Magnetoresistance effect element, magnetic memory and artificial intelligence system

Abstract

Provided are: a magneto-resistive element in which the direction of magnetization in a recording layer can be efficiently reversed with low resistance and without reducing reversal efficiency by a write current flowing in a heavy metal layer; a magnetic memory; and an artificial intelligence system. A magneto-resistive element 10 includes: a heavy metal layer 11 that is formed by laminating Ir layers 12 and Pt layers 13; a recording layer 16 that is provided so as to be opposed to the heavy metal layer 11 and that is formed by containing a first ferromagnetic layer having reversible magnetization; a reference layer 18 that is formed by containing a second ferromagnetic layer in which the direction of magnetization is fixed; and a barrier layer 17 that is sandwiched between the first ferromagnetic layer and the second ferromagnetic layer and that is formed of an insulator. The direction of magnetization in the first ferromagnetic layer is reversed by a write current flowing in the heavy metal layer 11.

Description

[Technical Field]

[0001] The present invention relates to a magnetoresistive element, a magnetic memory, and an artificial intelligence system. [Background technology]

[0002] Writing information is crucial for realizing spintronics integrated circuits. To electrically reverse magnetization in spintronics, spin-transfer magnetization reversal is one method. This method reverses the magnetization of a magnetic tunnel junction (MTJ) by passing a current through the MTJ. The MTJ consists of a recording layer containing a first ferromagnetic layer with reversible magnetization, a barrier layer made of an insulator, and a reference layer containing a second ferromagnetic layer with a fixed magnetization direction. Recently, spin-orbit torque (SOT)-induced magnetization reversal has been used to electrically reverse magnetization, and magnetic random access memory (MRAM) devices using this method have attracted attention.

[0003] An SOT-MRAM element is constructed by providing an MTJ including a recording layer, a barrier layer, and a reference layer on a heavy metal layer. When a current is passed through the heavy metal layer, a spin current is induced by spin-orbit interaction, and the spins polarized by the spin current flow into the recording layer, reversing the magnetization of the recording layer. As a result, the direction of magnetization in the recording layer switches between parallel and anti-parallel to the direction of magnetization in the reference layer, thereby recording data (Patent Documents 1 to 3).

[0004] In addition, an electronic neuron using SOT-MRAM elements has been proposed, in which the magnetization direction of the neuron is determined by the total synaptic current, and a resistive crossbar array is used that functions as a synapse to generate a bipolar current that is the weighted sum of input signals (Patent Document 4). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2016 / 021468 [Patent Document 2] International Publication No. 2016 / 159017 [Patent Document 3] International Publication No. 2019 / 159962 [Patent Document 4] US Patent Application Publication No. 2017 / 0330070 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when heavy metal elements such as β-W are used in the heavy metal layer of an SOT-MRAM element, the high resistivity of the heavy metal elements increases power consumption, although it is expected to improve the write efficiency.

[0007] Therefore, the present invention aims to provide a magnetoresistive effect element, a magnetic memory, and an artificial intelligence system that can efficiently reverse the direction of magnetization in the recording layer with low resistance and without reducing reversal efficiency by using a write current flowing through a heavy metal layer. [Means for solving the problem]

[0008] The concept of the present invention is as follows. [1] A heavy metal layer formed by laminating an Ir layer and a Pt layer; a recording layer including a first ferromagnetic layer having reversible magnetization, the recording layer being provided so as to face the heavy metal layer; a reference layer comprising a second ferromagnetic layer having a fixed direction of magnetization; a barrier layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer and made of an insulator; Equipped with A magnetoresistive element in which the direction of magnetization in the first ferromagnetic layer is reversed by a write current flowing through the heavy metal layer. [2] The magnetoresistive element according to [1], wherein the heavy metal layer is formed by repeatedly stacking the Ir layer and the Pt layer. [3] The magnetoresistive element according to [1] or [2], wherein the Pt layer that is the outermost layer of the heavy metal layer forms an interface with the recording layer. [4] The magnetoresistive element according to any one of [1] to [3], wherein the Pt layers of the heavy metal layer each have a thickness of more than 0.6 nm and not more than 1.5 nm. [5] The magnetoresistive element according to any one of [1] to [4], wherein the Ir layers of the heavy metal layer each have a thickness of 0.6 nm to 1.5 nm. [6] The magnetoresistive element according to any one of [1] to [5], wherein the ratio of the thickness of the Pt layer to the thickness of the Ir layer in the heavy metal layer is in the range of 1:0.5 to 1:0.8. [7] The magnetoresistive effect element according to [1], wherein the heavy metal layer is formed by stacking one layer of the Ir layer and one layer of the Pt layer, and a separate ferromagnetic layer is provided on the recording layer side and the opposite side of the recording layer. [8] A magnetoresistive effect element described in any one of [1] to [7], wherein the shapes of the recording layer, the barrier layer, and the reference layer as viewed in the stacking direction of the heavy metal layer are asymmetric with respect to any line in the direction along the write current in the heavy metal layer. [9] A magnetoresistive effect element described in any one of [1] to [7], wherein the shapes of the recording layer, the barrier layer, and the reference layer as viewed in the stacking direction of the heavy metal layer are symmetrical with respect to any line in the direction along the write current in the heavy metal layer.

[10] A magnetic memory comprising a plurality of magnetoresistive effect elements according to any one of [1] to [9], each including the recording layer, the barrier layer, and the reference layer, provided on the same heavy metal layer.

[11] An artificial intelligence system in which the magnetoresistive effect element according to any one of [1] to [7] is used in an electronic neuron to which a weighted sum of a resistive crossbar network is input.

[12] The artificial intelligence system described in

[11] , wherein the magnetoresistive effect element is used in a crosspoint memory of a resistive crossbar network. [Effects of the Invention]

[0009] According to the present invention, a magnetic recording medium comprises a heavy metal layer formed by stacking an Ir layer and a Pt layer, a recording layer including a first ferromagnetic layer having reversible magnetization and disposed opposite the heavy metal layer, a reference layer including a second ferromagnetic layer having a fixed magnetization direction, and a barrier layer sandwiched between the first and second ferromagnetic layers and composed of an insulator. Therefore, the direction of magnetization in the first ferromagnetic layer can be efficiently reversed by a write current flowing through the heavy metal layer with low resistance and without reducing reversal efficiency. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view schematically showing a magnetoresistive element according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the magnetoresistive element shown in FIG. [Figure 3] FIG. 3 is a diagram for explaining a method for writing data "0" to a magnetoresistive element storing data "1", and shows the initial state of magnetization. [Figure 4] FIG. 4 is a diagram for explaining a method for writing data "0" into a magnetoresistive element that stores data "1," and shows a state in which data has been written by passing a write current. [Figure 5] FIG. 5 is a diagram for explaining a method for writing data "1" to a magnetoresistive element storing data "0", and shows the initial state of magnetization. [Figure 6] FIG. 6 is a diagram for explaining a method for writing data "1" into a magnetoresistive element that stores data "0," and shows a state in which data has been written by passing a write current. [Figure 7] FIG. 7 is a diagram for explaining a method for reading data stored in a magnetoresistive element. [Figure 8] FIG. 8 is a timing chart of signals for writing data to the magnetoresistive element. [Figure 9] FIG. 9 is a cross-sectional view of a magnetoresistive element according to a second embodiment of the present invention. [Figure 10] FIG. 10 is a diagram showing how the magnetoresistive element shown in FIG. 9 is rewritten. [Figure 11] FIG. 11 is a cross-sectional view of a magnetoresistive element according to a third embodiment of the present invention. [Figure 12] FIG. 12 is a diagram showing how the magnetoresistive element shown in FIG. 11 is rewritten. [Figure 13] FIG. 13 is a perspective view schematically showing a magnetoresistive element according to the fourth embodiment. [Figure 14] FIG. 14 is a plan view of the third terminal shown in FIG. [Figure 15] FIG. 15 is a perspective view schematically showing a magnetic memory according to a fifth embodiment of the present invention. [Figure 16] FIG. 16 is a diagram showing an outline of an AI system according to the sixth embodiment of the present invention. [Figure 17] FIG. 17 is a circuit diagram of an example of an AI system using a magnetoresistive element. [Figure 18] FIG. 18 is a diagram showing an outline of an AI system different from that shown in FIG. [Figure 19] FIG. 19 is a plan view of an AI system according to the sixth embodiment of the present invention. [Figure 20] FIG. 20 is a plan view of an AI system according to a sixth embodiment of the present invention, which is different from FIG. [Figure 21A] FIG. 21A is a cross-sectional view of the first sample. [Figure 21B] FIG. 21B is a cross-sectional view of the second sample. [Figure 21C] FIG. 21C is a cross-sectional view of the third sample. [Figure 21D] FIG. 21D is a cross-sectional view of the fourth sample. [Figure 21E]FIG. 21E is a cross-sectional view of the fifth sample. [Figure 21F] FIG. 21F is a cross-sectional view of the sixth sample. [Figure 21G] FIG. 21G is a cross-sectional view of the seventh sample. [Figure 21H] FIG. 21H is a cross-sectional view of the eighth sample. [Figure 21I] FIG. 21I is a cross-sectional view of the prepared comparative sample. [Figure 21J] FIG. 21J is a cross-sectional view of the ninth sample. [Figure 22] FIG. 22 is a diagram showing the dependence of the electrical conductivity of the third sample on the thickness of the heavy metal layer. [Figure 23] FIG. 23 is a diagram showing the dependence of the electrical conductivity of the fourth sample on the thickness of the heavy metal layer. [Figure 24] FIG. 24 is a diagram showing the dependence of the electrical conductivity of the fifth sample on the thickness of the heavy metal layer. [Figure 25] FIG. 25 shows the resistivity results obtained from the thickness dependence of the electrical conductivity of the heavy metal layer in each sample. [Figure 26] FIG. 26 is a graph showing the spin generation efficiency θ SH for each sample. [Figure 27] FIG. 27 shows the spin conductivity σ SH in each sample. [Figure 28] FIG. 28 shows the spin generation efficiency θ SH versus the thickness ratio of the Pt layer to the Ir layer for each sample. [Figure 29] FIG. 29 shows the resistivity ρXX for each thickness ratio of the Pt layer to the Ir layer in each sample. [Figure 30] FIG. 30 shows the spin conductivity σ SH versus the thickness ratio of the Pt layer to the Ir layer in each sample. [Figure 31] FIG. 31 is a diagram showing the dependence of the electrical conductivity of the ninth sample on the thickness of the heavy metal layer. [Figure 32] FIG. 32 is a diagram showing the dependence of electrical conductivity on the thickness of the heavy metal layer. [Figure 33] FIG. 33 shows the results of investigating the interlayer magnetic coupling between the Ir / Pt spacers of the 10th sample. [Figure 34] FIG. 34 is a diagram showing a Hall bar fabricated as the 11th sample and a measurement system. [Figure 35A] FIG. 35A is a cross-sectional view of the eleventh sample produced. [Figure 35B] FIG. 35B is a cross-sectional view of another comparative sample. [Figure 36] FIG. 36 is a graph showing the pulse current dependence of the Hall resistance of the 11th sample and another comparative sample. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. The details of the preferred embodiments of the present invention can be appropriately modified without departing from the scope of the present invention.

[0012] [First embodiment] Fig. 1 is a perspective view schematically showing a magnetoresistive effect element 10 according to a first embodiment of the present invention, and Fig. 2 is a cross-sectional view of the magnetoresistive effect element 10 shown in Fig. 1. The magnetoresistive effect element 10 according to the first embodiment of the present invention includes a heavy metal layer 11, a recording layer 16, a barrier layer 17, and a reference layer 18. The recording layer 16 is arranged on the opposite side of the barrier layer 17 from the reference layer 18, i.e., on the heavy metal layer 11 side, and the reference layer 18 is arranged on the opposite side of the barrier layer 17 from the heavy metal layer 11. The recording layer 16, the barrier layer 17, and the reference layer 18 form a magnetic tunnel junction (MTJ). The magnetoresistive effect element 10 constitutes an MRAM (Magnetic Random Access Memory) element in which the direction of magnetization in the first ferromagnetic layer in the recording layer 16 is reversed using spin orbit torque (SOT) induced magnetization reversal due to a current (referred to as a "write current") flowing through the heavy metal layer 11.

[0013] The heavy metal layer 11 is constructed by laminating an Ir layer 12 and a Pt layer 13. The heavy metal layer 11 is constructed on a substrate 1, which is optionally provided with a buffer layer 2. When the heavy metal layer 11 is constructed by laminating an Ir layer 12 and a Pt layer 13, it is preferable that the outermost of the multiple Pt layers 13, i.e., the Pt layer 13 closest to the recording layer 16 in the lamination direction, forms an interface with the recording layer 16. Providing the Pt layer 13 on the recording layer 16 side of the heavy metal layer 11 reduces the spin-Hall angle θ compared to providing an Ir layer. SH , electrical resistivity ρ, electrical conductivity σ SH This is because either of the above is preferable. The heavy metal layer 11 may be formed by laminating one Ir layer 12 and one Pt layer 13. Even in this case, it is preferable that the Ir layer 12 is provided on the substrate 1 side, and the Pt layer 13 is provided on the recording layer 16 side opposite the substrate 1. Alternatively, as shown in FIGS. 1 and 2, the Ir layer 12 and the Pt layer 13 may be repeatedly laminated. When the Ir layer 12 and the Pt layer 13 are repeatedly laminated multiple times, either the Pt layer 13 or the Ir layer 12 may be on the substrate 1 side or the buffer layer 2 side. In other words, it is sufficient that of the Ir layer 12 and the Pt layer 13 constituting part of the heavy metal layer 11, one layer closest to the recording layer 16 is the Pt layer 13.

[0014] When Ir layers 12 and Pt layers 13 are repeatedly stacked, each Pt layer 13 preferably has a thickness of more than 0.6 nm and not more than 1.5 nm. Each Ir layer 12 preferably has a thickness of 0.6 nm or more and not more than 1.5 nm. Here, the Ir layer 12 is a layer made of Ir (iridium), and the Pt layer 13 is a layer made of Pt (platinum). At least one or two Ir layers 12 and Pt layers 13 are provided, and the number of stacked layers is adjusted so that the entire heavy metal layer 11 is approximately 10 nm or less; for example, six or seven layers is sufficient to pass a current.

[0015] The recording layer 16 includes a first ferromagnetic layer having reversible magnetization and is disposed facing, for example, in contact with, the Pt layer 13, which is the outermost layer of the heavy metal layer 11. The recording layer 16 has a thickness of 0.8 nm to 5.0 nm, preferably 1.0 nm to 3.0 nm. The recording layer 16 may be magnetized in a direction perpendicular to the first ferromagnetic layer. Therefore, the recording layer 16 is configured so that its magnetization can be reversed in a direction perpendicular to the film surface. Note that "magnetized in a perpendicular direction" also means that the recording layer 16 may have a magnetization component parallel to the film surface. The recording layer 16 may be magnetized in an in-plane direction relative to the first ferromagnetic layer. Therefore, the recording layer 16 is configured so that its magnetization can be reversed in an in-plane direction relative to the film surface. Note that "magnetized in an in-plane direction" also means that the recording layer 16 may have a magnetization component perpendicular to the film surface. In order to generate interface magnetic anisotropy in the recording layer 16, the recording layer 16, i.e., the first ferromagnetic layer, is made of CoFeB, FeB, CoB, etc. When shape magnetic anisotropy is used in the fine MTJ region, CoFeB, FeB, or CoB may be processed to have the longest length in the film thickness direction, and a single layer of this may be used as the recording layer.

[0016] The barrier layer 17 is formed facing the first ferromagnetic layer of the recording layer 16. The barrier layer 17 is preferably formed of an insulating material such as MgO, Al2O3, AlN, or MgAlO, especially MgO. The barrier layer 17 has a thickness of 0.1 nm to 2.5 nm, preferably 0.5 nm to 1.5 nm.

[0017] The reference layer 18 may be configured as a single layer as shown in FIGS. 1 and 2, or may have a three-layer laminated ferrimagnetic structure, for example, in which a ferromagnetic layer, a non-magnetic layer, and a ferromagnetic layer are stacked in this order. In this case, the magnetization direction of one ferromagnetic layer is antiparallel to that of the other ferromagnetic layer. When the recording layer 16 is magnetized perpendicularly, the magnetization of one ferromagnetic layer is oriented in the −z direction, and the magnetization of the other ferromagnetic layer is oriented in the +z direction. When the recording layer 16 is magnetized in the in-plane direction, the magnetization of one ferromagnetic layer is oriented, for example, in the −x direction, and the magnetization of the other ferromagnetic layer is oriented in the +x direction. The magnetization directions of the one ferromagnetic layer and the other ferromagnetic layer may be in the xy plane.

[0018] The material and thickness of the second ferromagnetic layer of reference layer 18 closest to barrier layer 17 are selected so that interfacial magnetic anisotropy occurs at the interface between barrier layer 17 and the second ferromagnetic layer of reference layer 18 closest to barrier layer 17. By providing reference layer 18 with a laminated ferrimagnetic structure and antiferromagnetically coupling the magnetization of one ferromagnetic layer of reference layer 18 with the magnetization of the other ferromagnetic layer, the magnetization of one ferromagnetic layer of reference layer 18 and the magnetization of the other ferromagnetic layer are pinned in the perpendicular direction or in-plane direction. The magnetization of one ferromagnetic layer of reference layer 18 and the magnetization of the other ferromagnetic layer may also be antiferromagnetically coupled by interlayer interaction to pin the magnetization direction. The second ferromagnetic layer of reference layer 18 and the like are made of the same material as the ferromagnetic material constituting recording layer 16.

[0019] Here, as shown in Figure 1, the recording layer 16, the barrier layer 17, and the reference layer 18 have a cylindrical shape, and the shapes of the recording layer 16, the barrier layer 17, and the reference layer 18 when viewed in the stacking direction of the heavy metal layer 11, i.e., the shapes when viewed in a plan view, are symmetrical with respect to a line passing through the center of the circle, i.e., are symmetrical with respect to any line in the direction in which the write current flows in the heavy metal layer 11.

[0020] Capping layer 19 is a layer of about 1.0 nm made of a conductive material such as Ta to prevent oxidation, and may be formed adjacent to reference layer 18. Capping layer 19 may also be made of a non-magnetic layer such as MgO, and a tunnel current flows through capping layer 19, causing a current to flow from third terminal T3 to reference layer 18.

[0021] A first terminal T1 and a second terminal T2 are provided either above or below the heavy metal layer 11, or one facing downward and the other facing upward, sandwiching an MTJ consisting of a recording layer 16, a barrier layer 17, and a reference layer 18. In the example shown, the first terminal T1 is provided on the heavy metal layer 11, and the second terminal T2 is provided on the heavy metal layer 11 on the opposite side to the first terminal T1, sandwiching the MTJ consisting of the recording layer 16, the barrier layer 17, and the reference layer 18. The first terminal T1 is connected to either the source or the drain of a FET-type first transistor Tr1, and the other of the source or the drain of the first transistor Tr1 is connected to a first bit line, and a write voltage V w The first terminal T1 is connected to a power supply (write power supply) that supplies a write current Iw, and the gate of the first FET transistor Tr1 is connected to the word line. The second terminal T2 is connected to, for example, ground. In this case, a second FET transistor Tr2 may be interposed. The second terminal T2 may be connected to a second bit line via the second transistor Tr2, and the direction of the write current Iw may be changed depending on the potential difference between the first terminal T1 and the second terminal T2. For example, the first bit line is set to a high level, the second bit line is set to a low level, and the write current Iw is passed from the first terminal T1 to the second terminal T2. Conversely, the first bit line is set to a low level, the second bit line is set to a high level, and the write current Iw is passed from the second terminal T2 to the first terminal T1. During read, the second transistor Tr2 is turned off to prevent the read current from flowing to the second terminal T2.

[0022] The third terminal T3 is provided on the cap layer 19 and in contact with the cap layer 19. The third terminal T3 has the same cylindrical shape as the recording layer 16, the barrier layer 17, and the reference layer 18, and is disposed on the upper surface of the cap layer 19, covering the entire upper surface, and is electrically connected to the reference layer 18 via the cap layer 19. The third terminal T3 is connected to either the source or the drain of a third FET transistor Tr3, the other of which is connected to a third bit line, and a read voltage V Read The gate of the third transistor Tr3 is connected to a power supply (read power supply) that supplies a read voltage line. By turning off the second transistor Tr2, it is possible to prevent current from flowing to the second terminal T2.

[0023] A method of writing to the magnetoresistive element 10 shown in Fig. 1 will be described. In the magnetoresistive element 10, the resistance of the MTJ changes depending on whether the magnetization directions of the first ferromagnetic layer and the second ferromagnetic layer of the recording layer 16 and the reference layer 18, which are adjacent to each other with a barrier layer 17 interposed therebetween, are parallel or antiparallel. Therefore, one bit of data, "0" or "1," is assigned depending on whether the magnetization directions are parallel or antiparallel, and data is stored in the magnetoresistive element 10.

[0024] A specific description will be given below. First, a case will be described in which data "0" is written to the magnetoresistive element 10 that stores data "1". In the initial state, as shown in FIG. 3, the magnetoresistive element 10 stores data "1", the direction of the magnetization M11 of the recording layer 16 is upward, the direction of the magnetization M12 of the reference layer 18 is downward, and the directions of the magnetization M11 and the magnetization M12 are antiparallel. It is assumed that the first transistor Tr1 and the third transistor Tr3 are off. An external magnetic field H0 is applied in the +x direction. In this state, the first transistor Tr1 is turned on, and a write voltage V is applied to the first terminal T1. w Then, the write voltage V w is set higher than the ground voltage, a write current I flows from the first terminal T1 to the second terminal T2 via the heavy metal layer 11.w flows from one end of the heavy metal layer 11 to the other end in the +x direction. w At this time, since the third transistor Tr3 is off, no current flows from the first terminal T1 to the third terminal T3 via the MTJ. w is a pulse current, so by adjusting the time that the first transistor Tr1 is in the on state, the write current I w The pulse width of the write current I w When the magnetic flux flows through the heavy metal layer 11, a spin current (flow of spin angular motion) is generated within the heavy metal layer 11 due to the spin Hall effect caused by spin-orbit interaction, and spins of opposite directions flow in the corresponding ±z directions of the heavy metal layer 11, resulting in uneven distribution of spin within the heavy metal layer 11. Then, the spin current flowing through the heavy metal layer 11 causes spins oriented in one direction to be absorbed into the recording layer 16. In the first ferromagnetic layer of the recording layer 16, the absorbed spins exert a torque on the magnetization M11, which rotates the magnetization M11, causing the upward magnetization M11 to reverse and become downward, and the directions of the magnetization M11 and the magnetization M12 become parallel. For example, by applying an external magnetic field H0 in the +x direction, the torque due to the spin is canceled out, and the magnetization M11 becomes oriented in the -z direction. After that, the first transistor Tr1 is turned off, and the write current I w By stopping the magnetization, the magnetization M11 is fixed in the -z direction, and data "0" is stored. This state is shown in Figure 4.

[0025] Next, a case where data "1" is written to the magnetoresistive element 10 that stores data "0" will be described. In the initial state, as shown in FIG. 5, the magnetoresistive element 10 stores data "0", the direction of the magnetization M11 of the recording layer 16 is downward, the direction of the magnetization M12 of the reference layer 18 is downward, and the directions of the magnetization M11 and the magnetization M12 are parallel to each other. The first transistor Tr1 and the third transistor Tr3 are assumed to be turned off. An external magnetic field H0 is applied in the +x direction. In this state, the first transistor Tr1 is turned on, and a write voltage V is applied to the first terminal T1. w Then, the write voltage V wis set lower than the ground voltage, the write current I flows from the second terminal T2 to the first terminal T1 via the heavy metal layer 11. w flows from the other end of the heavy metal layer 11 to one end in the −x direction, and a write current I w At this time, since the third transistor Tr3 is off, no current flows from the second terminal T2 to the third terminal T3 via the MTJ. w is a pulse current, so by adjusting the time that the first transistor Tr1 is in the on state, the write current I w The pulse width of the write current I w When the magnetic flux flows through the heavy metal layer 11, a spin current (flow of spin angular motion) is generated within the heavy metal layer 11 due to the spin Hall effect caused by spin-orbit interaction, and spins of opposite directions flow in the corresponding ±z directions of the heavy metal layer 11, resulting in uneven distribution of spin within the heavy metal layer 11. Then, due to the spin current flowing through the heavy metal layer 11, spins pointing in one direction flow into the recording layer 16. In the first ferromagnetic layer of the recording layer 16, the flowing spins exert a torque on the magnetization M11, which rotates the magnetization M11, causing the downward magnetization M11 to reverse and become upward, and the directions of the magnetization M11 and the magnetization M12 become antiparallel. For example, by applying an external magnetic field H0 in the +x direction, the torque due to the spin is canceled out, and the magnetization M11 becomes oriented in the +z direction. After that, the first transistor Tr1 is turned off, and the write current I w By stopping the write current I, the magnetization M11 is fixed in the +z direction, and data “1” is stored. w By passing a current through the recording layer 16, the magnetization of the recording layer 16 is reversed, and data is rewritten. This state is shown in FIG.

[0026] Therefore, in the magnetoresistive element 10, a write current I w By passing a current through the recording layer 16, the magnetization direction of the recording layer 16 can be reversed, and data "0" or data "1" can be written.

[0027] In addition, the magnetoresistive effect element 10 may apply a voltage between one end (first terminal T1) and the other end (second terminal T2) of the heavy metal layer 11 to pass a write current through the heavy metal layer 11, and may also apply a voltage to the MTJ via the third terminal T3 to reduce the magnetic anisotropy of the ferromagnetic layer of the recording layer 16, thereby reversing the magnetization M11 of the recording layer 16 by the spins injected from the heavy metal layer 11.

[0028] Next, a data read method will be described with reference to FIG. 7. It is assumed that the first and third transistors Tr1 and Tr3 are turned off. First, the write voltage V w Read out the voltage V Read Next, the read operation is performed by turning on the first transistor Tr1 and the third transistor Tr3, and applying the write voltage V to the first terminal T1. w and a read voltage V is applied to the third terminal T3. Read Apply the write voltage V w is the read voltage V Read Since the read current I flows from the first terminal T1 to the heavy metal layer 11, the recording layer 16, the barrier layer 17, the reference layer 18, the cap layer 19, and the third terminal T3 in this order. r The read current I r flows through the barrier layer 17. The read current I r is detected by a detector (not shown). r Since the magnitude of changes depending on the resistance value of the MTJ, the read current I r From the magnitude of the read current I, it can be determined whether the MTJ is in a parallel or antiparallel state, i.e., whether the MTJ is storing data "0" or data "1." r is a pulse current, and the pulse width is adjusted by adjusting the time when the third transistor Tr3 is turned on.

[0029] Here, the read current I r is the read current I r flows through the MTJ, the read current I rIt is desirable to set the current to a value weak enough that the spin transfer magnetization of the recording layer 16 is not reversed by the write voltage V w and read voltage V Read By adjusting the potential difference appropriately, the read current I r Also, the first transistor Tr1 is turned on to adjust the magnitude of the write voltage V w is turned on, and then the third transistor Tr3 is turned on to generate the read voltage V Read It is desirable to turn on the transistor T1 because this can prevent current from flowing from the third terminal T3 to the second terminal T2 via the MTJ, thereby preventing current other than the read current from flowing through the MTJ.

[0030] Then, after the third transistor Tr3 is turned off, the first transistor Tr1 is turned off. By turning off the first transistor Tr1 after the third transistor Tr3, the write voltage V w Read out the voltage V Read By turning it off later, the read voltage V Read Therefore, the magnetoresistive element 10 can protect the barrier layer 17, further reduce the thickness of the barrier layer 17, and also suppress read disturbance, which occurs when the magnetization state of the recording layer 16 changes due to a current flowing through the MTJ.

[0031] Another method of writing to the magnetoresistive effect element 10 according to the first embodiment will now be described. For the purpose of describing the case where the method is applied to an artificial intelligence system, which will be described later, it is assumed that a plurality of recording layers 16, barrier layers 17, and reference layers 18 are provided as MTJs on the same heavy metal layers 11a, 11b, and 11c, as shown in FIG. 15, which will be described later. In the initial state, the first transistor Tr1 connected to the first terminal T1 of the heavy metal layer 11 and the third transistor Tr3 connected to the third terminal T3 of each MTJ are all off. If necessary, the third transistor Tr3 connected to the third terminal T3 is turned on to reduce the magnetic anisotropy of the recording layer 16. The write voltage Vw is set to a positive voltage, the first transistor Tr1 connected to the first terminal T1 is turned on, and the write current I w is passed from the first terminal T1 to the second terminal T2. As a result, since the magnetic anisotropy constant of the MTJ is small, the recording layer 16 having perpendicular magnetization rotates and the axis of easy magnetization is not determined in a stable direction. Next, the third transistors Tr3 connected to the third terminal T3 in each MTJ are all turned on to pass the write auxiliary current I WA is passed, and only the portions where it is passed are written. After that, all third transistors Tr3 connected to the third terminal T3 in each MTJ are turned off, and the first transistor Tr1 connected to the first terminal T1 is turned off.

[0032] Next, the write voltage V w is set to a negative voltage, the first transistor Tr1 connected to the first terminal T1 is turned on, and a write current I w When the magnetic anisotropy constant Δ of the recording layer 16 is set to a value between 5 and 15, the write current I w When the write auxiliary current I flows, the recording layer 16 having perpendicular magnetization rotates, and the axis of easy magnetization is not determined in a stable direction. After that, the third transistor Tr3 connected to the third terminal T3 of the MTJ to which data "1" is to be written is turned on to select the MTJ to be written, and the write auxiliary current I WA When the write assist current I flows, the recording layer 16 having perpendicular magnetization WA When this element is used as a cross-point memory of a crossbar network, the magnetic anisotropy constant Δ of the recording layer 16 is set to a value between 5 and 15, and the write current I w When current flows, the recording layer 16, which has perpendicular magnetization, rotates and the axis of easy magnetization is not fixed in a stable direction, but this is written using wiring for applying a magnetic field, which will be described later.In this case, since the magnetic anisotropy constant Δ of the recording layer 16 is small, at 5 to 15, it is possible to write with a small current magnetic field.

[0033] FIG. 8 is a timing chart of a signal for writing data to the magnetoresistive element.w and write auxiliary current I WA is a pulsed current. As shown in Figure 8, the write current I w pulse and write auxiliary current I WA The pulses of the write current I w The pulse turns on first, and the write current I w Before the pulse is turned off, the write auxiliary current I WA After this, the write current I w The pulse is turned off, and the write auxiliary current I WA The pulse is turned off.

[0034] Alternatively, data "1" may be written to all MTJs at once, and then data "0" may be written to only the selected MTJ. In addition, the read operation is performed by turning on the first transistor Tr1 connected to the first terminal T1, and then turning on the third transistor Tr3 connected to the third terminal T3 of the MTJ to be read, and supplying a read current I r The readout method is the same as in the first embodiment.

[0035] The magnetoresistive effect element 10 according to the first embodiment of the present invention comprises a heavy metal layer 11 formed by stacking an Ir layer 12 and a Pt layer 13, a recording layer 16 facing the heavy metal layer 11 and preferably located on the side of one of the Pt layers 13, which is the uppermost layer of the heavy metal layer 11, and including a first ferromagnetic layer having reversible magnetization, a reference layer 18 including a second ferromagnetic layer whose magnetization direction is fixed, and a barrier layer 17 sandwiched between the first and second ferromagnetic layers and made of an insulator. Therefore, the direction of magnetization in the first ferromagnetic layer in the recording layer 16 can be efficiently reversed with low resistance by a write current flowing through the heavy metal layer 11 without reducing the reversal efficiency.

[0036] It is also possible to eliminate the need for an external magnetic field by adjusting the shapes of recording layer 16, barrier layer 17, and reference layer 18 in a planar view, or by adjusting the spin directions in recording layer 16 and reference layer 18. The magnetization directions of recording layer 16 and reference layer 18 may be either in-plane parallel or in-plane perpendicular.

[0037] (Second embodiment) FIG. 9 is a cross-sectional view of a magnetoresistive effect element 30 according to a second embodiment of the present invention. In the second embodiment, as shown in FIG. 9, the heavy metal layer 11 is configured by laminating one Ir layer 12 and one Pt layer 13, with one ferromagnetic layer 14 and the other ferromagnetic layer 15 provided on either side of the heavy metal layer 11. The magnetization M21 of the one ferromagnetic layer 14 and the magnetization M22 of the other ferromagnetic layer 15 are opposite in direction. That is, in a configuration in which a buffer layer 2 is optionally provided on a substrate 1 and a heavy metal layer 11 is provided thereon, one ferromagnetic layer 14 is provided on the substrate 1 or buffer layer 2 side of the heavy metal layer 11, and the other ferromagnetic layer 15 is provided on the recording layer 16 side. The reason for the Ir layer 12 and the Pt layer 13 being one layer each is that one ferromagnetic layer 14 and the other ferromagnetic layer 15 are antiferromagnetically coupled.

[0038] In the second embodiment, when one ferromagnetic layer 14 and the other ferromagnetic layer 15 are both perpendicular magnetization layers made of Co or the like, it is preferable that recording layer 16 and reference layer 18 are also perpendicular magnetization layers.

[0039] In the second embodiment, when a current is passed through the stacked portion of the heavy metal layer 11, particularly the Ir layer 12 and the Pt layer 13, between the one ferromagnetic layer 14 and the other ferromagnetic layer 15, the magnetizations of the one ferromagnetic layer 14 and the other ferromagnetic layer 15 are reversed due to the spin Hall effect, and the magnetization of the recording layer 16 is reversed due to the influence of the magnetization reversal of the one ferromagnetic layer 14 and the other ferromagnetic layer 15. As shown on the left side of FIG. 10, a write current I w By passing a write current I in the −x direction, the magnetization M21 of one ferromagnetic layer 14 and the magnetization M22 of the other ferromagnetic layer 15 are reversed, and the direction of the magnetization M11 of the recording layer 16 is reversed.w By passing a current through the ferromagnetic layer 14, the magnetization M21 of the ferromagnetic layer 14 and the magnetization M22 of the other ferromagnetic layer 15 are reversed, and as a result, the direction of the magnetization M11 of the recording layer 16 is reversed, as shown on the right side of FIG.

[0040] Here, the preferred thicknesses of the Ir layer 12 and the Pt layer 13 of the heavy metal layer 11 will be explained. For example, if both the first ferromagnetic layer 14 and the second ferromagnetic layer 15 are made of Co, the Pt layer 13 is preferably 0.6 nm to 1.0 nm thick. In this case, the Ir layer 12 should be 0.45 nm to 0.65 nm, or 1.3 nm to 1.5 nm thick. This is because the first ferromagnetic layer 14 and the second ferromagnetic layer 15 are antiferromagnetically coupled. The first ferromagnetic layer 14 and the second ferromagnetic layer 15 are both preferably 1 nm or less.

[0041] The magnetoresistive effect element 30 according to the second embodiment comprises a heavy metal layer 11 formed by laminating an Ir layer 12 and a Pt layer 13 one on top of the other, and further laminating one ferromagnetic layer 14 and the other ferromagnetic layer 15 above and below the heavy metal layer 11; a recording layer 16 including a first ferromagnetic layer having reversible magnetization, which is disposed opposite the heavy metal layer 11 on the Pt layer 13 side with the other ferromagnetic layer 15 interposed therebetween; a reference layer 18 including a second ferromagnetic layer whose magnetization direction is fixed; and a barrier layer 17 sandwiched between the first and second ferromagnetic layers and made of an insulator. Therefore, a write current flowing through the heavy metal layer 11 efficiently reverses the magnetization directions of both the upper and lower ferromagnetic layers 14 and the other ferromagnetic layer 15 in the heavy metal layer 11 with low resistance and without reducing reversal efficiency, thereby reversing the magnetization direction of the first ferromagnetic layer in the recording layer 16.

[0042] 9 and 10, a first non-magnetic layer 20 is provided between heavy metal layer 11 and recording layer 16, dividing the crystal structures of heavy metal layer 11 and recording layer 16. A second non-magnetic layer 21 is provided on the opposite side of the second ferromagnetic layer of reference layer 18 adjacent to barrier layer 17 from barrier layer 17, dividing the crystal structures of the layers above and below second non-magnetic layer 21. The first non-magnetic layer 20 and second non-magnetic layer 21 contain one or more elements selected from W, Ta, Mo, Hf, etc.

[0043] As shown in FIG. 9, on the opposite side of the second ferromagnetic layer across the second nonmagnetic layer 21, for example, (Co / Pt) n / Ir / (Co / Pt) m The pinned layer 22 is provided to fix and pin the direction of the magnetization M12 of the second ferromagnetic layer of the reference layer 18. In such a case, the second ferromagnetic layer and the pinned layer 22 may be collectively referred to as the reference layer. The above m and n are any natural numbers.

[0044] (Third embodiment) FIG. 11 is a cross-sectional view of a magnetoresistive effect element 30 according to a third embodiment of the present invention. Similar to the second embodiment, the third embodiment also includes a heavy metal layer 11 formed by stacking one Ir layer 12 and one Pt layer 13. One ferromagnetic layer 14 and another ferromagnetic layer 15 are provided on either side of the heavy metal layer 11. The magnetization M21 of the one ferromagnetic layer 14 and the magnetization M22 of the other ferromagnetic layer 15 are opposite in direction. Specifically, in a configuration in which a buffer layer 2 is optionally provided on a substrate 1 and a heavy metal layer 11 is provided thereon, one ferromagnetic layer 14 is provided on the substrate 1 or buffer layer 2 side of the heavy metal layer 11, and the other ferromagnetic layer 15 is provided on the recording layer 16 side. The reason for the presence of one Ir layer 12 and one Pt layer 13 is that one ferromagnetic layer 14 and another ferromagnetic layer 15 are antiferromagnetically coupled.

[0045] In the third embodiment, when one ferromagnetic layer 14 and the other ferromagnetic layer 15 are both horizontally magnetized layers such as CoFeB, it is preferable that recording layer 16 and reference layer 18 are also horizontally magnetized layers.

[0046] In the third embodiment, when a current is passed through the stacked portion of the heavy metal layer 11, particularly the Ir layer 12 and the Pt layer 13, between the one ferromagnetic layer 14 and the other ferromagnetic layer 15, the magnetizations of the one ferromagnetic layer 14 and the other ferromagnetic layer 15 are reversed due to the spin Hall effect, and the magnetization of the recording layer 16 is reversed due to the influence of the magnetization reversal of the one ferromagnetic layer 14 and the other ferromagnetic layer 15. As shown on the left side of FIG. 12, a write current I w By passing a write current I in the −x direction, the magnetization M21 of one ferromagnetic layer 14 and the magnetization M22 of the other ferromagnetic layer 15 are reversed, and the direction of the magnetization M11 of the recording layer 16 is reversed. w By passing a current through the ferromagnetic layer 14, the magnetization M21 of the ferromagnetic layer 14 and the magnetization M22 of the other ferromagnetic layer 15 are reversed, and as a result, the direction of the magnetization M11 of the recording layer 16 is reversed, as shown on the right side of FIG.

[0047] Here, the preferred thicknesses of the Ir layer 12 and the Pt layer 13 of the heavy metal layer 11 are the same as those in the second embodiment. As illustrated in FIG. 11, on the opposite side of the second ferromagnetic layer with the second nonmagnetic layer 21 interposed therebetween, for example, (Co / Pt) n / Ir / (Co / Pt) m The pinned layer 22 is provided to fix and pin the direction of the magnetization M12 of the second ferromagnetic layer of the reference layer 18. In such a case, the second ferromagnetic layer and the pinned layer 22 may be collectively referred to as the reference layer. The above m and n are any natural numbers.

[0048] The magnetoresistive effect element 30 of the third embodiment comprises a heavy metal layer 11 formed by laminating an Ir layer 12 and a Pt layer 13 one by one, and further laminating one ferromagnetic layer 14 and the other ferromagnetic layer 15 above and below the heavy metal layer 11; a recording layer 16 including a first ferromagnetic layer having reversible magnetization, which is provided on the Pt layer 13 side facing the heavy metal layer 11 with another ferromagnetic layer 15 interposed therebetween; a reference layer 18 including a second ferromagnetic layer whose magnetization direction is fixed; and a barrier layer 17 sandwiched between the first and second ferromagnetic layers and made of an insulator. Therefore, a write current flowing through the heavy metal layer 11 efficiently reverses the magnetization directions of one ferromagnetic layer 14 and the other ferromagnetic layer 15 above and below the heavy metal layer 11 with low resistance and without reducing reversal efficiency, thereby reversing the magnetization direction of the first ferromagnetic layer in the recording layer 16.

[0049] [Fourth embodiment] FIG. 13 is a perspective view schematically illustrating a magnetoresistive effect element 50 according to the fourth embodiment. FIG. 14 is a plan view of the third terminal T3 shown in FIG. 13. The magnetoresistive effect element 50 according to the fourth embodiment differs from the magnetoresistive effect element 10 according to the first embodiment in the following respects. Specifically, the recording layer 16, the barrier layer 17, and the reference layer 18 are not cylindrical, but have a notch portion NA cut out at a plane 5 inclined to the x-axis and y-axis and extending along the z-axis. Thus, the shapes of the recording layer 16, the barrier layer 17, and the reference layer 18 as viewed in the stacking direction of the heavy metal layer 11, i.e., their shapes in a planar view, are asymmetric with respect to a line in the direction of the write current flow in the heavy metal layer 11. The provision of the notch portion NA determines the direction in which precession is likely to occur. The magnetization direction of the recording layer 16 can be reversed and maintained without applying an external magnetic field. The materials and thicknesses of the recording layer 16, barrier layer 17, reference layer 18, cap layer 19, terminals, etc. that constitute the MTJ are the same as those in the first embodiment. This is also applicable to the second and third embodiments as well as the first embodiment.

[0050] [Fifth embodiment] A magnetic memory 60 according to a fifth embodiment of the present invention will be described in detail. FIG. 15 is a perspective view schematically illustrating the magnetic memory 60 according to the fifth embodiment of the present invention. Unlike the first to fourth embodiments, the magnetic memory 60 according to the fifth embodiment is configured by arranging a plurality of magnetoresistive effect elements in an array on either the top or bottom of the same heavy metal layer 11a, i.e., on the heavy metal layers 11a, 11b, and 11c in the illustrated embodiment. As shown in FIG. 15, a plurality of magnetoresistive effect elements, for example, five magnetoresistive effect elements M11, M12, M13, M14, and M15, are arranged on one heavy metal layer 11a to form one unit 61. Each of the magnetoresistive effect elements M11 to M15 is configured by stacking a recording layer 16, a barrier layer 17, a reference layer 18, a cap layer 19, and a terminal in this order. Each unit 61 has a first common terminal (not shown) and a second common terminal (not shown) sandwiched between multiple magnetoresistive effect elements M11 to M15 on the heavy metal layer 11, with either the source or the drain of a first transistor Tr11 connected to the first common terminal so that a write voltage can be applied, and either the source or the drain of a second transistor Tr12 connected to the second common terminal, which is connected to ground, for example.

[0051] In the magnetic memory 60 according to the fifth embodiment of the present invention, each of the magnetoresistive elements M11, M12, M13, M14, and M15 includes a heavy metal layer 11a, a recording layer 16, a barrier layer 17, and a reference layer 18, as described in the first embodiment with reference to FIGS. 1 and 2. The recording layer 16 is disposed on the opposite side of the barrier layer 17 from the reference layer 18, i.e., on the heavy metal layer 11a side, and the reference layer 18 is disposed on the opposite side of the barrier layer 17 from the heavy metal layer 11a. The recording layer 16, the barrier layer 17, and the reference layer 18 form a magnetic tunnel junction (MTJ). In the magnetoresistive elements M11, M12, M13, M14, and M15, the direction of magnetization in the first ferromagnetic layer in the recording layer 16 is reversed by a current (referred to as a "write current") flowing through the heavy metal layer 11a using spin-orbit torque-induced magnetization reversal. As in the first embodiment, the recording layer 16, the barrier layer 17, and the reference layer 18 have a cylindrical shape to match the shape of the recording layer 16, and are symmetrical about the direction of view (z direction) in a plan view. That is, the recording layer 16, the barrier layer 17, and the reference layer 18 are symmetrical about a line in the direction of the current flowing through the heavy metal layer 11a. This also applies to units 62 and 63, which will be described later.

[0052] Furthermore, as shown in FIG. 15, the magnetic memory 60 according to the fifth embodiment has a plurality of elements, for example, five magnetoresistance effect elements M21, M22, M23, M24, and M25, arranged on one heavy metal layer 11b to form one unit 62, and a plurality of elements, for example, five magnetoresistance effect elements M31, M32, M33, M34, and M35, arranged on one heavy metal layer 11c to form one unit 63, and each of the magnetoresistance effect elements M21 to M25, M31 to M35 is formed by stacking a recording layer 16, a barrier layer 17, a reference layer 18, a cap layer 19, and a terminal in that order. Each unit 62, 63 has a first common terminal (not shown) and a second common terminal (not shown) for the corresponding heavy metal layer 11b, 11c, sandwiching a plurality of magnetoresistive effect elements M21 to M25, M31 to M35. The first common terminal is connected to either the source or the drain of the first transistor Tr21, Tr31 so that a write voltage can be applied thereto. The second common terminal is connected to either the source or the drain of the second transistor Tr22, Tr32, and is connected to, for example, ground. The magnetic memory 60 is configured by arranging the units 61, 62, and 63. The fifth embodiment relates to an array of 5 × 3 magnetoresistive effect elements as shown, but is not limited thereto and can be applied to an array integrating m × n magnetoresistive effect elements.

[0053] The magnetic memory 60 according to the fifth embodiment includes a write unit (not shown) having a write power supply for writing data to the magnetoresistive elements M11 to M35. The write unit supplies a write current I w By passing a current, data is written to the magnetoresistive elements M11 to M35.

[0054] The magnetic memory 60 includes a read power supply and a current detector (neither of which are shown), and a read unit that reads data from the magnetoresistive elements M11 to M35. The read power supply supplies a read current I r The current detector detects a read current I r is detected, and the data written in the magnetoresistive elements M11 to M35 is read out.

[0055] A method for writing data to the magnetoresistive effect elements M11 to M35 will be described. The case where the second common terminals T12, T22, and T32 of the heavy metal layers 11a, 11b, and 11c are connected to ground will be described. However, they may also be connected to ground via second transistors Tr12, Tr22, and Tr32. In the initial state, the first transistors Tr11, Tr21, and Tr31 connected to the first common terminals T11, T21, and T31 of the heavy metal layers 11a, 11b, and 11c, and the third transistors Tr131 to Tr135, Tr231 to Tr235, and Tr331 to Tr335 connected to the third terminals T131 to T135, T231 to T235, and T331 to T335 of each MTJ, are all off. First, the third transistors Tr131 to Tr135, Tr231 to Tr235, and Tr331 to Tr335 connected to the third terminals T131 to T135, T231 to T235, and T331 to T335 of each MTJ are all turned on to reduce the magnetic anisotropy of the recording layer 16 of each MTJ. w is set to a positive voltage, the first transistors Tr11, Tr21, and Tr31 connected to the first common terminals T11, T21, and T31 are turned on, and the write current I w is sent from the first common terminals T11, T21, and T31 to the second common terminals T12, T22, and T32. This causes data "0" to be written to all of the MTJs at once. After that, the third transistors Tr131 to Tr135, Tr231 to Tr235, and Tr331 to Tr335 connected to the third terminals T131 to T135, T231 to T235, and T331 to T335 of each MTJ are all turned off, and the first transistors Tr11, Tr21, and Tr31 connected to the first common terminals T11, T21, and T31 are turned off.

[0056] Next, the third transistor Tr131 connected to the third terminal (for example, T131) of the MTJ into which data “1” is to be written is turned on to select the MTJ to be written. Then, the write voltage V wis set to a negative voltage, the first transistor Tr11 connected to the first common terminal T11 is turned on, and a write current I is supplied from the second common terminal T12 to the first common terminal T11. w is passed through the MTJ. Since the magnetic anisotropy of the recording layer 16 is small only in the MTJ in which the third transistor Tr131 connected to the third terminal T131 is turned on, the magnetization is reversed. As a result, data "1" is written only in the selected MTJ. After that, the third transistor (Tr131 in this case) that is turned on is turned off, and the first transistor Tr11 connected to the first common terminal T11 is turned off, thereby completing the write operation.

[0057] Alternatively, data "1" may be written to all MTJs at once, and then data "0" may be written to only the selected MTJ. In addition, the read operation is performed by turning on the first transistor Tr11 connected to the first common terminal (e.g., T11) of the MTJ to be read, and then turning on the third transistor Tr132 connected to the third terminal (e.g., T132) of the MTJ to be read, and supplying a read current I r The subsequent read operation is the same as in the first embodiment.

[0058] The magnetic memory 60 according to the fifth embodiment of the present invention comprises a recording layer 16 including a first ferromagnetic layer having reversible magnetization, which is formed by stacking an Ir layer 12 and a Pt layer 13 and is disposed opposite a heavy metal layer 11 with a ferromagnetic layer 15 interposed therebetween; a reference layer 18 including a second ferromagnetic layer whose magnetization direction is fixed; and a barrier layer 17 sandwiched between the first and second ferromagnetic layers and made of an insulator. Therefore, a write current flowing through the heavy metal layer 11 efficiently reverses the magnetization direction of one of the ferromagnetic layers 14 and the other ferromagnetic layer 15 above and below the heavy metal layer 11 with low resistance and without reducing reversal efficiency, thereby reversing the magnetization direction in the first ferromagnetic layer.

[0059] In particular, by reducing the resistivity of the heavy metal layers 11a, 11b, and 11c, the voltage drop due to the wiring resistance between the first common terminals T11, T21, and T31 and the corresponding second common terminals T21, T22, and T23 is reduced, and the voltages applied to the MTJs provided above or below the same heavy metal layer 11a, 11b, and 11c become approximately the same. This also reduces the restriction on the number of magnetoresistance effect elements provided on the same heavy metal layer, increasing the degree of freedom in design.

[0060] In the fifth embodiment, as described above, not only can a plurality of magnetoresistive effect elements according to the first embodiment be provided on the same heavy metal layer 11a, 11b, and 11c, but also, as in the second and third embodiments, heavy metal layer 11 can be configured by providing a stack of Ir layer 12 and Pt layer 13 between one ferromagnetic layer 14 and the other ferromagnetic layer 15, and a plurality of magnetoresistive effect elements each consisting of a recording layer 16, a barrier layer 17, and a reference layer 18 can be provided on the same heavy metal layer 11a, 11b, and 11c. Furthermore, the MTJ need not only be cylindrical, but may also have a notch NA as in the fourth embodiment.

[0061] [Sixth embodiment] FIG. 16 is a diagram showing an outline of an AI system according to a sixth embodiment of the present invention. A plurality of first wirings (S1, . . . , S n ) and a plurality of second wirings (B1, . . . , B m ), and the first wiring (S1, . . . , S n ) and the second wiring (B1,...,B m ) and the first wiring (S1,...,S n ) and the second wiring (B1,...,B m ) and the crosspoint memory (CM 11 ,···,CM mn ) is provided. Crosspoint memory (CM 11 ,···,CM mn) is composed of memory elements such as ReRAM (resistive random access memory), PCM (phase change memory), MTJ, etc. In this way, a resistive crossbar network is provided.

[0062] The first wiring (S1, ,S n ) is connected to an input line INPUT, and the other end is connected to electronic neurons (NR1,...,NR n ) are connected to the electronic neurons (NR1,...,NR n ) is a neuronal substrate (SA NR1 ,···,SA NRn ) is formed on the neuronal substrate (SA NR1 ,···,SA NRn ) is composed of a laminate of a substrate 1, a buffer layer 2, and a heavy metal layer 11. n ) has the same configuration as the magnetoresistive effect elements according to the first to fourth embodiments of the present invention. NR1 ,···,SA NRn ) is connected to the output line OUTPUT.

[0063] The magnetoresistive effect elements 10 according to the first to fourth embodiments of the present invention are used as electronic neurons (NR1, . . . , NR n ) and electronic neurons (NR1,...,NR n The weighted sum of the resistive crossbar network is input to the crosspoint memory (CM). The artificial intelligence (AI) system is configured such that the resistive crossbar network is one stage, and multiple stages are connected, with the output of the resistive crossbar network of the previous stage being input to the resistive crossbar network of the next stage. 11 ,···,CM mn ) corresponds to the synapse in an AI system.

[0064] Crosspoint Memory (CM 11 ,···,CM mn) stores data in a pair of memories corresponding to a pair of second wirings. For example, when an input is received from the previous stage resistive crossbar network, VS is input to the second wiring B1 in response to the input, and -VS is input to the second wiring B2. In response to this, the crosspoint memory CM 11 and crosspoint memory CM 21 The data is stored in the cross point memory CM. 31 and crosspoint memory CM 41 The subsequent crosspoint memories also store data according to the input from the previous resistive crossbar network. 11 ,···,CM m1 ) are provided on the same first wiring S1, and the cross point memories (CM11, . . . , CM m1 ), that is, a signal of the weighted sum of the data stored in each cross point memory (CM 11 ,···,CM m1 ) is output to the electronic neuron NR1 and stored. m Similarly, in the crosspoint memory (CM1 n ,···,CM mn ) and the data is stored in the crosspoint memory (CM 1n ,···,CM mn ) is the signal of the weighted sum of the data stored in the electronic neuron NR n The output is stored in the electronic neurons (N1,...,NR n ) is configured to be input to the next stage of the resistive crossbar network.

[0065] 17 is a circuit diagram of an example of an AI system using a magnetoresistive effect element. n The reference element REF is connected in series with the electronic neuron NR n The reference element REF is a magnetoresistive element similar to the transistor TR.SIG via the power supply voltage V DD is input, and the electronic neuron NR n is connected to the ground. A read enable signal SIG is input and the transistor TR SIG When turned on, the reference element REF is supplied with the power supply voltage V DD is entered.

[0066] In the above configuration, the electronic neuron NR n When the data "1" is stored and the resistance is high, the electronic neuron NR n The output from the connection point of the reference element REF becomes high potential, and the high potential signal passes through two inverters in series and is applied to the transistor TR +VS and transistor TR -VS The +VS and -VS signals are input to the next stage resistor crossbar network NW n+1 is entered into

[0067] In the above configuration, when the electronic neuron NRn stores data "0" and has a low resistance, the electronic neuron NR n The output from the connection point of the reference element REF becomes low potential, and the low potential signal passes through two inverters connected in series and is input to the transistor TR +VS and transistor TR -VS As a result, the +VS signal and the -VS signal are input to the next stage resistive crossbar network NW n+1 is not entered.

[0068] In this way, an AI system is constructed using magnetoresistive effect elements according to an embodiment of the present invention, with the output of a previous stage resistive crossbar network being input to a next stage resistive crossbar network.

[0069] Figure 18 is a diagram showing an outline of an AI system different from that shown in Figure 17. Electronic neurons (NR1,...,NR n ) has the same configuration as the magnetoresistive effect element according to the embodiment of the present invention, and further, a cross point memory (CM 11 ,···,CMmn ) also requires crosspoint memory (CM 11 ,···,CM mn The first wiring on which the first wiring is provided is connected to the common substrate (SA1, . . . , SA n ) and is composed of a laminate of a substrate 1, a buffer layer 2, and a heavy metal layer 11. In this way, using the magnetoresistive effect element according to the embodiment of the present invention, the output of the previous stage resistive crossbar network is configured to be input to the next stage resistive crossbar network, thereby forming an AI system.

[0070] FIG. 19 is a plan view of an AI system according to a sixth embodiment of the present invention. In an array of magnetoresistive effect elements constituting the AI ​​system, magnetic field application electrodes (CL1, CL2, . . .) may be provided that can select a predetermined row and apply a predetermined magnetic field to it for writing. As shown in FIG. 19, the magnetic field application electrodes (CL1, CL2, . . .) form wiring in a semicircular arc shape in a plan view on one side (the left side). A write current I is applied to the heavy metal wiring at a position where the magnetoresistive effect element to be written is located. w When current flows through the magnetoresistive element, the thermal stability constant is small, so the magnetoresistive element enters a state where "1" and "0" are not defined. In this state, for example, by passing current in a specified direction through the magnetic field application electrodes (CL1, CL2, etc.), a magnetic field in a specified direction is generated according to the flow of current, thereby performing writing.

[0071] Fig. 20 is a plan view of an AI system according to a sixth embodiment of the present invention, which is different from Fig. 19. In Fig. 20, the semicircular arc-shaped wiring portions of the magnetic field application electrode CL1 and the semicircular arc-shaped wiring portions of the magnetic field application electrode CL2 are alternately arranged on both sides of the direction in which the wiring extends. By passing a current in a predetermined direction through the magnetic field application electrodes CL1 and CL2, a magnetic field in a predetermined direction is generated in accordance with the flow of the current, thereby performing writing.

[0072] 19 and 20, the common substrate (SA1, . . . SA n ) and crosspoint memory (CM 11 ,CM 21 ,···,CM1n ,CM 2n ) other components such as second wiring are not shown so as to clarify the arrangement of the magnetic field applying electrodes (CL1, CL2A...).

[0073] [Verification experiment] Next, we will explain the results of verification experiments on magnetic multilayer films used in magnetoresistive effect elements according to any embodiment of the present invention. The following samples were fabricated. Figures 21A to 21H are cross-sectional views of the fabricated samples. Sample 100 was composed of a Si substrate 101 provided with a thermal oxide film, a 0.5-nm-thick Ta layer 102 provided on the thermal oxide film, a 1.5-nm-thick CoFeB layer 103 provided on Ta layer 102, a heavy metal layer 104 formed by alternately stacking Pt and Ir layers, and a 1.0-nm-thick Ta layer 105 on top of heavy metal layer 104.

[0074] In the first sample, as shown in FIG. 21A, the heavy metal layer 104 was made of a stack of a 0.4 nm thick Pt layer and a 0.4 nm thick Ir layer, and 2 to 10 Pt / Ir layers were fabricated so that the total thickness of the heavy metal layer 104 was 1.6 nm to 8.0 nm.

[0075] In the second sample, as shown in FIG. 21B, the heavy metal layer 104 was made of a stack of a 0.6 nm thick Pt layer and a 0.6 nm thick Ir layer, and 1 to 7 Pt / Ir layers were fabricated so that the total thickness of the heavy metal layer 104 was 1.2 nm to 8.4 nm.

[0076] In the third sample, as shown in FIG. 21C, the heavy metal layer 104 was made of a stack of a 0.8 nm thick Pt layer and a 0.8 nm thick Ir layer, and one to six Pt / Ir layers were fabricated so that the total thickness of the heavy metal layer 104 was 1.6 nm to 9.6 nm.

[0077] In the fourth sample, as shown in FIG. 21D, the heavy metal layer 104 was made of a laminate of a 1.0 nm thick Pt layer and a 0.8 nm thick Ir layer, and one to five Pt / Ir layers were fabricated so that the total thickness of the heavy metal layer 104 was 1.8 nm to 9.0 nm.

[0078] In the fifth sample, as shown in FIG. 21E, the heavy metal layer 104 was made of a laminate of a 1.2 nm thick Pt layer and a 0.8 nm thick Ir layer, and one to five Pt / Ir layers were laminated so that the total thickness of the heavy metal layer was 2.0 nm to 10.0 nm.

[0079] In the sixth sample, as shown in FIG. 21F, the heavy metal layer 104 was made of a stack of a 0.8 nm thick Pt layer and a 0.6 nm thick Ir layer, and one to five Pt / Ir layers were stacked so that the total thickness of the heavy metal layer was 1.4 nm to 7.0 nm.

[0080] In the seventh sample, as shown in FIG. 21G, the heavy metal layer 104 was made of a laminate of a 1.0 nm thick Pt layer and a 0.6 nm thick Ir layer, and one to five Pt / Ir layers were laminated so that the total thickness of the heavy metal layer was 1.6 nm to 8.0 nm.

[0081] In the eighth sample, as shown in FIG. 21H, the heavy metal layer 104 was made of a laminate of a 1.2 nm thick Pt layer and a 0.6 nm thick Ir layer, and one to five Pt / Ir layers were laminated so that the total thickness of the heavy metal layer was 1.8 nm to 9.0 nm.

[0082] As comparative samples, as shown in FIG. 21I, heavy metal layers 104 each consisting of a Pt layer alone and having thicknesses ranging from 1.5 nm to 7.0 nm were fabricated.

[0083] For each sample, the resistivity, spin Hall angle (spin generation efficiency), and spin conductivity were measured using the SMR method. xx (Ω -1) was obtained, and the dependence on the thickness t (nm) of the heavy metal layer was calculated. Figure 22 shows the dependence of the electrical conductivity of the third sample on the thickness of the heavy metal layer. The third sample was Ta 0.5 nm / CoFeB 1.5 nm / (Pt 0.8 nm / Ir 0.8 nm) n / Ta(-0) 1nm stack, where n is 1 to 5. The resistivity ρ of the heavy metal layer PtIr The resistivity of CoFeB was 44.56 μΩcm. CoFeB was 260.5 μΩcm.

[0084] 23 is a diagram showing the dependence of electrical conductivity on the thickness of the heavy metal layer of the fourth sample. The fourth sample is Ta 0.5 nm / CoFeB 1.5 nm / (Pt 1.0 nm / Ir 0.8 nm) n / Ta(-0) 1nm stack, where n is 1 to 5. The resistivity ρ of the heavy metal layer PtIr The resistivity of CoFeB was 37.21 μΩcm. CoFeB was 260.5 μΩcm.

[0085] 24 is a diagram showing the dependence of electrical conductivity on the thickness of the heavy metal layer of the fifth sample. The fifth sample is Ta 0.5 nm / CoFeB 1.5 nm / (Pt 1.2 nm / Ir 0.8 nm) n / Ta(-0) 1nm stack, where n is 1 to 5. The resistivity ρ of the heavy metal layer PtIr The specific resistance of CoFeB was 36.9992 μΩcm. CoFeB was 260.5 μΩcm.

[0086] 22 to 24, it is clear that the electrical conductivity is linear with respect to the thickness t of the heavy metal layer 104. In addition, as the ratio of the thickness of the Pt layer to the thickness of the Ir layer constituting the laminated film (t_Pt / t_Ir) increases, the resistivity ρ PtIr was found to be smaller.

[0087] FIG. 25 shows the resistivity results for the first to fifth samples, calculated from the thickness dependence of the electrical conductivity of the heavy metal layer 104. Results for a comparative sample and the ninth sample, which will be described later, are also shown. From FIG. 25, it was found that the resistivity ρ was lower for a laminated film of Pt and Ir layers than for Pt alone, and that a laminated film of Pt and Ir layers is more preferable as a heavy metal layer than a Pt layer alone. In particular, it was found that the resistivity decreased significantly when the thickness ratio of the Pt layer to the Ir layer was greater than 1.

[0088] For the first to fifth samples, the spin generation efficiency θ of the magnetic laminated film SH , spin conductivity σ SH The results are shown in Figures 26 and 27. Figures 26 and 27 also show the results for the comparative sample and the ninth sample. The horizontal axis of Figure 26 shows the thickness ratio of the Pt layer to the Ir layer in each sample in its stacked state, and the vertical axis shows the spin generation efficiency θ SH The spin generation efficiency θ SH When the thickness of the Pt layer and the Ir layer is 0.4 / 0.4 or 0.6 / 0.6, it is lower than that of a single Pt layer, but when the thickness of the Pt layer and the Ir layer is 0.8 / 0.8, 1.0 / 0.8, or 1.2 / 0.8, it has the same level as that of a single Pt layer.

[0089] The horizontal axis of FIG. 27 shows the thickness ratio of the Pt layer to the Ir layer in each sample, and the vertical axis shows the spin conductivity σ SH The spin conductivity σ SH It was found that when the thickness of the Pt layer and the Ir layer was 0.4 / 0.4 and 0.6 / 0.6, it was lower than that of a single Pt layer, but when the thickness of the Pt layer and the Ir layer was 0.8 / 0.8, 1.0 / 0.8, and 1.2 / 0.8, it was higher than that of a single Pt layer.

[0090] Similarly, for the sixth, seventh, and eighth samples, the spin generation efficiency θ SH , specific resistance ρ xx , spin conductivity σ SHThe results are shown in Figures 28 to 30. Figures 28 to 30 also show the third to fifth samples. The horizontal axis of each figure is the thickness ratio of the Pt layer to the Ir layer in each sample, and the vertical axis is the spin generation efficiency θ SH , and in Figure 29, resistivity ρ XX , and in Figure 30, the spin conductivity σ SH The case where the Ir layer is 0.8 nm thick is shown by the black circle (●) plot, and the case where the Ir layer is 0.6 nm thick is shown by the diamond (◇) plot.

[0091] From Figure 28, the spin generation efficiency θ SH In both cases where the Ir layer thickness is 0.6 nm and 0.8 nm, the spin generation efficiency θ increases as the Pt layer thickness increases to 0.8 nm, 1.0 nm, and 1.2 nm. Compared to the case where only Pt is used (approximately 0.1), when the Ir layer thickness t_Ir is 0.6 nm and 0.8 nm, the Pt layer thickness t_Pt is in the range of 0.8, 1.0, and 1.2 nm, and a sufficient spin generation efficiency θ SH When the thickness of the Ir layer t_Ir is 0.6 nm and the thickness of the Pt layer t_Pt is 0.6 nm, the spin generation efficiency θ SH is about 0.07, which is not very desirable.

[0092] From Figure 29, the resistivity ρ xx When the Ir layer thickness was 0.6 nm or 0.8 nm, the resistivity ρ decreased as the Pt layer thickness increased to 0.8 nm, 1.0 nm, and 1.2 nm. Compared to the case of a Pt layer alone (65 μΩcm), when the Ir layer thickness t_Ir was 0.6 nm or 0.8 nm, the Pt layer thickness t_Pt was in the range of 0.8, 1.0, and 1.2 nm. xx When the thickness of the Ir layer t_Ir is 0.6 nm and the thickness of the Pt layer t_Pt is 0.6, the resistivity ρ xx is about 50μΩcm, which is not very desirable.

[0093] From Figure 30, the spin conductivity σ SHIn both cases where the Ir layer thickness is 0.6 nm and 0.8 nm, the coefficient of electrical conductivity increases as the Pt layer thickness increases to 0.8 nm, 1.0 nm, and 1.2 nm. 5 Ω -1 m -1 ), high spin conductivity σ is observed when the Ir layer thickness t_Ir is 0.6nm and 0.8nm and the Pt layer thickness t_Pt is in the range of 0.8, 1.0, and 1.2nm. SH When the thickness of the Ir layer t_Ir is 0.6 nm and the thickness of the Pt layer t_Pt is 0.6, the spin conductivity σ SH is about 1.4 x 10 5 Ω -1 m -1 So I don't really like it.

[0094] The above verification experiments revealed the following: 1) As a heavy metal layer, a repeated stack of Ir and Pt layers is preferable to a single Pt layer, as this reduces the resistivity. Pt has low resistance, but grains grow easily, making it highly resistive in a thin film state. The stacked structure allows for the reduction of resistivity without reducing inversion efficiency. 2) The Ir layers constituting the heavy metal layer should preferably have a thickness of 0.6 nm or more per layer. 3) The Pt layers constituting the heavy metal layer preferably have a thickness of more than 0.6 nm per layer. If the thickness of each layer is small, for example, if the thickness of each Pt layer / Ir layer is 0.4 nm, the spin conductivity σ SH This is because the efficiency is worse than that of Pt alone (see Figure 27). 4) The thickness ratio of the Pt layer to the Ir layer in the heavy metal layer is preferably in the range of 1:0.5 to 1:0.8. 5) The heavy metal layer as a whole preferably has a thickness of 10 nm or less. The thickness of the heavy metal layer is sufficient if it is about 3 to 4 times the spin diffusion length, and it can be thin as long as it can pass a current. This is because making it thicker than necessary does not affect the recording layer. 6) Each of the Pt layer and Ir layer constituting the heavy metal layer includes one layer, and may be, for example, Pt layer / Ir layer / Pt layer or Ir layer / Pt layer / Ir layer.

[0095] 21J is a cross-sectional view of the fabricated ninth sample. The ninth sample 100 includes a Si substrate 111 with a thermal oxide film, a 0.5-nm-thick Ta layer 112 provided on the thermal oxide film, a 1.5-nm-thick CoFeB layer 113 provided on the Ta layer 112, a 1.2-nm-thick MgO layer 114 provided on the CoFeB layer 113, a heavy metal layer 115 formed by alternately stacking a 1.0-nm-thick Pt layer and a 0.8-nm-thick Ir layer, a 1.5-nm-thick CoFeB layer 116 provided on the heavy metal layer 115, a 1.5-nm-thick MgO layer 117 provided on the CoFeB layer 116, and a 1.0-nm-thick Ta layer 118 provided on the MgO layer 117. The heavy metal layer 115 was made by stacking a 1.0 nm thick Pt layer and a 0.8 nm thick Ir layer, and stacks of 1 to 6 Pt / Ir layers were fabricated so that the total thickness of the heavy metal layer was 1.6 nm to 9.6 nm.

[0096] 31 is a diagram showing the dependence of electrical conductivity on the thickness of the heavy metal layer of the ninth sample. The ninth sample is Ta 0.5 nm / CoFeB 1.5 nm / MgO 1.2 nm / (Pt 1.0 nm / Ir 0.8 nm) n / CoFeB1.5nm / MgO1.5nm / Ta(-0)1nm. Resistivity of the heavy metal layer ρ PtIr The resistivity of CoFeB was 34.016 μΩcm. CoFeB was 260.5 μΩcm.

[0097] For the ninth sample, the spin generation efficiency θ SH , spin conductivity σ SH In the ninth sample, the pinhole generation efficiency θ SH is approximately 0.1, and the resistivity ρ PtIr is 35μΩcm, and the spin conductivity σ SH is 3.2 × 10 5 Ω -1 m -1This was found to be a more preferable value for a magnetic laminated film (heavy metal layer) compared to the fourth sample.

[0098] Comparing the value of resistivity ρ obtained for the ninth sample with the results of other samples in Figure 25, it was found that by providing magnetic layers CoFeB above and below the laminated structure of a Pt layer and an Ir layer, the resistivity was reduced to 35 μΩcm, which was preferable.

[0099] Spin Hall angle θ obtained for the 9th sample SH The value of the spin Hall angle θ is compared with the results of the first to fifth samples from FIG. 26. By providing magnetic layers CoFeB above and below the laminated structure of the Pt layer and the Ir layer, SH It was found that the spin Hall angle increased to 0.108, which is favorable. Note that the spin Hall angle of the Ir monolayer is very small, reported to be 0.01 (PHYSICAL REVIEW B99,134421,2019).

[0100] Spin conductivity σ obtained for the ninth sample SH Comparing the values ​​of the first to fifth samples from FIG. 27, it can be seen that the spin conductivity σ SH is 3.2 × 10 5 Ω -1 m -1 It was found that the increase was favorable.

[0101] From Figures 25 to 27, the pinhole generation efficiency θ SH , specific resistance ρ PtIr , spin conductivity σ SH Therefore, it was found that it is preferable to provide magnetic layers CoFeB above and below the stack of Pt and Ir layers. Also, it is thought that providing an MgO layer makes the Pt or Ir layer adjacent to the MgO layer crystalline.

[0102] 32 is a diagram showing the dependence of electrical conductivity on the thickness of the heavy metal layer. The horizontal axis represents the thickness of the heavy metal layer, and the vertical axis represents electrical conductivity Gxx (Ω -1) The square (■), diamond (◆), and circle (●) plots indicate that the sample is CoFeB / MgO / (Pt1.0 / Ir0.8), respectively. n , (Pt1.0 / Ir0.8) n , Pt. Pt, (Pt1.0 / Ir0.8) n , MgO / (Pt1.0 / Ir0.8) n It was found that the resistivities of the respective materials decreased in the order of 64.8 μΩcm, 37.2 μΩcm, and 34.0 μΩcm.

[0103] As described above, when magnetic layers are provided above and below the heavy metal layer, the spin Hall generation rate θ SH , spin conductivity σ SH It was also revealed that the characteristics of the magnetoresistance effect element are improved. Based on this finding, the magnetoresistance effect elements according to the second and third embodiments described with reference to Figs. 9 and 11 are envisioned. The following description will be made with particular reference to Fig. 9. The heavy metal layer 11 is configured by providing one ferromagnetic layer 14 and the other ferromagnetic layer 15 of Co above and below a Pt layer 13 / Ir layer 12. It is generally known that in Co / Ir / Co, strong antiferromagnetic coupling occurs between Co and Co via Ir. However, Ir has a low spin generation efficiency θ SH As shown above, the inventors have found that the Pt layer 13 / Ir layer 12 has a large spin generation efficiency θ SH , spin conductivity σ SH It was found that the following can be obtained.

[0104] Therefore, we fabricated a tenth sample by forming a Co layer on a Pt / Ta underlayer, then forming an Ir layer and a Pt layer on the Co layer, and then forming a Co layer on the Pt layer, with the Pt layer as a cap layer. We investigated the magnetic coupling between the Ir / Pt spacers in multiple samples, with the Pt layer thickness ranging from 0.6 nm to 1.0 nm.

[0105] Figure 33 shows the results of investigating the interlayer magnetic coupling between the Ir / Pt spacers of the 10th sample. The horizontal axis represents the thickness of the Ir layer, t Ir and the vertical axis is the interlayer bonding force J exFrom Figure 33, we confirmed that strong antiferromagnetic coupling was achieved even through the Ir / Pt spacer. The spin generation efficiency θ SH , spin conductivity σ SH Regarding the characteristics of (Pt1.0 / Ir0.8) in Figures 26 and 27 n , (Pt1.2 / Ir0.8) n (where n is 1 to 5, inclusive, including the case where n is 1). Furthermore, when this Co / Ir / Pt / Co electrode is used, ferromagnetic Co layers are provided above and below the Ir / Pt. Therefore, as shown in Figure 10, when the direction of the write current is changed, antiferromagnetic coupling occurs between the upper and lower Co layers, and the magnetization direction in the Co layer is simultaneously reversed without generating any leakage magnetic field. This in turn reverses the magnetization of the memory layer of the MTJ, and it was found that a good SOT device can be fabricated.

[0106] Here, the thickness of the Ir layer is preferably 0.45 to 0.65 nm, or 1.3 to 1.5 nm, which provides antiferromagnetic (AF) bonding, as shown in Figure 33. The thickness of the Pt layer is preferably 0.6 to 1.0 nm. The thickness of Co is preferably 1 nm or less.

[0107] We investigated whether the interface between the heavy metal layer and the recording layer should be a Pt layer or an Ir layer. Table 1 shows the spin generation efficiency θ when the interface between the heavy metal layer and the recording layer is a Pt layer or an Ir layer. SH , resistivity ρ (μΩcm), spin conductivity σ SH 1 is a table showing the results. From Table 1, it is clear that the interface between the heavy metal layer and the recording layer is preferably formed by a Pt layer rather than an Ir layer. From this, it can be said that in each of the above-mentioned embodiments, the interface between the heavy metal layer 11 and the recording layer side is preferably formed by a Pt layer.

[0108] [Table 1]

[0109] We estimated the extent to which power consumption could be reduced by the heavy metal layer structure. Table 2 summarizes the relative power consumption values ​​for each heavy metal layer structure. Table 2 shows that power consumption decreases relatively significantly as the thickness ratio of the Pt layer to the Ir layer becomes 0.4nm / 0.4nm, 0.6nm / 0.6nm, 0.8nm / 0.8nm, 1.0nm / 0.8nm, and 1.2nm / 0.8nm. Furthermore, we found that by providing magnetic layers of CoFeB on both sides and sandwiching an MgO layer, power consumption decreases relatively from 0.33 to 0.26.

[0110] [Table 2]

[0111] Fig. 34 is a schematic diagram of a Hall bar and measurement system fabricated as an eleventh sample. Fig. 35A is a cross-sectional view of the fabricated eleventh sample. As shown in Fig. 35A, the eleventh sample was composed of a Si substrate 201 provided with a thermal oxide film, a 3-nm-thick Ta layer 202 provided on the thermal oxide film, a heavy metal layer 203 provided on the Ta layer 202, which was composed of four alternating layers of 1.0-nm-thick Pt layers and 0.8-nm-thick Ir layers, a 1.3-nm-thick Co layer 204 provided on the heavy metal layer 203, a 0.6-nm-thick Ir layer 205 provided on the Co layer 204, a 0.6-nm-thick Pt layer 206 provided on the Ir layer 205, and a 3-nm-thick Ta layer 207 provided on the Pt layer 206.

[0112] 35B is a cross-sectional view of another comparative sample. As shown in FIG. 35B, the comparative sample was composed of Si substrate 201 having a thermal oxide film formed thereon, 3-nm-thick Ta layer 202 formed on the thermal oxide film, 7.2-nm-thick Pt layer 203a formed on Ta layer 202, 1.3-nm-thick Co layer 204 formed on Pt layer 203a, 0.6-nm-thick Ir layer 205 formed on Co layer 204, 0.6-nm-thick Pt layer 206 formed on Ir layer 205, and 3-nm-thick Ta layer 207 formed on Pt layer 206.

[0113] The 11th sample and another comparative sample were processed into Hall bars as shown in Figure 34 using photolithography and Ar ion milling. A pulse current I was applied in the y direction, and the Hall voltage V was measured. The Hall resistance R xy The pulse current I dependence of R (Ω) was measured. xy (Ω)=V / I.

[0114] Figure 36 shows the Hall resistance R of the first sample and another comparative sample. xy The horizontal axis shows the pulse current I (mA) and the vertical axis shows the Hall resistance R xy During the measurement, a pulse current I was applied for 200 μs, and a constant external magnetic field H ex This is the result when -26mT is applied in the direction of the pulse current I (φ=0 degrees). When a pulse current is applied in the positive direction, the Hall resistance R xy When the current is applied in the negative direction, the Hall resistance R xy Since a decrease in the magnetic moment was observed, it was found that the magnetization of the Co layer 204 was reversed by the pulse current.

[0115] When the absolute values ​​of the reversal current of Sample 11 and another comparative sample were examined, it was found that the reversal current when the heavy metal layer 203 used a multilayer film electrode of Pt and Ir layers was approximately 70% smaller than the reversal current when an electrode of Pt layer 203a was used.

[0116] Resistivity ρ of Pt with a thickness of 7.2 nm xx and the resistivity ρ of a four-layer stack of Pt1.0nm and Ir0.8nm (Pt1.0nm / Ir0.8nm) xx The values ​​of xx = 37.2 μΩcm, the reduction in the spin switching current is due to the Pt / Ir multilayer film having a higher spin conversion efficiency θ SH This is thought to be due to an increase in

[0117] The thickness of the Pt layer and Ir layer constituting the heavy metal layer may be constant or may vary for each Pt layer and Ir layer. Each MTJ may have either perpendicular magnetization or in-plane magnetization.

[0118] The magnetoresistive element according to the embodiment of the present invention is fabricated by depositing each element in order using sputtering or the like, and then performing a heat treatment while applying a magnetic field in the direction in which the magnetization direction is desired. [Explanation of symbols]

[0119] 1: Circuit board 2: Buffer layer 10, 30, 50: Magnetoresistive element 11: Heavy metal layer 12: Ir layer 13: Pt layer 14: One ferromagnetic layer 15: The other ferromagnetic layer 16: Recording layer 17: Barrier layer 18: Reference layer 19: Cap layer 60: Magnetic memory

Claims

1. a heavy metal layer formed by laminating an Ir layer and a Pt layer; a recording layer including a first ferromagnetic layer having reversible magnetization, the first ferromagnetic layer being disposed opposite the heavy metal layer; a reference layer comprising a second ferromagnetic layer having a fixed direction of magnetization; a barrier layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer and made of an insulator; Equipped with the Pt layer, which is the outermost layer of the heavy metal layer, forms an interface with the recording layer; the Ir layer of the heavy metal layer has a thickness of 0.6 nm or more and 1.5 nm or less per layer, A magnetoresistive element in which the direction of magnetization in the first ferromagnetic layer is reversed by a write current flowing through the heavy metal layer.

2. The magnetoresistive effect element of claim 1, wherein the thickness ratio of the Pt layer to the Ir layer in the heavy metal layer is in the range of 1:0.5 to 1:0.

8.

3. A heavy metal layer formed by laminating an Ir layer and a Pt layer; a recording layer including a first ferromagnetic layer having reversible magnetization, the first ferromagnetic layer being disposed opposite the heavy metal layer; a reference layer comprising a second ferromagnetic layer having a fixed direction of magnetization; a barrier layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer and made of an insulator; Equipped with a thickness ratio of the Pt layer to the Ir layer in the heavy metal layer is in the range of 1:0.5 to 1:0.8; A magnetoresistive element in which the direction of magnetization in the first ferromagnetic layer is reversed by a write current flowing through the heavy metal layer.

4. A magnetoresistive effect element as described in claim 3, wherein the outermost Pt layer in the heavy metal layer forms an interface with the recording layer.

5. A magnetoresistive effect element as described in claim 3 or 4, wherein the Ir layer of the heavy metal layer has a thickness of 0.6 nm or more and 1.5 nm or less per layer.

6. A magnetoresistive effect element described in any one of claims 1 to 5, wherein the Pt layer of the heavy metal layer has a thickness of 0.6 nm or more and 1.5 nm or less per layer.

7. A magnetoresistive effect element described in any one of claims 1 to 6, wherein the heavy metal layer is formed by repeatedly stacking the Ir layer and the Pt layer.

8. A heavy metal layer formed by laminating an Ir layer and a Pt layer; a recording layer including a first ferromagnetic layer having reversible magnetization, the first ferromagnetic layer being disposed opposite the heavy metal layer; a reference layer comprising a second ferromagnetic layer having a fixed direction of magnetization; a barrier layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer and made of an insulator; Equipped with the heavy metal layer is formed by laminating one Ir layer and one Pt layer, and providing separate ferromagnetic layers on the recording layer side and the opposite side of the recording layer, respectively; A magnetoresistive element in which the direction of magnetization in the first ferromagnetic layer is reversed by a write current flowing through the heavy metal layer.

9. A heavy metal layer formed by laminating an Ir layer and a Pt layer; a recording layer including a first ferromagnetic layer having reversible magnetization, the first ferromagnetic layer being disposed opposite the heavy metal layer; a reference layer comprising a second ferromagnetic layer having a fixed direction of magnetization; a barrier layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer and made of an insulator; Equipped with the Pt layer, which is the outermost layer of the heavy metal layer, forms an interface with the recording layer; the Pt layer of the heavy metal layer has a thickness of 0.6 nm or more and 1.5 nm or less per layer, A magnetoresistive element in which the direction of magnetization in the first ferromagnetic layer is reversed by a write current flowing through the heavy metal layer.

10. The magnetoresistive effect element of claim 9, wherein the heavy metal layer is formed by repeatedly stacking the Ir layer and the Pt layer.

11. A magnetoresistive effect element described in any one of claims 1 to 10, wherein the shapes of the recording layer, the barrier layer and the reference layer when viewed in the stacking direction of the heavy metal layer are asymmetric with respect to any line in the direction along the write current in the heavy metal layer.

12. A magnetoresistive effect element described in any one of claims 1 to 10, wherein the shapes of the recording layer, the barrier layer and the reference layer when viewed in the stacking direction of the heavy metal layer are symmetrical with respect to any line in the direction along the write current in the heavy metal layer.

13. A magnetic memory comprising a plurality of magnetoresistive effect elements according to any one of claims 1 to 12, each of which includes the recording layer, the barrier layer, and the reference layer, provided on the same heavy metal layer.

14. An artificial intelligence system in which the magnetoresistive effect element described in any one of claims 1 to 12 is used in an electronic neuron to which a weighted sum of a resistive crossbar network is input.

15. An artificial intelligence system as described in claim 14, wherein the magnetoresistive effect element is used in a crosspoint memory of a resistive crossbar network.

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