JP2011205007A - Magnetic memory, and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for allowing writing with a lower writing current, in a magnetic memory including memory cells for performing writing by using current-induced domain wall displacement.SOLUTION: Each memory cell 80 of this magnetic memory includes: a first base layer 41 formed of any of Ti, Zr, Nb, Mo, Hf, Ta and W, or two or more materials selected from a group of them; a second base layer 42 formed on the first base layer 41 and formed of any of Cu, Rh, Pd, Ag, Ir, Pt and Au, or two or more materials selected from a group of them; and a domain wall displacement layer 10 formed on the second base layer 42 and having vertical magnetic anisotropy. The domain wall displacement layer 10 includes a free magnetic region 13 having an invertible magnetization direction, and the magnetization direction of the free magnetic region 13 is inverted by current-induced domain wall displacement by carrying writing current to the free magnetic region 13. The film thickness of the second base layer is ≤0.9 nm.

Description

  The present invention relates to a magnetic memory and a method for manufacturing the same, and more particularly to a magnetic memory having a domain wall moving layer having perpendicular magnetic anisotropy, and having a memory cell that performs writing using current induced domain wall movement in the domain wall moving layer. And a manufacturing method thereof.

  A magnetic memory, in particular, a magnetic random access memory (MRAM), is a non-volatile memory capable of high-speed operation and infinite rewriting. For this reason, practical use of MRAM has started in part, and development for further enhancing versatility is being carried out. The MRAM uses a magnetic material as a storage element and stores data corresponding to the magnetization direction of the magnetic material. In order to write desired data to the storage element, the magnetization of the magnetic material is switched to a direction corresponding to the data. Several methods have been proposed as switching methods of the magnetization direction, all of which are common in that a current (hereinafter referred to as “write current”) is used. In practical use of MRAM, it is very important how much the write current can be reduced.

Non-Patent Document 1 (N.Sakimura
et al., “MRAM Cell Technology for Over 500-MHz SoC”, IEEE JOURNAL OF SOLID-STATE
According to CIRCUITS, VOL.42, NO.4, pp.830-838, 2007.) By reducing the write current to 0.5 mA or less, the cell area is equivalent to that of the existing embedded SRAM. ing.

  The most common method of writing data to the MRAM is to arrange a wiring for writing around the magnetic memory element and generate a magnetic field by flowing a write current through the wiring, and the magnetic field of the magnetic memory element is generated by the magnetic field. This is a method of switching the magnetization direction. According to this method, writing in 1 nanosecond or less is possible in principle, which is suitable for realizing a high-speed MRAM. However, the magnetic field for switching the magnetization of the magnetic material that has ensured thermal stability and disturbance magnetic field resistance is generally about several tens of Oe (Yersted). In order to generate such a magnetic field, several A write current of about mA is required. In this case, the chip area must be increased, and the power consumption required for writing also increases, so that it is inferior in competitiveness compared to other random access memories. In addition to this, when the element is miniaturized, the write current further increases, which is not preferable in terms of scaling.

  In recent years, the following two methods have been proposed as means for solving such problems.

  The first is a spin torque transfer system. According to the spin injection magnetization reversal method, the second magnetic layer is composed of a first magnetic layer having reversible magnetization and a second magnetic layer that is electrically connected thereto and whose magnetization direction is fixed. A write current is passed between the magnetic layer and the first magnetic layer. At this time, the magnetization of the first magnetic layer can be reversed by the interaction between the spin-polarized conduction electrons and the localized electrons in the first magnetic layer. At the time of reading, a magnetoresistive effect developed between the first magnetic layer and the second magnetic layer is used. Therefore, a magnetic memory element using spin injection magnetization reversal is a two-terminal element. Since spin transfer magnetization reversal occurs at a certain current density or higher, the current required for writing is reduced if the element size is reduced. That is, it can be said that the spin injection magnetization reversal method is excellent in scaling. However, generally, an insulating layer is provided between the first magnetic layer and the second magnetic layer, and a relatively large write current must be passed through the insulating layer during writing. Rewriting durability and reliability are issues. Further, since the write current path and the read current path are the same, there is a concern about erroneous writing during reading. Thus, although spin transfer magnetization reversal is excellent in scaling, there are some barriers to practical use.

The second is a current-driven domain wall motion system. An MRAM using current-induced domain wall motion is disclosed in, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2005-191032). In a general current-induced domain wall motion type MRAM, a magnetic layer having reversible magnetization (domain wall motion layer for storing data) is provided, and the magnetizations at both ends of the domain wall motion layer are substantially antiparallel to each other. Fixed to. With such a magnetization arrangement, the domain wall is introduced into the domain wall moving layer. Here, Non-Patent Document 2 (A. Yamaguchi et al., “Real-Space Observation of Current-Driven Domain
Wall Motion in Submicron Magnetic Wires ”, PHYSICAL REVIEW
As reported in LETTERS, VOL.92, NO.7,077205, 2004.), when a current is passed through the domain wall, the domain wall moves in the direction of conduction electrons. Therefore, by supplying a write current in the in-plane direction to the domain wall moving layer, it is possible to move the domain wall in a direction corresponding to the current direction and write desired data. At the time of reading, a magnetic tunnel junction including a region where the domain wall moves is used, and reading is performed based on the magnetoresistance effect. Therefore, a magnetic memory element using current-induced domain wall motion is a three-terminal element. Similarly to spin injection magnetization reversal, current induced domain wall motion also occurs when the current density is greater than a certain current density. Therefore, it can be said that the current induced domain wall motion method is also excellent in scaling. In addition, in the case of the current-induced domain wall motion method, the write current does not flow through the insulating layer, and the write current path and the read current path are different. Therefore, the above-mentioned problem in the case of spin injection magnetization reversal is solved.

In Non-Patent Document 2 described above, a current density of about 1 × 10 ⁸ [A / cm ² ] is reported as a current density necessary for current-induced domain wall motion.

Non-Patent Document 3 (S.Fukami
et al., “Micromagnetic analysis of current driven domain wall motion in
nanostrips with perpendicular magnetic anisotropy ”, JOURNAL OF APPLIED
PHYSICS, VOL.103, 07E718, 2008.) describes the usefulness of perpendicular magnetic anisotropic materials in current-induced domain wall motion. Specifically, it has been found through micromagnetic simulation that the write current can be reduced sufficiently small when the domain wall motion layer where domain wall motion occurs has perpendicular magnetic anisotropy.

  Patent Document 2 (International Publication WO / 2009/001706) discloses a magnetoresistive effect element using a magnetic material having perpendicular magnetic anisotropy, and an MRAM including the magnetoresistive element as a memory cell. FIG. 1 is a cross-sectional view schematically showing a magnetoresistive effect element disclosed in Patent Document 2. As shown in FIG. The magnetoresistive effect element 170 includes a domain wall motion layer 110, a spacer layer 120, and a reference layer 130.

  The domain wall motion layer 110 is formed of a ferromagnetic material having perpendicular magnetic anisotropy. The domain wall motion layer 110 includes a first magnetization fixed region 111a, a second magnetization fixed region 111b, and a magnetization free region 113. The magnetization fixed regions 111 a and 111 b are arranged on both sides of the magnetization free region 113. The magnetizations of the magnetization fixed regions 111a and 111b are fixed in opposite directions (antiparallel). For example, as shown in FIG. 1, the magnetization direction of the first magnetization fixed region 111a is fixed in the + z direction, and the magnetization direction of the second magnetization fixed region 111b is fixed in the -z direction. On the other hand, the magnetization direction of the magnetization free region 113 can be reversed by a write current flowing from one of the magnetization fixed regions 111a and 111b to the other, and becomes the + z direction or the −z direction. Therefore, the domain wall 112 a or the domain wall 112 b is formed in the domain wall moving layer 110 according to the magnetization direction of the magnetization free region 113. Data is stored as the magnetization direction of the magnetization free region 113. It can also be seen that it is stored as the position (112a or 112b) of the domain wall 112. The reference layer 130, which is a ferromagnetic material whose magnetization direction is fixed, the spacer layer 120 of the nonmagnetic layer (insulating layer), and the magnetization free region 113 form a magnetic tunnel junction (MTJ). The data is read as the magnitude of the MTJ resistance value.

  Patent Document 2 discloses that when the domain wall motion layer 110 has perpendicular magnetic anisotropy, the write current can be reduced.

  A similar technique is disclosed in Patent Document 3 (Japanese Patent Laid-Open No. 2009-252909). This publication mentions the material of the ferromagnetic layer in which the domain wall moves, and discloses that the ferromagnetic layer is a laminated film of Co / Pd, Co / Pt, Co / Ni, and Fe / Au. Yes.

  When forming a magnetic layer having perpendicular magnetic anisotropy, an underlayer may be provided. For example, Patent Document 4 (Japanese Patent Laid-Open No. 2008-135676) discloses a Ta layer as a base layer of a magnetic layer having a laminated structure composed of CoFeSiB and Pt and having perpendicular magnetic anisotropy, The use of a formed Pt layer is disclosed. A technique using two underlayers for a GMR element is disclosed in Patent Document 5 (Japanese Patent Laid-Open No. 11-87802).

JP 2005-191032 A International Publication WO2009 / 001706 Pamphlet JP 2009-252909 A JP 2008-135676 A Japanese Patent Laid-Open No. 11-87802

N. Sakimura et al., “MRAM Cell Technology for Over 500-MHz SoC”, IEEE JOURNAL OF SOLID-STATECIRCUITS, VOL.42, NO.4, pp.830-838, (2007). A. Yamaguchi et al., “Real-Space Observation of Current-Driven Domain Wall Motion in Submicron Magnetic Wires”, PHYSICAL REVIEW LETTERS, VOL.92, NO.7,077205, (2004). S. Fukamiet al., “Micromagnetic analysis of current driven domain wall motion innanostrips with perpendicular magnetic anisotropy”, JOURNAL OF APPLIEDPHYSICS, VOL.103, 07E718, (2008). A. Thiaville et al., “Domain wall motion by spin-polarized current: amicromagnetic study”, JOURNAL OF APPLIED PHYSICS, VOL. 95, NO. 11, pp. 7049-7051, (2004). G.H.O.Dalalderopet al., “Prediction and Confirmation of Perpendicular Magnetic Anisotropy inCo / Ni Multilayers”, PHYSICAL REVIEW LETTERS, VOL.68, NO.5, pp.682-685, (1992). T. Suzuki et al., “Evaluation of Scalability for Current-Driven Domain Wall Motion in aCo / Ni Multilayer Strip for Memory Applications”, IEEE TRANS ACTIONS ONMAGNETICS, VOL.45, NO.10, pp.3776-3779, (2009) .

  When the domain wall motion layer (domain wall motion layer) has perpendicular magnetic anisotropy as disclosed in Non-Patent Document 3 and Patent Documents 2 and 3 described above, in the domain wall motion layer, It is possible to cause domain wall motion with a smaller write current compared to the method.

  Here, the inventor examined the following points this time. When the domain wall motion layer is formed of a ferromagnetic material having perpendicular magnetic anisotropy, it is considered that the write current can be further reduced if the spin polarizability of the domain wall motion layer can be further increased. Clarification of the relationship between spin polarizability and perpendicular magnetic anisotropy (anisotropic magnetic field) in ferromagnets, and spin by applying the optimum perpendicular magnetic anisotropy (anisotropic magnetic field) to the domain wall moving layer It is considered that the write current can be further reduced by further increasing the polarizability.

  One object of the present invention is to provide a magnetic memory having a domain wall moving layer having perpendicular magnetic anisotropy, and having a memory cell that performs writing using current induced domain wall movement in the domain wall moving layer. It is to provide a technique for making writing possible.

  In one aspect of the invention, a magnetic memory includes memory cells. The memory cell is in contact with the first base layer and a first base layer made of Ti, Zr, Nb, Mo, Hf, Ta, W or two or more materials selected from these groups. A second underlayer made of Cu, Rh, Pd, Ag, Ir, Pt, Au, or two or more materials selected from the group formed on the first underlayer; A domain wall motion layer having perpendicular magnetic anisotropy formed on the second underlayer so as to be in contact with the ground layer. The domain wall motion layer has a magnetization free region whose magnetization direction can be reversed, and the magnetization direction of the magnetization free region is reversed by current induced domain wall motion by flowing a write current through the magnetization free region. The film thickness of the second underlayer is 0.9 nm or less.

  In another aspect of the present invention, a method of manufacturing a magnetic memory includes a first underlayer made of two or more materials selected from Ti, Zr, Nb, Mo, Hf, Ta, and W, or a group thereof. And forming a second underlayer made of Cu, Rh, Pd, Ag, Ir, Pt, Au, or two or more materials selected from these groups on the first underlayer. Forming a domain wall moving layer having a magnetization free region whose magnetization direction can be reversed and having perpendicular magnetic anisotropy on the second underlayer, and a magnetization direction of the magnetization free region Providing an electrode for causing a write current to flow in the magnetization free region. The film thickness of the second underlayer is 0.9 nm or less.

  According to the present invention, it is possible to provide a technique for enabling writing with a lower write current in a magnetic memory having memory cells that perform writing using current-induced domain wall motion.

FIG. 1 is a cross-sectional view schematically showing a conventional magnetoresistive element. FIG. 2 is a schematic cross-sectional view showing the configuration of the magnetoresistive effect element according to the embodiment of the present invention. FIG. 3 is a plan view showing the configuration of the magnetoresistive element of FIG. FIG. 4 is a schematic circuit diagram showing a configuration example of a memory cell for 1 bit according to an embodiment of the present invention. FIG. 5 is a block diagram showing a configuration example of a magnetic memory according to one embodiment of the present invention. FIG. 6 is a graph showing the relationship between the write current required for writing and the Pt film thickness in Example 1 of the present invention. FIG. 7 is a graph showing the relationship between the write current required for writing and the Pt film thickness in Example 2 of the present invention. FIG. 8 is a graph showing the relationship between the required write current and the film thickness of the second underlayer in Example 3 of the present invention. FIG. 9 is a graph showing the relationship between the perpendicular magnetic anisotropy constant and the film thickness of the second underlayer in Example 3 of the present invention. FIG. 10 is a graph showing the relationship between the perpendicular magnetic anisotropy constant and the annealing temperature in Example 4 of the present invention.

A magnetic memory according to an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 2 is a schematic cross-sectional view showing the configuration of the magnetoresistive element 70 used in the memory cell of the magnetic memory according to the embodiment of the present invention. Each memory cell includes a magnetoresistive element 70. The magnetoresistive effect element 70 includes a domain wall motion layer 10, a spacer layer 20, and a reference layer 30.

  The domain wall motion layer 10 is formed of a ferromagnetic material having perpendicular magnetic anisotropy. The domain wall motion layer 10 includes a region in which the magnetization direction can be reversed, and stores data according to the magnetization state. More specifically, the domain wall motion layer 10 includes a first magnetization fixed region 11a, a second magnetization fixed region 11b, and a magnetization free region 13.

The magnetization fixed regions 11a and 11b are provided adjacent to the magnetization free region 13, respectively.
The magnetizations of the magnetization fixed regions 11a and 11b are fixed in opposite directions (antiparallel). In the example of FIG. 2, the magnetization direction of the first magnetization fixed region 11a is fixed in the + z direction, and the magnetization direction of the second magnetization fixed region 11b is fixed in the −z direction. As a magnetization fixing method, for example, a method of providing a hard layer (not shown) whose magnetization is fixed in the + z / −z direction adjacent to each of the magnetization fixed regions 11 a and 11 b can be considered.

  The magnetization direction of the magnetization free region 13 can be reversed and can be either the + z direction or the −z direction. Therefore, the domain wall 12 (12 a or 12 b) is formed in the domain wall moving layer 10 in accordance with the magnetization direction of the magnetization free region 13. In the example of FIG. 2, when the magnetization direction of the magnetization free region 13 is the + z direction, a domain wall 12b is formed between the magnetization free region 13 and the second magnetization fixed region 11b. On the other hand, when the magnetization direction of the magnetization free region 13 is the −z direction, the domain wall 12a is formed between the magnetization free region 13 and the first magnetization fixed region 11a. That is, the domain wall motion layer 10 has at least one domain wall 12 (12 a or 12 b), and the position of the domain wall 12 corresponds to the magnetization direction of the magnetization free region 13.

  FIG. 3 is a plan view showing the structure of the domain wall motion layer 10. As shown in FIG. 3, the magnetization fixed regions 11 a and 11 b are formed to have a width larger than that of the magnetization free region 13. Here, the “width” of the magnetization fixed regions 11a and 11b and the magnetization free region 13 is the direction in which the first magnetization fixed region 11a, the magnetization free region 13 and the second magnetization fixed region 11b are arranged (in FIG. 3, the x-axis direction). Note that it is defined in the direction perpendicular to (). As described later, the fact that the width of the magnetization fixed regions 11a and 11b is larger than the width of the magnetization free region 13 means that the movement of the domain wall is stopped near the boundary between the magnetization free region 13 and the magnetization fixed region 11a or 11b. have.

  Returning to FIG. 2, the spacer layer 20 is provided adjacent to the domain wall motion layer 10. In particular, the spacer layer 20 is provided so as to be adjacent to at least the magnetization free region 13 of the domain wall motion layer 10. The spacer layer 20 is made of a nonmagnetic material. More preferably, it is formed of an insulator.

  The reference layer 30 is provided adjacent to the spacer layer 20 on the side opposite to the domain wall motion layer 10. That is, the reference layer 30 is connected to the domain wall motion layer 10 (magnetization free region 13) through the spacer layer 20. The reference layer 30 is made of a ferromagnetic material, and its magnetization direction is fixed in one direction. Preferably, like the domain wall motion layer 10, the reference layer 30 is also formed of a ferromagnetic material having perpendicular magnetic anisotropy. In this case, the magnetization direction of the reference layer 30 is fixed in the + z direction or the −z direction. In the example of FIG. 2, the magnetization direction of the reference layer 30 is fixed in the + z direction.

  The domain wall motion layer 10 (magnetization free region 13), the spacer layer 20, and the reference layer 30 described above form a magnetic tunnel junction (MTJ). That is, the domain wall motion layer 10 (magnetization free region 13), the spacer layer 20, and the reference layer 30 correspond to a free layer, a barrier layer, and a pinned layer in the MTJ.

  Electrode layers (not shown) are electrically connected to both ends of the domain wall motion layer 10 respectively. In particular, two electrode layers (not shown) are provided so as to be connected to the magnetization fixed regions 11a and 11b, respectively. These electrode layers are used to introduce a write current into the domain wall motion layer 10. These electrode layers can be connected to both ends of the domain wall motion layer 10 via the hard layer described above. Further, another electrode layer (not shown) is electrically connected to the reference layer 30.

  In addition, the underlayer 40 is provided on the substrate side of the domain wall motion layer 10. The domain wall motion layer 10 is formed on the base layer 40 by using the base layer 40 as a base. One feature of the magnetic memory of the present embodiment is that the underlayer 40 is configured so that the domain wall motion layer 10 is grown with a favorable fcc (111) orientation and a desired perpendicular magnetic anisotropy is realized. It is in. The structure and function of the foundation layer 40 will be described in detail later.

  Next, a data storage state of the magnetoresistive effect element according to the embodiment of the present invention will be described.

  Here, a description will be given using the example of FIG. However, it is assumed that the magnetization directions of the magnetization fixed regions 11a and 11b of the domain wall motion layer 10 are fixed in the + z direction and the −z direction, respectively, and the magnetization direction of the reference layer 30 is fixed in the + z direction.

  In the example of FIG. 2, when the magnetization direction of the magnetization free region 13 of the domain wall moving layer 10 is the + z direction, the domain wall 12b is formed at the boundary between the magnetization free region 13 and the second magnetization free region 11b. The magnetization direction of the magnetization free region 13 and the magnetization direction of the reference layer 30 are parallel to each other. Therefore, the MTJ resistance value is relatively small. Such a magnetization state is associated with, for example, a storage state of data “0”.

  On the other hand, in FIG. 2, when the magnetization direction of the magnetization free region 13 of the domain wall moving layer 10 is the −z direction, the domain wall 12 a is formed at the boundary between the magnetization free region 13 and the first magnetization free region 11 a. The magnetization direction of the magnetization free region 13 and the magnetization direction of the reference layer 30 are antiparallel to each other. Accordingly, the MTJ resistance value is relatively large. Such a magnetization state is associated with a storage state of data “1”, for example.

  In this way, two storage states are realized corresponding to the magnetization state of the domain wall motion layer 10, that is, the domain wall position in the first domain wall motion layer 10. However, the correspondence between the magnetization state defined in the above description and the two storage states is arbitrary. That is, the domain wall motion layer 10 has at least one domain wall 12 (12 a or 12 b), and the position of the domain wall 12 corresponds to the magnetization direction of the magnetization free region 13. Therefore, the domain wall motion layer 10 stores data corresponding to the position of the domain wall 12.

  Subsequently, a method of writing data to the memory cell in this embodiment will be described with reference to FIG. 2A.

  A case where data “1” is written when the domain wall motion layer 10 is in the data “0” state (the magnetization direction of the magnetization free region 13 and the magnetization direction of the reference layer 30 are parallel to each other) will be described. In this case, a write current is passed from the first magnetization free region 11a to the second magnetization free region 11b via the magnetization free region 13. The conduction electrons flow from the second magnetization fixed region 11b to the first magnetization fixed region 11a via the magnetization free region 13. At this time, a spin transfer torque (STT) acts on the domain wall 12b located in the vicinity of the boundary between the second magnetization fixed region 11b and the magnetization free region 13, and the domain wall 12b acts on the first magnetization fixed region 11a. Move towards. That is, current induced domain wall movement occurs. Here, since the width of the first magnetization fixed region 11 a is larger than the width of the magnetization free region 13, the write current (density) is higher than the boundary between the first magnetization fixed region 11 a and the magnetization free region 13. Therefore, the movement of the domain wall 12 stops near the boundary. In this way, the domain wall 12b moves to the vicinity of the boundary between the first magnetization fixed region 11a and the magnetization free region 13, and data “1” is written.

  Next, a case where data “0” is written when the domain wall motion layer 10 is in the data “1” state (the magnetization direction of the magnetization free region 13 and the magnetization direction of the reference layer 30 are antiparallel to each other) will be described. To do. In that case, a write current is passed from the second magnetization fixed region 11 b to the first magnetization fixed region 11 a via the magnetization free region 13. The conduction electrons flow from the first magnetization fixed region 11 a to the second magnetization fixed region 11 b via the magnetization free region 13. At this time, a spin transfer torque acts on the domain wall 12a located near the boundary between the first magnetization fixed region 11a and the magnetization free region 13, and the domain wall 12a moves toward the second magnetization fixed region 11b. That is, current induced domain wall movement occurs. Here, since the width of the second magnetization fixed region 11 b is larger than the width of the magnetization free region 13, the write current (density) is higher than the boundary between the second magnetization fixed region 11 b and the magnetization free region 13. Therefore, the movement of the domain wall 12 stops near the boundary. In this way, the domain wall 12a moves to the vicinity of the boundary between the second magnetization fixed region 11b and the magnetization free region 13, and data “0” is written.

  Note that no state change occurs when data “0” is written in the data “0” state and data “1” is written in the data “1” state. That is, overwriting is possible.

  On the other hand, in the memory cell of this embodiment, data reading is performed according to the following procedure.

  In the present embodiment, data reading is performed by utilizing a tunneling magnetoresistive effect (TMR effect). For this purpose, a read current is passed in a direction penetrating the MTJ (the magnetization free region 13 of the domain wall motion layer 10, the spacer layer 20, and the reference layer 30). Note that the direction of the read current is arbitrary. At this time, when the magnetoresistive element 70 is in the data “0” state, the resistance value of the MTJ is relatively small. In the data “1” state, the MTJ resistance value is relatively large. Therefore, data can be read by detecting the resistance value.

  Next, a magnetic memory cell having the magnetoresistive effect element 70 according to the present embodiment will be described.

  FIG. 4 is a schematic circuit diagram showing a configuration example of the magnetic memory cell 80 for 1 bit according to the embodiment of the present invention. The magnetic memory cell 80 has a 2T-1MTJ (2 Transistors-1 Magnetic Tunnel Junction) configuration including a magnetic memory element 70 and two transistors TRa and TRb. The magnetoresistive effect element 70 is a three-terminal element, and is connected to the word line WL, the ground line GL, and the bit line pair BLa, BLb. For example, the terminal connected to the reference layer 30 is connected to the ground line GL. A terminal connected to the first magnetization fixed region 11a of the domain wall motion layer 10 is connected to the bit line BLa via the transistor TRa. A terminal connected to the second magnetization fixed region 11b of the domain wall motion layer 10 is connected to the bit line BLb via the transistor TRb. The gates of the transistors TRa and TRb are connected to a common word line WL.

  During the write operation, the word line WL is set to the high level, and the transistors TRa and TRb are turned on. In addition, one of the bit line pair BLa and BLb is set to a high level, and the other is set to a low level (ground level). As a result, a write current flows between the bit line BLa and the bit line BLb via the transistors TRa and TRb and the domain wall motion layer 10.

  During the read operation, the word line WL is set to a high level, and the transistors TRa and TRb are turned on. Further, the bit line BLa is set to an open state, and the bit line BLb is set to a high level. As a result, the read current Iread flows from the bit line BLb through the MTJ of the magnetoresistive effect element 70 to the ground line GL.

  Next, the circuit configuration of the magnetic random access memory 90 according to the present embodiment will be described. FIG. 5 is a block diagram showing a configuration example of the magnetic random access memory 90 according to the present embodiment. The magnetic random access memory 90 includes a memory cell array 91, an X driver 92, a Y driver 93, and a controller 94. The memory cell array 91 is composed of a plurality of magnetic memory cells 80 arranged in an array. As shown in FIG. 3 described above, each magnetic memory cell 80 is connected to the word line WL, the ground line GL, and the bit line pair BLa, BLb. The X driver 92 is connected to a plurality of word lines WL, and drives a selected word line connected to the accessed magnetic memory cell 80 among the plurality of word lines WL. The Y driver 93 is connected to a plurality of bit line pairs BLa and BLb, and sets each bit line to a state corresponding to a write operation or a read operation. The controller 94 controls each of the X driver 92 and the Y driver 93 according to a write operation or a read operation.

Next, the material and configuration of the domain wall motion layer 10 of the magnetoresistive effect element 70 in the present embodiment will be described. As disclosed in Non-Patent Document 3 and Patent Document 3 described above, when the domain wall motion layer has perpendicular magnetic anisotropy, the domain wall motion layer is smaller than other methods. It is possible to cause domain wall movement by the write current. Non-Patent Document 4 (A. Thiaville et al., “Domain wall motion by spin-polarized current: a
micromagnetic study ", JOURNAL OF APPLIED PHYSICS, VOL.95, NO.11, pp.7049-7051,2004.), the current-induced domain wall motion is more likely to occur as the parameter: gμBP / 2eMs increases. g is a Lande g factor, μB is a Bohr magneton, P is a spin polarizability, e is an electron's elementary charge, Ms is a saturation magnetization, and g, μB, and e are physical constants, thus reducing a write current. For this purpose, it is effective to increase the spin polarizability P of the domain wall motion layer 10 and decrease the saturation magnetization Ms.

From the viewpoint of saturation magnetization, transition metal-based alternate laminated films such as Co / Ni, Co / Pt, Co / Pd, CoFe / Ni, CoFe / Pt, and CoFe / Pd are promising as the domain wall motion layer 10. It is known that the saturation magnetization of these materials is relatively small. When such a transition metal-based laminated film is more generalized, the first domain wall motion layer 10 has a laminated structure in which a first layer and a second layer are laminated. The first layer contains an alloy made of a plurality of materials selected from any one of Fe, Co, and Ni, or a group thereof. The second layer contains Pt, Pd, Au, Ag, Ni, Cu, or an alloy made of a plurality of materials selected from these groups.

  Of the above laminated films, Co / Ni has a high spin polarizability. Therefore, it can be said that the Co / Ni laminated film is particularly suitable as the domain wall motion layer 10. In fact, the inventors have confirmed through experiments that domain wall movement with high controllability can be realized by using Co / Ni.

By the way, the magnetic material of the domain wall motion layer 10 as described above has an fcc structure and (111) plane orientation. That is, the (111) plane of the domain wall motion layer 10 is oriented in the direction perpendicular to the substrate. Non-Patent Document 5 (GHODaalderop et al., “Prediction and Confirmation of
Perpendicular Magnetic Anisotropy in Co / Ni Multilayers ”, PHYSICAL REVIEW
According to LETTERS, VOL.68, NO.5, pp.682-685, 1992.), the perpendicular magnetic anisotropy of the laminated film as described above is manifested by the interfacial magnetic anisotropy at the interface of these films. . Therefore, in order to achieve good perpendicular magnetic anisotropy in the domain wall motion layer 10, it is preferable to provide a “underlayer” that allows the above-described magnetic material to grow with good fcc (111) orientation.

  In the present embodiment, the underlayer 40 is configured such that the domain wall motion layer 10 can be grown with good fcc (111) orientation and good perpendicular magnetic anisotropy is realized. Hereinafter, the underlayer 40 will be described in detail.

  The underlayer 40 has a two-layer structure, that is, includes a first underlayer 41 and a second underlayer 42. A second underlayer 42 is formed on the first underlayer 41, and the domain wall motion layer 10 is formed on the second underlayer 42. The first underlayer 41 contains a Group 4 to Group 6 element. That is, the first underlayer 41 is made of any one of Group 4 to Group 6 metals such as Ti, Zr, Nb, Mo, Hf, Ta, and W, or an alloy made of a plurality of materials selected from these groups. contains. On the other hand, the second underlayer 42 contains a Group 9 to Group 11 element. That is, the second underlayer 42 is a material selected from any of Group 9 to Group 11 metals having an fcc structure such as Cu, Rh, Pd, Ag, Ir, Pt, and Au, or a group thereof. An alloy consisting of The first base layer 41 and the second base layer 42 do not need to be made of a single metal of the material exemplified above, and may be an alloy formed therebetween. Furthermore, the present invention can be implemented even if the above materials and alloys are the main materials and other materials are included within an appropriate range. It is also possible to adjust so as to obtain more desired characteristics by adding an appropriate material.

  The reason why such a combination of the first underlayer 41 and the second underlayer 42 is preferable is as follows. First, the Group 4 to Group 6 metal used as the first underlayer 41 grows in an amorphous state in a region where the film thickness is thin, and its surface energy increases. Therefore, such a first underlayer 41 can produce a close-packed surface (lowest surface energy surface) orientation of a crystal grown thereon. That is, when the ninth to eleventh group metals having the fcc structure grow as the second underlayer 42 on the first underlayer 41, the (111) plane orientation which is the most dense surface is realized. Such a second underlayer serves as a template for crystal orientation of the domain wall motion layer 10. As a result, good fcc (111) orientation is also achieved in the domain wall motion layer 10.

  In particular, when focusing on a Co / Ni laminated film having a low saturation magnetization and a high spin polarizability, a suitable underlayer 40 has a laminated structure of a first underlayer 41 and a second underlayer 42 formed of the above materials. It has been found that suitable properties can be obtained with respect to Co / Ni laminated films.

  Here, the inventor further examined the following points this time. That is, when the domain wall motion layer is formed of a ferromagnetic material having perpendicular magnetic anisotropy, the inventor can further reduce the write current if the spin polarizability of the domain wall motion layer can be further increased. is there. By clarifying the relationship between spin polarizability and perpendicular magnetic anisotropy (herein, magnetic anisotropy constant; Ku is a parameter) in ferromagnetic materials, the optimum perpendicular magnetic anisotropy for the domain wall moving layer is obtained. It is considered that the write current can be further reduced by further increasing the spin polarizability by providing the same.

  As a result of the examination, it has been found that it is preferable to set the perpendicular magnetic anisotropy at least within a certain range in order to lower the write current (domain wall movement current) for causing the domain wall movement. When the perpendicular magnetic anisotropy is expressed by the magnetic anisotropy constant of the domain wall moving layer 10, the upper and lower limits of the range are as follows: The upper limit is the magnetic anisotropy inherent to the ferromagnetic material of the domain wall moving layer 10 The lower limit is a magnetic anisotropy constant that is the minimum necessary for the domain wall motion layer 10 to maintain perpendicular magnetic anisotropy.

  The magnetic anisotropy constant of the domain wall motion layer 10 as the upper limit is smaller than the original value of the ferromagnetic material of the domain wall motion layer. Here, the intrinsic magnetic anisotropy constant of the material is a value theoretically predicted from the inherent physical properties (physical property values) of the material. For example, when using an alternate laminated film of transition metal-based tax as the domain wall motion layer 10, considering the physical properties inherent to the transition metal-based material, the structure of the laminated structure, the ideal perpendicular magnetic anisotropy, etc. The value is theoretically predicted by the theoretical calculation (simulation) to be performed. If the magnetic anisotropy constant of the domain wall motion layer 10 is smaller than the original value of the material, the spin polarizability is considered to be relatively high. The reason is as follows.

The origin of perpendicular magnetic anisotropy includes crystal magnetic anisotropy and interfacial magnetic anisotropy. In the interfacial magnetic anisotropy, the spin initiation interaction of d electrons having anisotropic electron orbits may play an important role. Here, increasing the perpendicular magnetic anisotropy corresponds to lowering the energy level of the d electrons. On the other hand, the domain wall motion current (write current) is governed by the difference in the number of positive and negative spins of d electrons near the Fermi energy contributing to conduction, that is, the spin polarizability. Therefore, in a material with strong perpendicular magnetic anisotropy, the orbital energy of d electrons is reduced, and the d electrons contributing to conduction are reduced below Fermi energy. Therefore, it is considered that the difference in the number of positive and negative spins is reduced, and as a result, the spin polarizability is reduced. From the above, in such a case, the perpendicular magnetic anisotropy is moderately weakened to increase the d electron energy level and increase the d electrons in the vicinity of the Fermi energy, thereby increasing the spin spin rate. Can be realized.

  On the other hand, the magnetic anisotropy constant of the domain wall motion layer 10 as the lower limit is larger than the minimum value at which the domain wall motion layer 10 can maintain the perpendicular magnetic anisotropy. That is, the anisotropic magnetic field of the domain wall motion layer 10 needs to be sufficiently large to overcome the demagnetizing field and direct the magnetization in the vertical direction. Here, the value of the minimum magnetic anisotropy constant capable of maintaining the perpendicular magnetic anisotropy is in the vicinity of the boundary between the state in which the domain wall moving layer 10 has the perpendicular magnetic anisotropy and the state in which it does not have the magnetic anisotropy. The value of the magnetic anisotropy constant when on the state side having perpendicular magnetic anisotropy. The state having perpendicular magnetic anisotropy means that the magnetization direction of the domain wall motion layer 10 is generally in the ± z direction. Specifically, the ± z direction component of the magnetization direction of the domain wall motion layer 10 is at least larger than the ± x direction component and the ± y direction component (both components in the direction parallel to the substrate surface). The fact that the magnetic anisotropy constant of the domain wall motion layer 10 takes such a value is considered to mean that the current induced domain wall motion type domain wall motion layer 10 has perpendicular magnetic anisotropy. In that case, as described in Patent Document 3 and Non-Patent Document 3, the write current can be reduced.

  In addition, the inventor confirmed that the perpendicular magnetic anisotropy of the domain wall moving layer 10 described above is a state in which the underlayer and the domain wall moving layer are sequentially formed in this order using a vacuum film forming apparatus or the like (immediately after film formation) In the experiment, it was confirmed that the magnitude of perpendicular magnetic anisotropy was different when annealed (heat treatment) at an appropriate temperature after film formation. Immediately after the film formation, the domain wall motion layer 10 has already overcome the demagnetizing field, and the domain wall motion layer with strong perpendicular magnetic anisotropy in which the magnetization is aligned in the vertical direction has been subjected to the above-described annealing treatment to cause more perpendicular magnetic property. Strengthens the directionality and tries to approach the perpendicular magnetic anisotropy theoretically predicted from the inherent physical properties (physical properties) of the material. On the other hand, in the domain wall moving layer 10 in which the anisotropic magnetic field of the domain wall moving layer 10 is smaller than the demagnetizing field immediately after the film formation and the magnetization is directed in the plane, the anisotropic magnetic field increases due to the annealing treatment, and the anti magnetic field increases. By overcoming the magnetic field, perpendicular magnetic anisotropy is imparted. Thus, the phenomenon in which the perpendicular magnetic anisotropy immediately after the film formation is increased by the annealing treatment was confirmed here by experimentally observing the perpendicular magnetic anisotropy constant of the domain wall motion layer 10. Below, the cause of the phenomenon in which the perpendicular magnetic anisotropy of the domain wall motion layer 10 is increased by the above-described annealing treatment is estimated. The underlayer immediately after film formation and the domain wall motion layer 10 grown under the influence are not entirely in the original fcc (111) orientation, but are partially oriented in different orientations. Growing. Here, by performing heat treatment at an appropriate temperature after the film formation, each constituent element is rearranged at an energetically stable lattice position, so that the state approaches a more ideal fcc (111) orientation. Since the perpendicular magnetic anisotropy is further increased, it is considered that the perpendicular magnetic anisotropy constant is increased as a result.

  The above examination content was confirmed by the experimental result of the Example shown below. Each example will be described below.

  In Example 1, in the configuration of the magnetoresistive effect element 70 to which the underlayer is applied as illustrated in FIG. 2, the first underlayer 41 and the second underlayer 42 are sequentially formed in this order as the underlayer 40. Then, a Ta film having a thickness of 3 nm was used as the first underlayer 41, and a Pt film was used as the second underlayer 42. As the domain wall motion layer 10, a Co / Ni laminated film in which a 0.3 nm thick Co film and a 0.6 nm thick Ni film were alternately laminated five times was used. In the configuration described above, the magnetoresistive element 70 was manufactured by changing the thickness of the Pt film used as the second underlayer 42 in the range of 0 nm to 2 nm. The width of the magnetoresistive element 70 is 100 nm. In this element, after forming the base layer 40 and the domain wall motion layer 10, annealing is performed in vacuum at 300 ° C. for 2 hours.

Using this magnetoresistive effect element, the current value at which domain wall motion occurs was measured. This current value indicates the minimum value of the write current necessary for causing the domain wall movement in the domain wall moving layer 10. For details of the experimental method, see Non-Patent Document 6 (T. Suzuki et al., “Evaluation of Scalability for Current-Driven Domain.
Wall Motion in a Co / Ni Multilayer Strip for Memory Applications ”, IEEE
TRANSACTIONS ON MAGNETICS, VOL.45, No.10, pp.3776-3779, (2009).

FIG. 6 shows the Pt film thickness dependence of the current value causing the domain wall motion and the perpendicular magnetic anisotropy constant when the film thickness of the Pt film used as the second underlayer 42 is changed. As can be seen from FIG. 6, the perpendicular magnetic anisotropy constant Ku increases and the current value necessary for writing increases as the thickness of the Pt film used as the second underlayer 42 increases. In order to operate at a write current value of 0.5 mA or less, the thickness of the second underlayer Pt is desirably 1 nm or less, and the value of the perpendicular magnetic anisotropy constant Ku at this time is 3.7 × 10 ⁶ (erg / Cc) and 6.43 × 10 ⁶ (erg / cc) or less.

  From the results shown above, the write current value increases as the thickness of the Pt film used as the second underlayer 42 increases, and the magnetic properties of the domain wall motion layer 10 are relatively low in the perpendicular magnetic anisotropy constant Ku. You can see that it is getting bigger. This is because as the Pt film thickness increases, the (111) orientation of the Pt film increases, and as a result, the (111) orientation of the domain wall motion layer 10 improves, and as a result, the perpendicular magnetic anisotropy of the domain wall motion layer 10 increases. As a result of the increase, it is considered that the perpendicular magnetic anisotropy constant Ku is increased.

  Therefore, in order to keep the write current value as relatively low as about 0.5 mA, it is possible to adjust the film thickness of the second underlayer 42 and control the perpendicular magnetic anisotropy of the domain wall motion layer 10 to a certain value or less. It turns out that it is preferable.

In Example 2, in the configuration of the magnetoresistive effect element 70 to which the underlayer is applied as shown in FIG. 2, the first underlayer 41 and the second underlayer 42 are sequentially formed in this order as the underlayer 40. A Ta film having a thickness of 5 nm was used as the first underlayer 41, and a Pt film was used as the second underlayer. As the domain wall motion layer 10, a Co / Ni laminated film in which a 0.3 nm thick Co film and a 0.6 nm thick Ni film were alternately laminated five times was used. In the configuration described above, the magnetoresistive element 70 was manufactured by changing the thickness of the Pt film used as the second underlayer 42 in the range of 0 nm to 2 nm. The width of the magnetoresistive element 70 is 100 nm. In this element, after forming the base layer 40 and the domain wall motion layer 10, annealing is performed in a vacuum at 300 ° C. for 2 hours.
Using this magnetoresistive effect element, the current value at which domain wall motion occurs was measured.

FIG. 7 shows the Pt film thickness dependence of the current value causing the domain wall motion and the perpendicular magnetic anisotropy constant when the film thickness of the Pt film used as the second underlayer 42 is changed. As shown in FIG. 7, it can be seen that as the Pt film thickness increases, the perpendicular magnetic anisotropy constant Ku increases and the current value necessary for writing also increases. In order to operate at a write current value of 0.5 mA or less, the thickness of the Pt film used as the second underlayer 42 is desirably 0.9 nm or less, and the value of the perpendicular magnetic anisotropy constant Ku at this time is It is in the range of 3.8 × 10 ⁶ (erg / cc) to 5.6 × 10 ⁶ (erg / cc).

  In Example 3, in the configuration of the magnetoresistive effect element 70 to which the underlayer 40 is applied as shown in FIG. 2, any one of Ti, Zr, Nb, Mo, Hf, Ta, and W is formed on the substrate, or The first underlayer 41 made of an alloy of two or more materials selected from these groups is used, and any one of Cu, Rh, Pd, Ag, Ir, Pt, Au, or a group thereof is formed thereon. The magnetoresistive effect element 70 in which the second underlayer 42 made of an alloy of two or more materials selected from the above was formed and the domain wall motion layer 10 was further laminated was produced. Here, the film thickness of the second underlayer 42 was changed in the range of 0 nm to 2 nm. FIG. 8 shows the relationship between the film thickness of the second underlayer and the current value by measuring the current value at which the domain wall motion occurs using the magnetoresistive effect element described above. In the figure, the maximum value and the minimum value of the write current of the magnetoresistive effect element 70 using the base layer 40 obtained by the combination of each of the first base layer 41 and the second base layer 42, and those values are shown. The average values were plotted together.

  In FIG. 8, when the film thickness of the second underlayer is 0.9 nm or less, the maximum value of the write current value is 0. 10 mm when any of the first underlayer 41 and the second underlayer 42 described above is used. It can be seen that the domain wall motion can be performed without exceeding 5 mA.

FIG. 9 shows a plot of the relationship between the perpendicular magnetic anisotropy constant of the element whose current value was measured in FIG. 8 and the film thickness of the second underlayer 42. From FIG. 9, when the thickness of the second underlayer 42 is 0.9 nm or less, the perpendicular magnetic anisotropy constant is 3 × 10 ⁶ (erg / cc) ≦ Ku ≦ 7 × 10 ⁶ (erg / cc). ). Therefore, by using the domain wall motion layer 10 having the perpendicular magnetic anisotropy constant in the above-described range, the domain wall motion operation can be performed in a range where the write current value for domain wall motion does not exceed 0.5 mA.

  In each of the embodiments described above, the results are obtained when annealing at 300 ° C. is performed in vacuum after the underlayer 40 and the domain wall motion layer 10 are formed. As described above, by annealing, the orientation of the second underlayer 42 and, for example, the Co / Ni laminated film laminated thereon is enhanced, and perpendicular magnetic anisotropy is imparted. In the state in which the Co / Ni laminated film before annealing is formed, the Co / Ni laminated film does not have perpendicular magnetic anisotropy but has in-plane magnetic anisotropy.

As Example 4, the relationship between the perpendicular magnetic anisotropy constant Ku of the domain wall motion layer 10 and the annealing temperature will be described. FIG. 10 shows domain wall motion when a Ta film having a film thickness of 5 nm is used as the first underlayer 41, a Pt film is used as the second underlayer 42, and the Pt film thickness is 0.9 nm and 0 nm (when there is no Pt film). The annealing temperature dependence of the perpendicular magnetic anisotropy constant Ku of the layer 10 is shown. Here, as the domain wall motion layer 10, a Co / Ni laminated film in which a Co film having a film thickness of 0.3 nm and a Ni film having a film thickness of 0.6 nm are alternately laminated five times was used. Here, the perpendicular magnetic anisotropy constant Ku is 2.8 × 10 ⁶ (erg / cc) or more considering the magnetization of the domain wall motion layer 10 described above, and the domain wall motion layer 10 becomes a perpendicular magnetization film. From FIG. 10, it can be seen that when the Pt film thickness is 0.9 nm, a perpendicular magnetization film is obtained when the annealing temperature is in the range of 200 ° C. to 350 ° C. Therefore, the annealing temperature is more preferably in the range of 250 ° C to 350 ° C.

  In each of the embodiments described above, the Ta film is used as the first base layer 41, the Pt film is used as the second base layer 42, and the Co / Ni laminated film is used as the domain wall motion layer. The material is not limited. As the first underlayer 41, the same effect can be obtained by using any one of Ti, Zr, Nb, Mo, Hf, Ta, W or an alloy composed of two or more selected from these groups as a thin film material. Is confirmed to be obtained. In addition, as the second underlayer 42, the same is achieved by using, as a thin film material, an alloy composed of Cu, Rh, Pd, Ag, Ir, Pt, Au, or two or more selected from these groups. It has been confirmed that the effect of. The domain wall motion layer 10 has a laminated structure in which first layers and second layers are alternately laminated, and the first layer is one of Fe, Co, Ni, or a group thereof. And the second layer is made of any one of Pt, Pd, Au, Ag, Ni, and Cu, or two or more materials selected from these groups. The same effect has been confirmed using a laminated film containing an alloy.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited to the above-described embodiments and examples. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

  A part or all of the above embodiments can be described as in the following supplementary notes, but is not limited thereto.

(Appendix 1)
Comprising a memory cell;
The memory cell is
A first underlayer made of two or more materials selected from Ti, Zr, Nb, Mo, Hf, Ta, W, or a group thereof;
Two or more selected from Cu, Rh, Pd, Ag, Ir, Pt, Au, or a group formed on the first base layer so as to be in contact with the first base layer A second underlayer made of a material;
A domain wall motion layer having perpendicular magnetic anisotropy formed on the second underlayer so as to be in contact with the second underlayer;
The domain wall motion layer has a magnetization free region whose magnetization direction is reversible,
The magnetization direction of the magnetization free region is reversed by current induced domain wall motion by passing a write current through the magnetization free region,
A magnetic memory in which the film thickness of the second underlayer is 0.9 nm or less.
(Appendix 2)
The magnetic memory according to appendix 1, wherein
The magnetic memory in which the domain wall motion layer has an fcc structure and has a (111) plane orientation.
(Appendix 3)
The magnetic memory according to appendix 1 or 2,
The domain wall motion layer has a laminated structure in which first layers and second layers are alternately laminated,
The first layer contains an alloy composed of one or more materials selected from Fe, Co, Ni, or a group thereof,
The second layer includes a Pt, Pd, Au, Ag, Ni, Cu, or an alloy made of one or more materials selected from these groups.
(Appendix 4)
The magnetic memory according to any one of appendices 1 to 3,
A magnetic memory in which a perpendicular magnetic anisotropy constant of the domain wall motion layer is 3 × 10 ⁶ (erg / cc) or more and 7 × 10 ⁶ (erg / cc) or less.
(Appendix 5)
Forming a first underlayer composed of two or more materials selected from Ti, Zr, Nb, Mo, Hf, Ta, W, or a group thereof;
Forming a second underlayer made of Cu, Rh, Pd, Ag, Ir, Pt, Au, or two or more materials selected from the group on the first underlayer;
Forming a domain wall motion layer having a magnetization free region whose magnetization direction is reversible and having perpendicular magnetic anisotropy on the second underlayer;
Providing an electrode for flowing a write current in the magnetization free region that reverses the magnetization direction of the magnetization free region by current-induced domain wall movement,
A method for manufacturing a magnetic memory, wherein the film thickness of the second underlayer is 0.9 nm or less.
(Appendix 6)
The manufacturing method according to attachment 5, wherein
A method for manufacturing a magnetic memory, wherein the domain wall motion layer has an fcc structure and has a (111) plane orientation.
(Appendix 7)
The manufacturing method according to appendix 5 or 6,
The step of forming the domain wall motion layer includes
Immediately after formation, a step of forming a ferromagnetic layer having in-plane magnetic anisotropy,
Providing a perpendicular magnetic anisotropy to the ferromagnetic layer by an annealing step.
(Appendix 8)
The manufacturing method according to appendix 7,
An annealing temperature in the annealing step is in a range of 250 ° C. to 350 ° C. Magnetic memory manufacturing method.
(Appendix 9)
The manufacturing method according to any one of appendices 5 to 8,
The perpendicular magnetic anisotropy constant of the domain wall motion layer provided with perpendicular magnetic anisotropy by the annealing step is in a range of 3 × 10 ⁶ (erg / cc) to 7 × 10 ⁶ (erg / cc). A method of manufacturing a magnetic memory.

10, 110: Domain wall moving layers 11a, 111a: First magnetization fixed region 11b, 111b: Second magnetization fixed region 12, 12a, 12b, 112, 112a, 112b: Domain wall 13, 113: Magnetization free region 20, 120: Spacer Layers 30 and 130: Reference layer 40: Underlayer 41: First underlayer 42: Second underlayer 70: Magnetoresistive element 80: Magnetic memory cell 90: Magnetic random access memory 91: Memory cell array 92: X driver 93: Y driver 94: controller

Claims (9)

Comprising a memory cell;
The memory cell is
A first underlayer made of two or more materials selected from Ti, Zr, Nb, Mo, Hf, Ta, W, or a group thereof;
Two or more selected from Cu, Rh, Pd, Ag, Ir, Pt, Au, or a group formed on the first base layer so as to be in contact with the first base layer A second underlayer made of a material;
A domain wall motion layer having perpendicular magnetic anisotropy formed on the second underlayer so as to be in contact with the second underlayer;
The domain wall motion layer has a magnetization free region whose magnetization direction is reversible,
The magnetization direction of the magnetization free region is reversed by current induced domain wall motion by passing a write current through the magnetization free region,
A magnetic memory in which the film thickness of the second underlayer is 0.9 nm or less. The magnetic memory according to claim 1,
The magnetic memory in which the domain wall motion layer has an fcc structure and has a (111) plane orientation. The magnetic memory according to claim 1, wherein
The domain wall motion layer has a laminated structure in which first layers and second layers are alternately laminated,
The first layer contains an alloy composed of one or more materials selected from Fe, Co, Ni, or a group thereof,
The second layer includes a Pt, Pd, Au, Ag, Ni, Cu, or an alloy made of one or more materials selected from these groups. The magnetic memory according to any one of claims 1 to 3,
A magnetic memory in which a perpendicular magnetic anisotropy constant of the domain wall motion layer is 3 × 10 ⁶ (erg / cc) or more and 7 × 10 ⁶ (erg / cc) or less. Forming a first underlayer composed of two or more materials selected from Ti, Zr, Nb, Mo, Hf, Ta, W, or a group thereof;
Forming a second underlayer made of Cu, Rh, Pd, Ag, Ir, Pt, Au, or two or more materials selected from the group on the first underlayer;
Forming a domain wall motion layer having a magnetization free region whose magnetization direction is reversible and having perpendicular magnetic anisotropy on the second underlayer;
Providing an electrode for flowing a write current in the magnetization free region that reverses the magnetization direction of the magnetization free region by current-induced domain wall movement,
A method for manufacturing a magnetic memory, wherein the film thickness of the second underlayer is 0.9 nm or less. It is a manufacturing method of Claim 5, Comprising:
A method for manufacturing a magnetic memory, wherein the domain wall motion layer has an fcc structure and has a (111) plane orientation. It is a manufacturing method of Claim 5 or 6, Comprising:
The step of forming the domain wall motion layer includes
Immediately after formation, a step of forming a ferromagnetic layer having in-plane magnetic anisotropy,
Providing a perpendicular magnetic anisotropy to the ferromagnetic layer by an annealing step. It is a manufacturing method of Claim 7, Comprising:
An annealing temperature in the annealing step is in a range of 250 ° C. to 350 ° C. Magnetic memory manufacturing method. The manufacturing method according to any one of claims 5 to 8,
The perpendicular magnetic anisotropy constant of the domain wall motion layer provided with perpendicular magnetic anisotropy by the annealing step is in a range of 3 × 10 ⁶ (erg / cc) to 7 × 10 ⁶ (erg / cc). A method of manufacturing a magnetic memory.

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