetic wall moves in the magnetic wall moving layer, by the local heating of the magnetic-wall moving layer with the heating parts 12A, 12B. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic memory including a domain wall moving layer for holding magnetic information, and an information recording method for recording magnetic information in the magnetic memory.

  An MRAM (Magnetic Random Access Memory) is known as a magnetic memory that records magnetic information in a magnetoresistive effect element. In particular, it is known that an MRAM using a tunnel magnetoresistive effect element can obtain a high magnetoresistive effect. As a method of recording magnetic information in the MRAM, a current line for generating a magnetic field is arranged in the immediate vicinity of the magnetoresistive effect element, and the magnetic information is applied by applying a magnetic field larger than the coercive force of the magnetic layer holding the information. A method of recording is known.

  As another method for recording magnetic information in the MRAM, for example, a magnetic information recording method called spin injection magnetization reversal is known. Patent Document 1 discloses a magnetoresistive effect element capable of recording magnetic information by a magnetic information recording method by spin injection magnetization reversal. FIG. 14 is a cross-sectional view showing the magnetoresistive effect element described in Patent Document 1. As shown in FIG. 14, the magnetoresistive element 210 described in Patent Document 1 includes a memory magnetic film 211, a spacer 212, and a reference magnetic film 213. In the magnetic information recording method by spin injection magnetization reversal, a current is directly applied to the magnetoresistive effect element 210, and spin torque generated by spin polarization of the current is used to store information in the storage magnetic film 211 that holds information. Magnetization reversal is performed and magnetic information is recorded.

Further, as another magnetic memory, Patent Document 2 discloses a magnetic memory in which magnetic information is recorded on a magnetic material formed in a thin line, and recording or reproduction is performed while moving the recorded information in the thin line. . In the magnetic memory described in Patent Document 2, a current is passed through a fine wire-like magnetic material, spin current is generated by spin-polarizing the current, and a magnetic domain to be recorded is recorded by moving a domain wall in the fine wire. After moving to the position of the device, information is recorded by applying a magnetic field from the recording device. Further, it is disclosed that reproduction of recorded information is performed using a magnetoresistive effect element.
JP 2005-93488 A (published April 7, 2005) US Pat. No. 6,834,005 (registered on Dec. 21, 2004)

  However, the conventional magnetic memory has the following problems. That is, the magnetic information generated by applying the magnetic field generated from the current line to the MRAM that records the magnetic information by applying the magnetic field generated from the above-described conventional current line or the thin line-shaped magnetic material as disclosed in Patent Document 2 is used. In a magnetic memory for recording, when a high coercive force material that can stably hold magnetic information is used for a portion that holds magnetic information, a recording magnetic field generated from a current line is insufficient and recording becomes difficult. Therefore, there is a problem that a high coercive force material that can stably hold magnetic information cannot be used for a portion that holds magnetic information.

Further, in the MRAM disclosed in Patent Document 1, since magnetization is reversed by passing a current directly through the magnetoresistive effect element, in order to generate a magnetic torque that causes magnetization reversal, 1 × 10 ⁶ A / cm ^2. It is necessary to energize a current having a high current density that exceeds. For this reason, there is a problem that the durability of the magnetic memory may be lowered, such as causing dielectric breakdown of the magnetoresistive effect element when rewriting is performed repeatedly.

  The present invention has been made in view of the above-mentioned conventional problems, and the object thereof is not to energize a magnetoresistive effect element with a high current density, and a high coercive force material is provided in a part for holding magnetic information. It is an object of the present invention to provide a magnetic memory that can be used.

  In order to solve the above problems, a magnetic memory according to the present invention includes a magnetoresistive effect element in which a domain wall motion layer, a nonmagnetic material layer as an intermediate layer, and a fixed layer are laminated, and the domain wall motion layer is locally disposed. A heating part that can be heated automatically, and in the domain wall motion layer, the easy axis of magnetization is located in an in-plane direction of the domain wall motion layer, and the domain wall motion layer has a domain wall formed by the heating unit. The domain wall moving layer is locally heated, so that the domain wall moves in the domain wall moving layer.

  As described above, according to the magnetic memory of the present invention, in the domain wall motion layer, the easy magnetization axis is located in the in-plane direction of the domain wall motion layer, and the domain wall motion layer is formed with the domain wall. . For this reason, when the domain wall motion layer is locally heated by the heating unit, the coercivity of the heated region is reduced. Thereby, the domain wall driving force generated by the energy gradient and the force generated by the leakage magnetic field are applied to the domain wall, so that the domain wall can be moved to the heated region, and the magnetic resistance can be changed.

  Therefore, since the magnetic recording information can be rewritten by the heat from the heating unit, the magnetic recording information can be rewritten without passing a high current density current through the magnetoresistive element. Further, since the magnetic recording information is rewritten by heat, a high coercive force material can be used for the domain wall moving layer, and information can be stably maintained. Furthermore, since magnetic recording information can be rewritten without passing a current having a high current density through the magnetoresistive element, a magnetic memory having excellent durability can be provided.

  In the magnetic memory of the present invention, it is preferable that a plurality of the heating units are provided.

  In the magnetic memory of the present invention, the domain wall can be moved to the heated region by heating the domain wall moving layer. Therefore, by providing a plurality of heating units, the heated region is provided at a plurality of locations. Can be generated. Thereby, since the domain wall can be moved toward each heated region, the position of the domain wall can be changed stepwise. Therefore, a magnetic memory capable of multi-value recording can be provided.

  In the magnetic memory of the present invention, when the direction perpendicular to the domain wall is defined as the length direction, the length of the domain wall moving layer is longer than the length of the nonmagnetic layer, and the length of the heating unit is The center position is preferably formed outside the region where the domain wall motion layer and the nonmagnetic layer overlap.

  According to the above invention, since the heating part is formed outside the region where the domain wall moving layer and the nonmagnetic layer overlap, the domain wall can be moved outside the region by heating by the heating unit. Thereby, the magnetization direction of the domain wall moving layer region contributing to the change of the magnetic resistance, that is, the inner region of the domain wall moving layer on the surface in contact with the non-magnetic layer can be made one direction. Therefore, it is possible to provide a magnetic memory capable of obtaining a large magnetoresistance effect when detecting the magnetoresistance effect.

  In the magnetic memory of the present invention, it is preferable that a plurality of the domain walls are formed, and energizing means for moving the whole of the plurality of domain walls in the domain wall moving layer is connected to the domain wall moving layer.

  According to the above invention, since the whole of the plurality of domain walls can be moved in the domain wall moving layer by the energization means, even if the number of installed heating parts is as small as one, the domain wall at a desired position is individually In addition, it can be moved with a desired width.

  In the magnetic memory of the present invention, it is preferable that the heating section generates heat by generating Joule heat and locally heats the domain wall motion layer.

  According to the above invention, a magnetic memory including a heating unit that generates heat with a small current can be easily configured.

  In the magnetic memory of the present invention, it is preferable that the heating unit generates heat by light irradiation and locally heats the domain wall motion layer.

  According to the above invention, since the heating part can be heated and cooled at high speed, high-speed recording is possible.

  The information recording method to the magnetic memory according to the present invention is a method of locally heating the domain wall motion layer with respect to the magnetic memory and moving the domain wall in the domain wall motion layer.

  According to the above method, since the domain wall is moved by local heating of the domain wall moving layer, it is possible to perform magnetic information recording in the magnetic memory without using magnetic field application by current or spin injection. Therefore, even with a high coercive force material that can stably hold magnetic information, magnetic information can be recorded, and magnetic information can be recorded without passing a current having a high current density. be able to.

  As described above, in the magnetic memory of the present invention, in the domain wall motion layer, the easy axis of magnetization is located in the in-plane direction of the domain wall motion layer, the domain wall motion layer has a domain wall, and the heating unit Thus, the domain wall moving layer is locally heated, so that the domain wall moves in the domain wall moving layer.

  Therefore, there is an effect that it is possible to rewrite information without passing a current having a high current density, and to provide a magnetic memory excellent in durability and retention stability of magnetic information.

[Embodiment 1]
An embodiment of the present invention will be described with reference to FIGS. 1 to 8 as follows. FIG. 1 is a cross-sectional view showing a configuration of a magnetic memory 1 according to the present embodiment. The magnetic memory 1 includes a magnetoresistive effect element 11 in which a domain wall motion layer 111, a nonmagnetic material layer 112 as an intermediate layer, and a fixed layer 113 are stacked, and a heating unit 12A for heating the domain wall motion layer 111. And a heating unit 12B, a power source 13 for energizing the heating unit 12A and the heating unit 12B, and an upper electrode 114 and a lower electrode 115 for detecting the magnetoresistive effect of the magnetoresistive effect element 11.

  The domain wall motion layer 111 has an easy axis of magnetization in the in-plane direction, and a domain wall 51 is formed at the boundary where the magnetization direction in the domain is reversed. The domain wall 51 is positioned perpendicular to the surface direction of the domain wall moving layer 111, and both ends of the domain wall 51 reach opposite side surfaces of the domain wall moving layer 111. That is, in the domain wall moving layer 111, two magnetic domains 52A and 52B having magnetizations opposite to each other across the domain wall 51 are formed. The magnetic memory 1 according to the first embodiment has the above configuration, and each component will be described below. In addition, the arrow in FIG. 1 represents the direction of total magnetization.

  The domain wall motion layer 111 is an in-plane magnetization layer having an easy axis of magnetization in the in-plane direction, and a single layer or a plurality of layers of rare earth-transition metal materials that can be heated near the high magnetic permeability material or the Curie temperature. Can be formed. As a specific material, Fe, NiFe, NiFeTa, Co, CoFe, and CoFeB, or an alloy material mainly composed of these materials can be used. An alloy material in which one or more of Gd, Tb, Dy, and Ho and one or more of Fe, Co, and Ni are combined can also be used. In order to smoothly move the domain wall 51 of the domain wall moving layer 111, it is more preferable to use an amorphous magnetic material having no crystal grains.

Among the above materials, when a rare earth-transition metal material exhibiting ferrimagnetism is used, the coercive force at room temperature can be increased, and magnetic information is stably maintained. When the rare earth-transition metal material exhibiting ferrimagnetism is applied, the composition of the material away from the compensation temperature is set so that the easy axis of magnetization of the domain wall motion layer 111 is in the in-plane direction. Specifically, when the material uniaxial anisotropy constant is K _u and the saturation magnetization is M _s , the material composition is set so that K _u −2πM _S ² is negative in the range from room temperature to the highest heating temperature. decide.

  The thickness of the domain wall moving layer 111 is not particularly limited as long as the domain wall 51 can be formed and the domain wall 51 can be moved with heating, but for example, 5 nm or more and 70 nm or less. It is desirable to do. If the thickness of the domain wall moving layer 111 is less than 5 nm, the domain wall 51 may not move smoothly due to the unevenness of the film. On the other hand, if the thickness is greater than 70 nm, a plurality of magnetic domains may be formed in the film thickness direction.

  Further, in the domain wall moving layer 111 of FIG. 1, the magnetization direction is set so that the magnetization is located in the opposite direction across the domain wall 51 (so that the magnetic poles are abutted). In order to realize this, the domain wall moving layer 111 has a smaller width and thickness (depth direction and vertical direction in FIG. 1) than the length in the direction in which the domain wall 51 moves (length in the horizontal direction in FIG. 1). It is formed so that shape anisotropy occurs.

  As the nonmagnetic layer 112, a nonmagnetic metal material, an insulator material, or a combination thereof can be used. When a nonmagnetic metal material is used, the magnetic memory 1 functions as a CPP-GMR (Current Perpendicular to Plane-Giant Magneto-resistive) element, and when an insulator material is used, a TMR (Tunneling Magneto-resistive) is used. Functions as an element.

As an example of a specific material of the nonmagnetic layer 112, for example, an alloy material in which one kind or a plurality of kinds of Cu, Al, Mg, Al ₂ O ₃ and MgO is combined can be used. Among these, when MgO is used as the material of the nonmagnetic layer 112, the magnetoresistive element 11 is particularly preferable because it is known that a particularly high magnetoresistive effect can be obtained. The film thickness of the nonmagnetic layer 112 is preferably 0.5 nm or more and 5 nm or less from the viewpoint of obtaining a practically large magnetoresistive effect.

  The fixed layer 113 is an in-plane magnetic layer in which the direction of magnetization is fixed in one direction, and is composed of a single layer or a plurality of layers of magnetic materials. When the fixed layer 113 is formed as a single layer, it is desirable to use a ferromagnetic material having a coercive force larger than that of the domain wall moving layer 111. For example, Fe, Co, or a combination thereof may be Pt, Pd, B, or the like. A material added with TbFeCo or DyFeCo can be used.

  In the case where the fixed layer 113 is formed of a plurality of layers of magnetic materials, a material in which the magnetization of a low coercive force material typified by CoFeB is fixed by an antiferromagnetic material typified by MnPt or MnIr can be applied. The film thickness of the fixed layer 113 is desirably 10 nm or more and 50 nm or less from the viewpoint of stably maintaining the magnetization in one direction. The material and composition of the fixed layer 113 are selected so that the magnetization direction fixed in one direction does not change irreversibly with heating by the heating unit 12A or the heating unit 12B.

  The size of the magnetoresistive element 11 in the length direction and width direction (left and right direction and depth direction in the drawing) is not particularly limited as long as the function as the magnetic memory 1 can be realized. Absent. For example, the length direction (left-right direction in the drawing) is 100 nm or more and 2 μm or less, and the length in the width direction (drawing depth direction) is, for example, 20 nm or more and 500 nm or less, and the height direction (up-down direction in the drawing). ) Corresponds to the total film thickness of the domain wall motion layer 111, the nonmagnetic material layer 112, and the fixed layer 113, and can be formed to be, for example, 15.5 nm or more and 125 nm or less.

  In addition, it can be said that the length direction of the magnetoresistive effect element 11 is a direction orthogonal to the surface of the domain wall 51 in other words. In other words, the width direction of the magnetoresistive element 11 can be said to be the direction of a straight line where the surface where the domain wall moving layer 111 and the nonmagnetic layer 112 are in contact with the surface of the domain wall 51 intersects. Furthermore, it can be said that the height direction of the magnetoresistive effect element 11 is, in other words, a direction orthogonal to the surface where the domain wall motion layer 111 and the nonmagnetic material layer 112 are in contact with each other.

  The heating unit 12 </ b> A and the heating unit 12 </ b> B are members that locally heat the domain wall motion layer 111. In the magnetic memory 1, the heating unit 12 </ b> A and the heating unit 12 </ b> B are disposed on the domain wall motion layer 111 via the upper electrode 114. The heating units 12A and 12B are electrically connected to the power source 13.

  The heating unit 12A and the heating unit 12B are not particularly limited as long as the domain wall moving layer 111 can be locally heated. For example, NiCr alloy, Pt, Mo, Ta, W, SiC, MoSi, or conductive carbon can be applied. Further, the heating unit 12A and the heating unit 12B are configured with an electric circuit so that a current can be supplied from the power source 13, and can be switched as necessary.

  In this embodiment, a resistance heating element that generates Joule heat is used as the heating unit 12A and the heating unit 12B, whereby a magnetic memory including a heating unit that generates heat with a small current can be easily configured. Note that the present invention is not limited to this as long as the domain wall motion layer 111 can be locally heated. For example, a heating unit that generates heat by light irradiation may be used. In this case, the heating unit can be heated and cooled at a higher speed than the heating unit using Joule heat, and high-speed recording is possible. For example, a semiconductor laser can be used for the light irradiation.

  The upper electrode 114 and the lower electrode 115 are used to detect a change in magnetoresistance of the magnetoresistive effect element 11. Specifically, energization is performed between the upper electrode 114 and the lower electrode 115, and the magnetoresistance value of the magnetoresistive effect element 11, that is, magnetic information is detected. The upper electrode 114 and the lower electrode 115 are not particularly limited, and conventionally known electrodes used for magnetic memories can be used.

  Although omitted in FIG. 1, the periphery of each member of the magnetic memory 1, between the domain wall motion layer 111 and the heating unit 12A or the heating unit 12B, the upper electrode 114, the heating unit 12A or the heating unit. 12B may be protected by an insulator protective film from the viewpoint of preventing unnecessary energization between members and protecting the magnetic memory 1.

  In the information recording in the magnetic memory 1 according to the first embodiment, the heating unit 12A or the heating unit 12B is energized by the power source 13 to generate Joule heat, and the domain wall moving layer 111 is locally heated, so that the domain wall 51 is This is done by moving toward the center of heating. The heating center refers to a portion having the highest temperature heated by the heating unit 12A or the heating unit 12B. When the direction orthogonal to the domain wall 51 is a length direction, the heating unit 12A and the heating unit 12B The center position in the length direction.

  Thereby, in the domain wall moving layer 111, the area ratio of the two magnetic domains 52A and 52B existing across the domain wall 51 is changed, and a change in magnetoresistance is obtained. As described above, information is recorded by changing the magnetic resistance in accordance with the position of the domain wall 51 of the domain wall moving layer 111. On the other hand, if the other heating unit 12B or the heating unit 12A that is not energized is energized and the domain wall moving layer 111 is locally heated, the domain wall 51 can be moved to another position.

  2A to 2C are cross-sectional views of the domain wall motion layer 111 for illustrating the principle of recording magnetic information in the magnetic memory 1 according to the first embodiment. For convenience of explanation, only the domain wall motion layer 111 is extracted from the magnetic memory 1 and described. In FIG. 2, the center part of the range (temperature rise range) sandwiched between broken lines corresponds to the heating center of the heating part 12A and the heating part 12B. That is, when the region sandwiched by the broken line is heated by the heating unit, the temperature of the domain wall motion layer 111 rises locally around the center of the range sandwiched by the broken line. Hereinafter, a portion where the temperature is increased by heating is defined as a temperature increase region. A method for simultaneously moving the domain wall 51, that is, a method for recording information in a magnetic memory will be described with reference to FIG. The information recording method to the magnetic memory according to the present embodiment is a method in which the magnetic wall moving layer is locally heated with respect to the magnetic memory by the heating unit, and the domain wall is moved in the domain wall moving layer. is there.

  In the magnetic memory 1 according to the first embodiment, as shown in FIG. 2A, the magnetic domains 52 </ b> A and 52 </ b> B having opposite magnetization directions exist with the domain wall 51 interposed therebetween. Here, both ends of the domain wall 51 reach opposite side surfaces of the domain wall moving layer 111, and the magnetic domain 52A and the magnetic domain 52B are formed with the domain wall 51 as a boundary (becomes open domain walls). Further, the magnetization of the magnetic domain 52A is larger than the magnetization of the magnetic domain 52B.

  Information recording on the domain wall motion layer 111 is performed by locally heating the domain wall motion layer 111. That is, in the first embodiment, when the heating unit 12A or the heating unit 12B is energized and Joule heat is generated, the local part of the domain wall motion layer 111 is heated. By this local heating, the magnetization of the heated region of the domain wall motion layer 111 can be brought close to the Curie temperature of the domain wall motion layer 111, so that the magnetic anisotropy can be weakened. As a result, the domain wall driving force generated when a change (gradient) in magnetization anisotropy occurs in the direction orthogonal to the domain wall 51 and the force generated by the leakage magnetic field from the magnetic domain 52A and the magnetic domain 52B (dipole interaction). Are added to the domain wall 51.

  The domain wall driving force refers to a high temperature region (near the heating center) of the domain wall moving layer 111 by weakening the magnetic anisotropy of the temperature rising region of the domain wall moving layer 111 by heating of the heating unit 12A or the heating unit 12B. It is a force generated by a change (gradient) in magnetic anisotropy between the low temperature region. Since the domain wall motion layer 111 is an in-plane magnetization layer, a domain wall energy gradient occurs in the length direction (the left-right direction in the drawing) of the domain wall motion layer 111 with the domain wall 51 in between, and the side with the higher magnetic anisotropy (temperature) Domain wall driving force corresponding to ∂σ / ∂x works from a region having a low magnetic anisotropy to a region having a low magnetic anisotropy (a region having a high temperature). σ is the domain wall energy, and x is the length in the direction orthogonal to the surface of the domain wall 51 (the horizontal direction in the drawing). In FIG. 2B, the region sandwiched between the broken lines is heated, and the region sandwiched between the broken lines is a temperature rise region.

  The force generated by the leakage magnetic field (dipole interaction) is the magnetic domains 52A and 52B facing each other across the domain wall 51 toward the temperature rising region, as indicated by an arc-shaped arrow in FIG. Force generated by the leakage magnetic field generated from

  When the sum of the domain wall driving force due to the gradient of the domain wall energy and the force (dipole interaction) generated by the leakage magnetic field exceeds the coercive force of the domain wall moving layer 111 at the domain wall 51 position, the domain wall 51 undergoes magnetization reversal. Then, the movement of the domain wall 51 stops at a position where the magnetic wall moves toward the high temperature region of the domain wall moving layer 111 and no force is applied to the domain wall 51, that is, at the heating center (position where the temperature is highest). In this state, the energization of the heating unit 12A or the heating unit 12B is stopped, and the heating is terminated, whereby the domain wall moving layer 111 is cooled and stabilized, and the domain wall 51 from the original position as shown in FIG. Is fixed in a moved state.

  As described above, according to the magnetic memory 1 according to the present embodiment, in the domain wall motion layer 111, the easy axis of magnetization is located in the in-plane direction of the domain wall motion layer, and the domain wall motion layer 111 includes the domain wall 51. Is formed. For this reason, when the domain wall motion layer 111 is locally heated by the heating unit 12A or the heating unit 12B, the coercivity of the heated region is reduced. Thereby, the domain wall driving force generated by the energy gradient and the force (dipole interaction) generated by the leakage magnetic field are applied to the domain wall 51, so that the domain wall 51 can be moved to the heating center. That is, since the area ratio between the magnetic domains 52A and 52B can be changed, the magnetic resistance can be changed.

  Therefore, the magnetic recording information can be rewritten by the heat of the heating unit 12A or the heating unit 12B. That is, when rewriting the magnetic information, the domain wall moving layer can be formed without directly flowing a high current density current to the magnetoresistive effect element. Since magnetic recording information can be rewritten by partially reversing magnetization, a magnetic memory having excellent durability can be provided. In addition, since magnetic recording information is rewritten by heat, a high coercive force material can be used, and information can be stably maintained.

  In order to return from the state shown in FIG. 2C to the state shown in FIG. 2A, the domain wall moving layer 111 is heated so that the domain wall 51 shown in FIG. 2A moves to the heating center. Then, the temperature rise region may be set so that the temperature rise region accompanying heating includes the domain wall 51 shown in FIG. In this way, by setting the position of the domain wall 51 to the state shown in FIG. 2A or 2C, the area ratio between the magnetic domain 52A and the magnetic domain 52B can be changed, and a change in magnetic resistance is obtained. It becomes possible.

  Note that the Curie temperature of the magnetic material used for the domain wall motion layer 111 may be locally exceeded in the high temperature portion of the temperature rise region. In this case, the domain wall 51 moves during the cooling process after heating, and finally the domain wall 51 is formed at the center position as in FIG.

  Further, when the domain wall 51 is moved, heating is performed so that at least a part of the opposing magnetic domains 52A and 52B remains, in other words, either or both of the magnetic domains 52A and 52B are not completely lost. I do. In addition, the domain wall 51 is included in the temperature increase range accompanying heating.

  Further, from the viewpoint of reducing the coercive force of the domain wall moving layer 111 with respect to the force applied to the domain wall 51 by heating (the sum of the domain wall driving force and the force due to the dipole interaction), the domain wall moving layer 111 is heated to a temperature close to the Curie temperature. It is desirable to be able to. On the other hand, if the Curie temperature is too low, it is difficult to control the heating temperature, and it becomes difficult to obtain a sufficient domain wall driving force. From these viewpoints, it is highly desirable that the Curie temperature of the domain wall motion layer 111 is 100 ° C. or more and 600 ° C. or less. When the fixed layer 113 is configured to include the Mn-based antiferromagnetic layer used in the general magnetoresistive effect element 11, the antiferromagnetic layer generally has a blocking temperature of about 400 ° C. or lower. For this reason, the heating temperature of the domain wall motion layer 111 is also limited to about 400 ° C. or less.

  The recorded information can be read out by detecting the magnetoresistance by energizing between the upper electrode 114 and the lower electrode 115.

  In manufacturing the magnetic memory 1 of the present embodiment, a known MRAM or a process for manufacturing a magnetoresistive element can be applied. An example thereof is shown in FIGS. FIGS. 3A to 3E are cross-sectional views showing a manufacturing process of a magnetic memory showing an embodiment of a method of manufacturing a magnetic memory according to the present invention.

  First, as shown in FIG. 3A, the lower electrode 115, the fixed layer 113, the nonmagnetic layer 112, the domain wall motion layer 111, the insulator protective film 116, and the heating unit 12 are formed on a substrate (not shown). Thereafter, as shown in FIG. 3B, these stacked bodies are patterned using photolithography, electron beam lithography, or FIB (Focused Ion Beam). At this time, the laminate constituted by the domain wall motion layer 111 to the lower electrode 115, the insulator protective film 116, and the heating unit 12 are separately patterned, and the heating unit 12A and the heating unit 12A are formed on a part of the laminate. The heating part 12B is formed.

  Subsequently, as shown in FIG. 3C, after forming the insulator protective film 116 for preventing contact between the heating unit 12A and the heating unit 12B and the upper electrode 114, photolithography, electron The insulator protective film 116 where the upper electrode 114 is formed on the domain wall motion layer 111 is removed by line lithography or FIB. Subsequently, as shown in FIG. 3D, the upper electrode 114 is formed on the domain wall motion layer 111 to complete the shape of the magnetic memory 1 in the first embodiment.

  Subsequently, as shown in FIG. 3E, after fixing the magnetization direction of the fixed layer 113, initialization for forming the domain wall 51, the magnetic domain 52 </ b> A, and the magnetic domain 52 </ b> B is performed inside the domain wall moving layer 111. The initialization method may be any method as long as the domain wall 51 can be formed in the domain wall moving layer 111. For example, the initialization can be performed by the following method.

  First, by applying an external magnetic field larger than the coercive force of the domain wall motion layer 111, the magnetization direction of the domain wall motion layer 111 is made uniform. Subsequently, a part of the domain wall motion layer 111 is heated by the heating unit 12A or the heating unit 12B, and an external magnetic field opposite to the above external magnetic field is applied in a state where the coercive force of the heated heating region is reduced. Only the magnetization of the heating region is reversed. The magnitude of the external magnetic field applied at this time is set to be larger than the coercive force of the heated region and smaller than the coercive force of the unheated region. In this way, the domain wall 51 can be formed inside the domain wall moving layer 111.

  Here, the lower electrode 115 may be a conductive substrate, or a through hole may be formed in a substrate (not shown) to be connected to the power source from the surface side of the lower electrode with respect to the substrate. It may be formed with a larger area than the stacked body from the moving layer 111 to the fixed layer 113 and connected to the power source from the surface side of the lower electrode 115 with respect to the fixed layer 113.

  3A to 3E show the method of forming the magnetic memory 1 in the first embodiment on the substrate in order from the lower electrode 115 side, the substrate is not shown in order from the upper electrode 114 side. You may use the manufacturing method to form.

  FIG. 4 is a perspective view showing an embodiment in which the magnetic memory according to the first embodiment is used as a memory array. As shown in FIG. 4, the magnetic memory 1 of the present embodiment has a memory by connecting a bit line 61, a word line 62, and a selection transistor 63 for energizing the magnetic memory 1, as in the conventional MRAM. It may be used as an array.

  Further, for the purpose of protecting the domain wall motion layer 111 or the fixed layer 113 and the purpose of amplifying the magnetoresistive effect, each layer between the upper electrode 114 and the domain wall motion layer 111 or from the domain wall motion layer 111 to the lower electrode 115 is used. Between them, a metal layer or a metal multilayer film may be formed regardless of whether it is a magnetic material. For example, a high spin polarizability material typified by CoFeB has a thickness of about 2 nm or less at the interface where the domain wall motion layer 111 and the fixed layer 113 are in contact with the nonmagnetic layer 112 in order to increase the magnetoresistance change effect. It may be formed.

  The magnetic memory 1 in FIG. 1 has a configuration in which two heating units are formed, but three or more heating units may be formed. FIG. 5 is a cross-sectional view showing another configuration example of the magnetic memory according to the first embodiment. The magnetic memory 1A shown in FIG. 5 is different from the magnetic memory 1 in that four heating units are provided and a power supply 13 is provided corresponding to the four heating units. Other configurations are the same. Hereinafter, a method for moving the domain wall 51 in the magnetic memory 1A will be described.

  First, as shown in the figure, when the domain wall 51 is formed at the position of the heating unit 12D, heating is performed by the heating unit in the order of the heating units 12C, 12B, and 12A in the same manner as the magnetic memory 1. The domain wall 51 can be moved to the position of the heating unit 12A.

  On the other hand, when the domain wall 51 exists at the position of the heating unit 12A, conversely, if heating is performed in the order of the heating units 12B, 12C, and 12D, the domain wall 51 can be moved to the position of the heating unit 12D. By doing in this way, the effect which can give a big movement amount with respect to the domain wall 51B, without supplying the electric current of a high current density is acquired.

  Furthermore, if the domain wall 51 is moved and fixed at the position of the heating unit 12B or 12C, the magnetoresistance of the magnetoresistive effect element 11 can be changed in stages, and multi-value recording is possible. A magnetic memory 1A can be provided.

  In the magnetic memory 1 and the magnetic memory 1A, one domain wall is formed. However, in the magnetic memory according to the present embodiment, it is sufficient that at least one domain wall is formed, and a plurality of domain walls are formed. It may be. A magnetic memory having a plurality of domain walls will be described below.

  FIG. 6 is a sectional view showing another configuration example of the magnetic memory according to the first embodiment. The magnetic memory 1B shown in FIG. 5A is different from the magnetic memory 1 of FIG. 1 in that three domain walls 51A to 51C are formed. Further, since three domain walls are formed, four magnetic domains 52A to 52D are formed accordingly. Other configurations are the same as those of the magnetic memory 1.

  In the magnetic memory 1B, the domain wall moving layer 111 is heated by the heating units 12A and 12B, thereby moving each of the domain walls 51A to 51C toward the heating center, and the areas of the magnetic domains 52A to 52D in the domain wall moving layer 111. The ratio can be changed. Specifically, the domain walls 51A to 51C can be moved from the position shown in FIG. 6A to the position shown in FIG. 6B by heating the heating unit 12A. On the other hand, the domain walls 51A to 51C can be moved from the position shown in FIG. 6B to the position shown in FIG. Thereby, the magnetoresistive effect can be obtained similarly to the magnetic memory 1.

  FIG. 7 is a cross-sectional view showing still another configuration example of the magnetic memory 1. As shown in FIG. 7, the magnetic memory 1 </ b> C is similar to the magnetic memory 1 </ b> B in that two heating units 12 </ b> A and 12 </ b> B and three domain walls 51 </ b> A to 51 </ b> C are formed. However, it differs from the magnetic memory 1B in that the domain wall 51A and the domain wall 51C are formed outside the range that can be heated by the heating unit 12A and the heating unit 12B.

  In the magnetic memory 1C, when the domain wall moving layer 111 is heated by the heating unit 12A and the heating unit 12B, the domain wall 51B moves, but the domain wall 51A and domain wall 51C do not move, and the domain 52C and domain 52D change the area. Absent. Therefore, since the domain walls 51A and 51C are not involved in the change of the magnetic resistance, they are not originally required to be formed in the domain wall moving layer 111. However, it is conceivable that the domain walls 51A and 51C that are not involved in the change in the magnetic resistance are formed by some external factor, for example, when a strong magnetic field is applied from the outside. Even in such a case, in the magnetic memory 1C, the area ratio of the magnetic domains 52A and 52B having opposite magnetizations is changed by the movement of the domain wall 51B. Can be obtained.

  Thus, even when there are two or more domain walls 51 as shown in FIGS. 6 and 7, the magnetic memory 1 according to the present embodiment can be realized.

  Further, in the magnetic memory according to the present embodiment, three or more heating units and a plurality of domain walls may be formed. FIG. 8 is a sectional view showing still another configuration example of the magnetic memory 1 according to the first embodiment. In the magnetic memory 1D, four heating units 12A to 12D and two domain walls 51A and 51B are formed. Thus, after forming the two domain walls 51A and the domain wall 51B, the plurality of heating units among the four heating units 12A to 12D are simultaneously used to move the domain wall 51A and the domain wall 51B at the same time. A magnetic memory 1D capable of recording multiple values at high speed without passing a current having a current density can be realized.

  For example, the domain wall 51A and the domain wall 51B are formed, and the domain wall 51A is moved between the heating unit 12A and the heating unit 12B. On the other hand, the domain wall 51B is moved between the heating parts 12C and 12D. In this way, since the moving distance of each domain wall 51A or B can be reduced, a magnetic memory 1D capable of rewriting information at higher speed can be realized.

[Embodiment 2]
The following will describe another embodiment according to the present invention with reference to FIG. Configurations other than those described in the second embodiment are the same as those in the first embodiment. For convenience of explanation, members having the same functions as those shown in the drawings of Embodiment 1 described above are given the same reference numerals, and descriptions thereof are omitted.

  In the magnetic memory 2 according to the second embodiment, compared to the configuration of the magnetic memory 1 according to the first embodiment, the length in the moving direction of the domain wall 51 of the domain wall moving layer 111 is different from that of the nonmagnetic layer 112 and the fixed layer. The difference is that the layer 113 is formed longer than the layer 113. Other configurations are the same as those of the magnetic memory 1 according to the first embodiment.

  FIG. 9 is a cross-sectional view showing the magnetic memory 2 of the second embodiment. As shown in FIG. 9, the magnetic memory 2 according to the second embodiment has a length of the domain wall moving layer 111, that is, a domain wall in the direction in which the domain wall 51 moves, in a direction orthogonal to the plane of the domain wall 51 (the horizontal direction in the drawing). The length of the moving layer 111 is longer than the length of the portion where the domain wall moving layer 111 and the nonmagnetic layer 112 are in contact with each other.

  The heating center of the heating unit 12A and the heating unit 12B is formed on the domain wall moving layer 111 and outside the region where the domain wall moving layer 111 and the nonmagnetic layer 112 overlap. The region where the domain wall motion layer 111 and the nonmagnetic material layer 112 are overlapped is the surface of the domain wall motion layer 111 where the domain wall motion layer 111 and the nonmagnetic material layer 112 are in contact with each other, and the reverse of the contact surface in the domain wall motion layer 111. The area | region containing the area | region facing the said contact surface among surfaces is shown. The other members and the recording / reproducing method are the same as those in the first embodiment.

  In the magnetic memory 2 according to the present embodiment, the length of the domain wall motion layer 111 is longer than the length of the nonmagnetic material layer 112, and the heating centers of the heating unit 12A and the heating unit 12B are the nonmagnetic material layer 112. And the domain wall motion layer 111 are formed outside the region where the magnetic wall motion layer 111 overlaps, the domain wall motion layer 111 is locally heated by the heating unit 12A or the heating unit 12B, and the domain wall 51 toward the center of the temperature rise region is The nonmagnetic material layer 112 and the domain wall motion layer 111 can be moved outside the region where they overlap.

  Therefore, when the magnetoresistive effect is detected by energizing between the upper electrode 114 and the lower electrode 115, the inner region of the domain wall motion layer 111 on the surface where the domain wall motion layer 111 and the nonmagnetic material layer 112 are in contact with each other is detected. The domain wall 51 does not exist. Therefore, when detecting the magnetoresistive effect, the magnetization direction of the region of the domain wall motion layer 111 that contributes to the change of the magnetic resistance, that is, the inner region of the domain wall motion layer 111 in the plane in contact with the nonmagnetic layer 112. Can be unidirectional. Thereby, a larger magnetoresistance effect than that of the magnetic memory 1 shown in the first embodiment can be obtained.

  Furthermore, in the magnetic memory 2, since the fixed layer 113 does not exist immediately below the heating centers of the heating unit 12A and the heating unit 12B, an effect of preventing the fixed layer 113 from being heated excessively and becoming unable to fix the magnetization can be obtained.

  In the manufacture of the magnetic memory 2 according to the second embodiment, once the process from the lower electrode 115 to the nonmagnetic material layer 112 is formed in the process shown in FIGS. The magnetic memory 2 can be manufactured by performing processing using a lithography method or the like and subsequently forming the domain wall motion layer 111 and the subsequent layers. At this time, since the magnetization state of the interface sandwiching the nonmagnetic layer 112 particularly affects the magnetoresistive effect, after the nonmagnetic layer 112 is formed, a part of the domain wall motion layer 111 is formed, and thereafter The remaining domain wall motion layer 111 may be formed. Alternatively, the upper electrode 114 may be formed first on a substrate (not shown), and the domain wall motion layer 111 to the fixed layer 113 may be continuously formed to perform the lithography process.

  In the magnetic memory 2 of the second embodiment, as shown in FIG. 9, the heating unit 12A and the heating unit 12B are not necessarily formed on the upper side of the domain wall motion layer 111 (opposite side of the nonmagnetic layer 112). Alternatively, it may be formed below the domain wall motion layer 111 (on the same side as the nonmagnetic layer 112).

  Also, in the magnetic memory 2 of the second embodiment, as in the first embodiment, three or more heating parts for heating the domain wall motion layer 111 may be formed. . As a result, it is possible to obtain an effect that a large domain wall motion can be obtained without passing a current having a high current density, and it is possible to change the magnetoresistance of the magnetoresistive effect element 11 step by step. A magnetic memory 1 capable of recording a value can be provided.

  Furthermore, two or more domain walls 51 may exist in the domain wall moving layer 111. Specifically, for example, in the magnetic memory 1 as shown in FIG. 6 to FIG. 8, the length in the direction perpendicular to the surface of the domain wall 51 of the domain wall moving layer 111 (the horizontal direction in the drawing) as in the second embodiment. Is longer than the length of the portion where the domain wall motion layer 111 and the nonmagnetic material layer 112 are in contact, and the heating center of the heating parts 12A and 12B is larger than the region where the nonmagnetic material layer 112 and the domain wall motion layer 111 are in contact with each other. It may be formed outside.

[Embodiment 3]
The following will describe still another embodiment of the present invention with reference to FIG. Configurations other than those described in the third embodiment are the same as those in the first and second embodiments described above. For convenience of explanation, members having the same functions as those shown in the drawings of Embodiments 1 and 2 described above will be given the same reference numerals and explanation thereof will be omitted.

  A third embodiment of the present invention will be described below. In the magnetic memory 3 according to the third embodiment, the domain wall motion layer 111 is formed in a thin line shape as compared with the configuration of the magnetic memories 1 and 2 of the first and second embodiments described above, and the domain wall motion layer is externally provided. It differs from the magnetic memory shown in Embodiments 1 and 2 in that the entire domain wall of the domain wall moving layer 111 is moved by passing a current through 111.

  FIG. 10 is a cross-sectional view showing an embodiment of the magnetic memory 3 according to the third embodiment. As shown in FIG. 10, a magnetic memory 3 according to the third embodiment is obtained by applying the magnetic memory 1 shown in the first and second embodiments to a thin-line magnetic memory.

  That is, in the magnetic memory 3, the upper electrode 114, the domain wall motion layer 111, the nonmagnetic material layer 112, the fixed layer 113, and the lower electrode 115 are laminated. A domain wall 51 is formed in the domain wall moving layer 111 similarly to the magnetic memory 1, but a plurality of domain walls 51 are formed and a plurality of magnetic domains are also formed. The domain wall motion layer 111 is set to have a longer length along the magnetization direction than the nonmagnetic layer 112 and the fixed layer 113, and the magnetic memory 3 has a U-shape. However, the shape is not particularly limited. Unlike the magnetic memory 1, the heating unit 12 is formed on the same surface as the nonmagnetic layer 112 of the domain wall motion layer 111. Of course, as with the magnetic memory 1, it may be formed on the surface of the domain wall motion layer 111 opposite to the non-magnetic layer 112.

  A power source 13 is connected to the heating unit 12, and a current 14 is applied to both ends of the domain wall moving layer 111 by energizing means (not shown). An example of the energization means is an electronic circuit.

  Next, a method for rewriting magnetic recording information using the magnetic memory 3 will be described. First, by causing the current 14 to flow through the domain wall motion layer 111, a spin polarization of the current corresponding to the spin direction of the magnetic material is generated. When this spin-polarized current flows through the domain wall motion layer 111, a magnetic torque is generated for the magnetic substance spin in the domain wall motion layer 111. With this magnetic torque, the entire domain wall of the domain wall moving layer 111, that is, the entire domain including the domain 52 to be rewritten can be moved to an arbitrary position. In order to move the entire magnetic domain 52 to a desired position, the domain wall moving layer 111 may be energized by controlling the intensity of the current 14 and the pulse width.

  In this way, after the magnetic domain 52 to be rewritten is moved to the heating unit 12, the domain wall moving layer 111 is locally heated by the heating unit 12, whereby the domain wall 51 included in the heated temperature rise region. To record magnetic information. In the third embodiment, since the entire magnetic domain can be moved by the current 14, at least one heating unit 12 may be provided.

  As described above, according to the magnetic memory 3, the whole of the plurality of domain walls can be moved by the current in the domain wall moving layer. Therefore, the domain wall at a desired position can be provided even if the number of heating units is as small as one. 51 can be moved individually and with a desired width.

  The magnetic information recording mechanism in the magnetic memory 3 according to the third embodiment is the same as that of the magnetic memories 1 and 2 described in the first and second embodiments. That is, when the domain wall moving layer 111 is locally heated so that the domain wall 51 is included by the heating unit 12, the domain wall 51 receives the domain wall driving force and the leakage magnetic field from the magnetic domain 52 adjacent to the domain wall 51 toward the heating center. Moving. Thereby, the length of the magnetic domain 52 in the domain wall motion layer 111 can be changed. If the front end and the rear end of the magnetic domain 52 are moved in the same length and in the same direction, the position can be shifted without changing the length of the magnetic domain 52. Thus, the magnetic information in the magnetic memory 2 is recorded by a combination of the orientation and length (interval) of the magnetic domains 52.

  The recorded information is read by moving the entire magnetic domain by passing the current 14, thereby moving the magnetic domain 52 to be read onto the magnetoresistive effect element 11 (on the nonmagnetic layer 112), and the upper electrode 114. A current for detecting the magnetoresistive effect is passed between the first electrode 115 and the lower electrode 115.

  Similarly to the magnetic memories 1 and 2 in the first or second embodiment described above, the magnetic memory 3 of the third embodiment also includes a plurality of domain walls 51 (magnetic domains) having magnetization directions opposite to each other in the domain wall moving layer 111. 52) is formed. Any method may be used for the initialization process as long as it can form a plurality of magnetic domains 52 having opposite magnetizations in the domain wall motion layer 111. Specifically, for example, Can be done.

  That is, as in the first and second embodiments, first, by applying an external magnetic field larger than the coercive force of the domain wall motion layer 111, the magnetization direction of the domain wall motion layer 111 is made uniform. Subsequently, in a state where a part of the domain wall moving layer 111 is heated by the heating unit 12 and the coercive force of the heating region is reduced, an external magnetic field in the opposite direction to the above external magnetic field is applied to only magnetize the heating region. Invert. The magnitude of the external magnetic field applied at this time is set to be larger than the coercive force of the heated region and smaller than the coercive force of the unheated region.

  In this manner, the domain wall 51 (domain 52) can be formed inside the domain wall moving layer 111. In addition, it is possible to form the domain wall 51 by utilizing the bending of the domain wall moving layer 111. Specifically, an external magnetic field larger than the coercive force of the domain wall moving layer 111 is applied in the direction orthogonal to the domain wall 51 (the left and right direction in the drawing) and the thickness direction of the domain wall moving layer 111 (the vertical direction in the drawing). The magnetic wall 51 may be formed in the bent portion by applying a magnetic field in an oblique direction corresponding to the above to the domain wall moving layer 111.

  In the magnetic memory 3 of the third embodiment, the magnetoresistive effect element 11 forms the upper electrode 114 as shown in FIG. 7, and detects the magnetoresistive effect by energizing between the upper electrode 114 and the lower electrode 115. The upper electrode 114 may not be formed, and the magnetoresistive effect may be detected by energizing between the domain wall motion layer 111 and the lower electrode 115.

  Also in the magnetic memory 3 according to the third embodiment, the heating unit 12 does not have to be a resistance heating element that generates Joule heat, and may be the heating unit 12 that is heated by light irradiation. Also, a plurality of heating units 12 may be formed.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the technical means disclosed in different embodiments can be appropriately combined. Such embodiments are also included in the technical scope of the present invention.

[Example 1]
In the magnetic memories 1 and 2 shown in the first and second embodiments, the domain wall motion layer 111 is made of GdFeCo having a Curie temperature of 330 ° C. and a TM-rich composition as the in-plane magnetization film, and MgO is used for the nonmagnetic layer 112. For the fixed layer 113, a structure using a laminated film of CoFeB and MnPt having a blocking temperature of 360 ° C. was adopted.

First, a heating condition necessary for moving the domain wall 51 inside the domain wall moving layer 111 was obtained by calculation. The temperature distribution of the domain wall moving layer 111 during heating assumes a Gaussian distribution, and the temperature rise range (the range in which the temperature rise is 1 / e ² ) in the direction orthogonal to the domain wall 51 (the horizontal direction in FIG. 1) is It was 1 μm. The saturation magnetization Ms of GdFeCo at room temperature was 210 emu / cc, the uniaxial anisotropy constant Ku was 1.4 × 10 ⁵ erg / cc, and the exchange stiffness constant A was 5 × 10 ⁻⁷ erg / cm.

FIG. 11 is a graph showing the domain wall driving force (converted to the magnetic field) generated by the temperature gradient accompanying heating and applied to the domain wall 51 with respect to the temperature at the heating center (the temperature at the highest temperature position). In calculating the domain wall driving force, GdFeCo used in Example 1 has a TM-rich composition and a composition far from the compensation temperature to the extent that it exhibits in-plane magnetization. Therefore, Ms, Ku and It approximated that A changed linearly in the range from room temperature to the Curie temperature. The domain wall energy σ was determined from 4 × (A · Ku) ^0.5 .

  The domain wall driving force (magnetic field conversion) on the vertical axis is calculated from (∂σ / ∂x) · (1 / 2Ms), and the position (from the center) where the largest driving force is obtained at the tail of the temperature distribution indicated by the Gaussian distribution. Value corresponding to the position of 250 nm). The room temperature was 30 ° C. In addition, the positive direction of the vertical axis | shaft in a figure is corresponded to the direction which moves the domain wall 51 to a heating center direction.

  As shown in FIG. 11, the domain wall driving force (converted to the magnetic field) applied to the domain wall 51 becomes stronger as the temperature rises. For example, when the heating center is heated to 330 ° C., which is the Curie temperature of GdFeCo, it is about 340 Oe. A domain wall driving force corresponding to the magnetic field is obtained. Therefore, when the domain wall 51 is at a position 250 nm from the heating center, if the coercive force of the domain wall moving layer 111 (coercivity at a position 250 nm from the center) is at least 340 Oe or less, the domain wall 51 is obtained only by the domain wall driving force. Can move toward the center of heating. Here, since the temperature rise at the position of 250 nm from the heating center is about 60% of the heating center, if the coercive force of GdFeCo is at least 340 Oe or less at a temperature of about 200 ° C., the domain wall motion is Will happen. This value can be easily realized by using GdFeCo.

  In addition to the domain wall driving force, in the magnetic memories 1 and 2, the domain wall moving layer 111 is an in-plane magnetization film, and the magnetization directions of the magnetic domains 52A and 52B are perpendicular to the domain wall 51. The leakage magnetic field applied to the heating region from 52A and 52B gives a force in a direction to assist the domain wall movement (dipole interaction). For example, when the domain wall moving layer 111 has a thickness (up and down direction in the drawing) of 30 nm, a width (in the depth direction of the drawing) of 250 nm, and the magnetic domains 52A and 52B outside the temperature rise range each having a length of 500 nm, A magnetic field of about 70 Oe is applied to the domain wall 51 from the magnetic domain outside the temperature rise range in the same direction as the domain wall driving force.

  As described above, in the magnetic memories 1 and 2, the domain wall driving force is generated in the domain wall 51 by heating, and the coercive force of the domain wall moving layer 111 is smaller than the sum of the domain wall driving force and the leakage magnetic field from the magnetic domains 52A and 52B. By heating the domain wall moving layer 111, the domain wall 51 can be moved toward the center of heating. Thereby, the area ratio of the magnetic domains 52A and 52B facing each other with the domain wall 51 interposed therebetween is changed, and the magnetic resistance can be changed.

  Furthermore, in the magnetic memory 2 shown in the second embodiment, in addition to this, only a unidirectional magnetic domain exists at the interface contributing to the magnetoresistive effect, so that a larger magnetoresistive effect can be obtained.

[Example 2]
As Example 2, an example using NiFe instead of GdFeCo used for the domain wall motion layer 111 in Example 1 described above will be described. Here, the Curie temperature of NiFe is 400 ° C., the saturation magnetization Ms is 800 emu / cc, the uniaxial anisotropy constant Ku is 1 × 10 ³ erg / cc, and the exchange stiffness constant A is 1.05 × 10 ⁻⁶ erg / cm. The other conditions were the same as in Example 1.

  In FIG. 12, similarly to FIG. 11, the domain wall driving force (magnetic field conversion) applied to the domain wall 51 during heating by the heating unit 12A or 12B is shown with respect to the heating temperature (heating center temperature). As shown in FIG. 12, the domain wall driving force (converted to the magnetic field) applied to the domain wall 51 becomes stronger as the temperature rises, and when the heating center is heated to 400 ° C., which is the Curie temperature of NiFe, A domain wall driving force corresponding to a magnetic field exceeding 10 Oe is applied. Here, considering that the coercive force Hc of NiFe at room temperature is about 2.5 Oe and the coercive force decreases toward the Curie temperature, it is heated up to about 200 ° C. on the graph of FIG. Then, the domain wall driving force exceeds the coercive force, and the domain wall 51 of the domain wall moving layer 111 can be moved toward the heating center only by the domain wall driving force.

  In addition to the domain wall driving force described above, also in the present embodiment, the leakage magnetic field applied from the magnetic domain 52A and the magnetic domain 52B to the heating region gives a force in a direction assisting the domain wall movement (dipole interaction). For example, when the thickness (in the drawing vertical direction) of the domain wall moving layer 111 is 15 nm, the width (in the drawing depth direction) is 250 nm, and the magnetic domains 52A and 52B outside the temperature rise range are each 500 nm long, A magnetic field of about 120 Oe is applied to the domain wall 51 from the magnetic domain outside the temperature rise range in the same direction as the domain wall driving force.

Example 3
In the magnetic memory 3 shown in the third embodiment, similarly to the first embodiment, GdFeCo having a Curie temperature of 330 ° C. and TM-rich composition as the domain wall moving layer 111 and a TM-rich composition is used as the nonmagnetic layer 112. A case in which MgO is used and a laminated film of CoFeB and MnPt having a blocking temperature of 360 ° C. is used for the fixed layer 113 will be described.

Also in the magnetic memory 3 of the third embodiment, as in the first embodiment, the driving force is applied to the domain wall 51 due to the temperature gradient generated by the heating by the heating unit 12, and the domain wall 51 moves. Similarly, when the temperature rise range during heating (range of 1 / e ² ) is calculated as 1 μm, for example, when heated to 330 ° C. which is the Curie temperature of GdFeCo, it is about 340 Oe at a position of 250 nm from the heating center. A domain wall driving force corresponding to a magnetic field is applied. Therefore, if the coercive force (coercive force at a position 250 nm from the center) of the domain wall moving layer 111 in the heating region is at least 340 Oe or less, the domain wall 51 can move toward the heating center only by the domain wall driving force. It becomes possible. That is, the magnetic information can be rewritten in the magnetic memory 2 of the third embodiment.

  Here, in the magnetic memory 3 according to the third embodiment, the current 14 for moving the entire magnetic domain flows to the domain wall moving layer 111, so that the energization and the recording using the heating unit 12 are performed simultaneously, or When performing continuously at high speed, it is desirable to consider the temperature rise of the domain wall motion layer 111 accompanying the current 14.

  In FIG. 13, assuming that the temperature of the domain wall moving layer 111 is increased by the current 14, the temperature of the heating region and the domain wall driving force are converted into magnetic fields (に σ / ∂x for several temperature conditions). ) · (1 / 2Ms). In FIG. 13, (a) is a graph when there is no temperature rise due to current application, (b) is a graph when the temperature rises by 50 ° C., and (c) is a graph when the temperature rises by 100 ° C. From the results shown in FIG. 13, even when the domain wall motion layer 111 rises by 100 ° C. due to the current 14, the temperature associated with passing the current 14 when heated to about 330 ° C., which is the Curie temperature of GdFeCo. When there is no increase, a domain wall driving force (converted to a magnetic field) comparable to that shown in FIG.

  As described above, in the magnetic memory 3 according to the third embodiment, the domain wall driving force is generated in the domain wall 51 by heating, and the coercive force of the domain wall moving layer 111 is the domain wall driving force and the leakage magnetic field from the magnetic domain 52 (dipole interaction). The domain wall 51 can be moved toward the center of heating by heating the domain wall moving layer 111 to be smaller than the sum of. As a result, the length of the magnetic domains facing each other across the domain wall 51 changes, and magnetic information can be recorded. Furthermore, even when local heating is performed by the heating unit 12 simultaneously with the current 14, a driving force sufficient to move the domain wall 51 is obtained.

  According to the present invention, it is possible to provide a magnetic memory capable of using a high coercive force material in a portion for holding magnetic information without passing a current having a high current density through the magnetoresistive effect element.

It is sectional drawing which shows one form of the magnetic memory which concerns on this Embodiment. It is sectional drawing which shows the domain wall moving layer which concerns on this Embodiment. It is sectional drawing which shows the manufacturing process of the magnetic memory which concerns on this Embodiment. It is a perspective view which shows one form in the case of using the magnetic memory which concerns on this Embodiment as a memory array. It is sectional drawing which shows the other structural example of the magnetic memory which concerns on this Embodiment. It is sectional drawing which shows the other structural example of the magnetic memory which concerns on this Embodiment. It is sectional drawing which shows the other structural example of the magnetic memory which concerns on this Embodiment. It is sectional drawing which shows the other structural example of the magnetic memory which concerns on this Embodiment. It is sectional drawing which shows one form of the magnetic memory which concerns on other embodiment in this invention. It is sectional drawing which shows one form of the magnetic memory which concerns on other embodiment in this invention. 3 is a graph showing the relationship between domain wall driving force and temperature in the magnetic memory of Example 1; 6 is a graph showing the relationship between domain wall driving force and temperature in the magnetic memory of Example 2. 6 is a graph showing the relationship between domain wall driving force and temperature in the magnetic memory of Example 3. 10 is a cross-sectional view showing a magnetic information recording method described in Patent Document 1.

Explanation of symbols

1 · 1A · 1B · 1C · 1D · 2 · 3 Magnetic memory 11 Magnetoresistive element 12 · 12A · 12B · 12C · 12D Heating part 13 Power supply 14 Current (energization means)
51, 51A, 51B, 51C Domain wall 52, 52A, 52B, 52D, 52D Domain 61 Bit line 62 Word line 63 Selection transistor 111 Domain wall moving layer 112 Non-magnetic layer 113 Fixed layer 114 Upper electrode 115 Lower electrode 116 Insulator protection film

Claims (7)

A magnetoresistive effect element in which a domain wall motion layer, a nonmagnetic material layer as an intermediate layer, and a fixed layer are laminated, and a heating unit capable of locally heating the domain wall motion layer,
In the domain wall motion layer, the easy axis of magnetization is located in the in-plane direction of the domain wall motion layer,
A domain wall is formed in the domain wall moving layer,
A magnetic memory characterized in that the domain wall moves in the domain wall motion layer by locally heating the domain wall motion layer by the heating unit.   The magnetic memory according to claim 1, wherein a plurality of the heating units are provided. When the direction perpendicular to the domain wall is the length direction, the length of the domain wall motion layer is longer than the length of the nonmagnetic layer,
3. The magnetic memory according to claim 1, wherein a center position of the heating unit in a length direction is formed outside a region where the domain wall motion layer and the nonmagnetic material layer overlap each other. A plurality of the domain walls are formed,
The magnetic memory according to any one of claims 1 to 3, wherein energizing means for moving the whole of the plurality of domain walls in the domain wall moving layer is connected to the domain wall moving layer.   5. The magnetic memory according to claim 1, wherein the heating unit generates heat by generating Joule heat to locally heat the domain wall moving layer. 6.   5. The magnetic memory according to claim 1, wherein the heating unit generates heat when irradiated with light to locally heat the domain wall motion layer. 6.   The magnetic memory according to claim 1, wherein the magnetic wall moving layer is locally heated by the heating unit, and the magnetic wall is moved in the magnetic wall moving layer. Information recording method in magnetic memory.

Images