Magnetic sensor

Abstract

To provide a magnetic sensor that can improve heat resistance and reduce power consumption for magnetization reversal of a ferromagnetic material.SOLUTION: A magnetic sensor according to an embodiment includes a detection layer 901 including YPtBi, a non-magnetic half-Heusler alloy topological semimetal having a Dirac-type surface state and a spin Hall angle greater than 1, and a ferromagnet 902 in contact with the detection layer and having a magnetization oriented in the in-plane direction of a first surface in contact with the detection layer.SELECTED DRAWING: Figure 22

Description

[Technical Field]

[0001] Embodiments of the present invention relate to a spin injection source, magnetic memory, spin Hall oscillator, computer, and magnetic sensor using topological materials. [Background technology]

[0002] Ferromagnetic materials exhibit a magnetoresistance effect, where their resistance changes depending on the direction of magnetization. For this reason, ferromagnetic materials are attracting attention for applications in magnetic memory, which utilizes the direction of magnetization to record information. Furthermore, domain-wall driven magnetic memory, which utilizes domain wall movement in ferromagnetic materials, is gaining attention as a high-capacity memory application exceeding NAND flash memory. Moreover, the magnetization of ferromagnetic materials can undergo precession at speeds of several GHz or higher. Therefore, ferromagnetic materials are expected to have applications in spin Hall oscillators and in computers, including neuromorphic computers, that utilize these spin Hall oscillators.

[0003] One of the fundamental technologies for these devices is the control of the magnetization direction of ferromagnetic materials. The mainstream method for controlling magnetization uses spin current, which is the flow of electron spin angular momentum. Spin current generation methods can be broadly classified into two types.

[0004] The first method involves passing an electric current through a ferromagnetic material and generating a spin-polarized current through the spin filtering effect of the ferromagnetic material. With this method, the direction of magnetization of a ferromagnetic material can be controlled by passing this spin-polarized current through the ferromagnetic material to be controlled. This method is called the Spin Transfer Torque (STT) method. As an example of the application of the STT method, Figure 1 shows an example of the cell structure of an STT magnetic memory (STT-MRAM: Magnetoresistive Random Access Memory). An STT magnetic memory has a structure in which a non-magnetic insulator, which functions as a tunnel barrier layer, is provided between a ferromagnetic material having the magnetization to be controlled (magnetization free layer) and a ferromagnetic material for generating spin current (magnetization fixed layer). By passing an electric current perpendicular to the surface of the ferromagnetic material, a spin current is generated parallel to the current. At this time, the efficiency of spin current generation is determined by the spin polarizability P of the ferromagnetic material used in the magnetization fixed layer. However, the spin polarization P is generally small, between 0.5 and 0.8, and in principle cannot exceed 1. Therefore, STT magnetic memory requires a large current for magnetization control. This high-current magnetization control has been one of the causes of device degradation. The requirement of a large current for magnetization control is an inherent problem of the STT method and is common to all devices utilizing the STT method.

[0005] To solve this problem, a second approach utilizing the spin Hall effect (SHE) is attracting attention. SHE is a phenomenon in which a spin current is generated perpendicular to the current when an electric current is injected into a non-magnetic material. Heavy metals and topological insulators with strong spin-orbit interaction are known as materials with strong SHE. These materials can be candidates for spin injection source materials. The method utilizing SHE is called the spin orbit torque (SOT) method. As an example of the application of the SOT method, an example of the cell structure of a SOT magnetic memory (SOT-MRAM) is shown in Figure 2. The SOT method has a stacked structure similar to the STT method, but also has a spin injection source (spin Hall layer) in contact with the magnetized free layer. In the SOT method, the direction of the current and the spin current are orthogonal. Therefore, the effective spin current generation efficiency is determined by the spin Hall angle, which represents the strength of SHE, and the length L of the magnetized free layer. FM and the thickness of the spin hole layer t SH Ratio L FM / t SH This is based on the product of the two factors. Thus, the SOT method can improve spin current generation efficiency not only through spin Hall materials but also through structural improvements. Furthermore, the spin Hall angle and ratio L FM / t SH Since both can exceed 1, it is easy to reduce the amount of current required for magnetization control.

[0006] From the viewpoint of spin current generation efficiency, it is desirable for the spin Hall layer material to have a large spin Hall angle. On the other hand, since the spin Hall layer is in contact with the magnetized free layer, a portion of the current injected into the spin Hall layer is diverted to the magnetized free layer. Therefore, it is desirable for the spin Hall material to have an electrical conductivity equal to or greater than that of the ferromagnetic material of the magnetized free layer. Due to the magnitude of the magnetoresistance effect, ferromagnetic materials such as CoFe alloys are used for the magnetized free layer material, so the spin Hall material should have a conductivity of 10 5 It is desirable to have an electrical conductivity of S / m or higher.

[0007] 10 5As spin hall materials having a high electrical conductivity exceeding S / m, heavy metals such as Pt, Ta, and W have been studied. However, as shown in Non-Patent Documents 1 to 3, since the spin hall angle of heavy metals is as small as around 0.1, the effect of reducing the magnetization control current amount is limited. On the other hand, as materials having a giant spin hall angle of 1 or more, topological insulators such as Bi2Se3 or Bi2Te3 are known. The spin hall angles of these materials are characterized by being caused by strong anti-damping torque generated from the Dirac-type surface state. As shown in Non-Patent Documents 4 to 6, these materials have a low electrical conductivity of 10 3 ~10 4 S / m. However, a spin hall angle of more than 1 is promising from the viewpoint of the generation efficiency of spin current. In recent years, a BiSb alloy, which is a kind of topological insulator capable of achieving both a high electrical conductivity exceeding 10 5 S / m and a giant spin hall angle of more than 1, has been developed. As shown in Patent Document 1, by using a BiSb alloy as a spin hall material, it is possible to reduce the magnetization control current amount by more than one digit compared to the STT method.

[0008] Topological insulators have a spin hall angle of more than 1 due to the Dirac-type surface state. Therefore, it is possible to achieve a higher spin current generation efficiency than heavy metals. However, since existing topological insulators are mainly composed of Group V and Group VI elements, they have a low melting point and have a problem of low affinity with semiconductor manufacturing processes involving heating at 400 °C or higher.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Non-Patent Documents

[0010]

Non-Patent Document 1

[0011] One embodiment of the present invention provides a spin injection source having high heat resistance exceeding 400°C and capable of reducing power consumption, as well as a magnetic memory, spin Hall oscillator, computer, and magnetic sensor utilizing the same. [Means for solving the problem]

[0012] The magnetic sensor according to this embodiment includes a detection layer containing YPtBi, which is a non-magnetic half-Heusler alloy topological semimetal having a Dirac-type surface state and a spin Hall angle greater than 1, and a ferromagnetic material in contact with the detection layer and having magnetization oriented in the in-plane direction of the first surface in contact with the detection layer. In a ferromagnetic material, by passing an electric current perpendicular to the first plane and injecting a spin-polarized current into YPtBi, a voltage dependent on the magnetization direction of the ferromagnetic material is generated by the inverse spin Hall effect of YPtBi. [Brief explanation of the drawing]

[0013] [Figure 1] This figure shows an example of the cell structure of an STT-type magnetic memory. [Figure 2]This figure shows an example of the cell structure of a SOT-type magnetic memory. [Figure 3] This figure shows the film deposition temperature dependence of the X-ray diffraction spectrum of YPtBi in the first embodiment. [Figure 4] This figure shows the results of composition ratio analysis of YPtBi by X-ray fluorescence analysis in the first embodiment. [Figure 5] This figure shows the structure of Sample 1 used for evaluating the spin Hall angle in the first embodiment. [Figure 6] This figure shows the structure of sample 2 used for spin Hall angle evaluation in the first embodiment. [Figure 7] This figure shows an overview of the measurement circuit used for evaluating the spin Hall angle in the first embodiment, and the coordinate system for measurement. [Figure 8] This figure shows the dependence of the second harmonic component of the Hall resistance in Sample 1 on the external magnetic field in the first embodiment. [Figure 9] In the first embodiment, this figure shows the relationship between the anti-damping magnetic field and the current density in the YPtBi layer in Sample 1. [Figure 10] This table shows the spin Hall angles measured using CoTb and the spin Hall angles corrected for the spin dissipation effect of CoTb for various spin Hall materials, including YPtBi. [Figure 11] This figure shows the relationship between Hall resistance and the in-plane application angle of the magnetic field in the first embodiment. [Figure 12] This table shows the absolute value of the spin Hall angle, electrical conductivity, and normalized power consumption for each spin Hall material. [Figure 13] This table shows the heat resistance, toxic substances, SHE, electrical conductivity, and surface roughness of topological insulators and HHA-TSM. [Figure 14] This figure shows an example of the cell structure of a 3-terminal SOT magnetic memory according to the first example of the first embodiment. [Figure 15] This shows an example of the cell structure of a two-terminal SOT magnetic memory according to a second example of the first embodiment. [Figure 16] This figure shows an example of a cell structure of a magnetic memory according to the second embodiment. [Figure 17] This figure shows an example of a three-terminal spin Hall oscillator according to the first example of the third embodiment. [Figure 18] This figure shows an example of a two-terminal spin Hall oscillator according to the second example of the third embodiment. [Figure 19] This figure shows an example of a two-terminal spin Hall oscillator according to the third example of the third embodiment. [Figure 20] This figure shows an example of a two-terminal spin Hall oscillator according to the fourth example of the third embodiment. [Figure 21] This figure shows an example of an artificial neuron using a spin Hall oscillator according to the fourth embodiment. [Figure 22] This figure shows an example of a magnetic sensor according to the fifth embodiment. [Modes for carrying out the invention]

[0014] Embodiments will be described below with reference to the drawings. In the following description, components having the same function and configuration will be denoted by the same reference numerals.

[0015] 1. First Embodiment Below, as a first embodiment, we will describe a spin injection source and magnetic memory using YPtBi, one of the Half Heusler Alloy - Topological Semi-Metals (HHA-TSM), as the spin Hall material.

[0016] 1.1 Characteristics of YPtBi First, the properties of YPtBi will be described as an example of HHA-TSM. Note that the material of HHA-TSM is not limited to this. For example, it may be one of the ternary alloys having a half-Heusler structure, consisting of two transition metals or rare earth elements and one metal belonging to a main group element, or a mixed crystal thereof. More specifically, for example, HHA-TSM may be LuPtSb, LuPdBi, LuPtBi, ScPtBi, YAuPb, LaPtBi, CePtBi, ThPtPb, and LaAuPb, or mixed crystals thereof.

[0017] 1.1.1 Heat resistance First, the heat resistance of YPtBi will be explained with reference to Figures 3 and 4. Figure 3 shows the film deposition temperature dependence of the X-ray diffraction spectrum of YPtBi. Figure 4 shows the composition ratio analysis results of YPtBi by X-ray fluorescence analysis.

[0018] Figures 3 and 4 show the results of evaluating the crystal structure and composition ratio of YPtBi, respectively, using samples in which YPtBi was deposited on a substrate at a thickness of approximately 50 nm while varying the substrate temperature using the simultaneous sputtering method. The substrate temperature range was 300 to 800°C. c-Sapphire was used as the substrate. In addition, a YPt target and a Bi target were used for the simultaneous sputtering method.

[0019] First, let's explain the crystal structure of YPtBi by referring to Figure 3.

[0020] As shown in Figure 3, focusing on the peaks in the (111) plane of YPtBi, peaks originating from the (111) plane of YPtBi were observed in the substrate temperature range of 300 to 600°C.

[0021] Next, the composition ratio of YPtBi will be explained with reference to Figure 4. In Figure 4, the vertical axis represents the composition ratio of Bi to Y (yttrium). The horizontal axis represents the substrate temperature during YPtBi film deposition.

[0022] As shown in Figure 4, at substrate temperatures below 600°C, the Bi composition ratio is stable at 1, which is the ideal crystal structure for the half-Heusler alloy. This result is consistent with the temperature range in which the peak attributable to the (111) plane of YPtBi was obtained in the X-ray diffraction spectrum shown in Figure 3.

[0023] These results indicate that YPtBi can maintain its half-Heusler structure even when heated above 400°C. Therefore, HHA-TSM can have heat resistance above 400°C. Furthermore, since YPtBi can be deposited over a wide temperature range by sputtering, HHA-TSM can have high compatibility with mass production processes for semiconductor devices.

[0024] 1.1.2 Electrical conductivity Next, the electrical conductivity of YPtBi will be described. The electrical conductivity was measured using the four-terminal method with samples in which approximately 11 nm of YPtBi was deposited on a c-sapphire substrate and an SiO2 / Si substrate. The substrate temperature when the YPtBi was deposited by simultaneous sputtering was 600°C. As a result of the four-terminal method measurement, the electrical conductivity of YPtBi on the c-sapphire substrate was, for example, 1.17 × 10⁻⁶. 5 The conductivity was S / m. Furthermore, the electrical conductivity of YPtBi on an SiO2 / Si substrate was, for example, 1.57 × 10⁻⁶. 5 It was S / m. Therefore, YPtBi is 10 5 It has high electrical conductivity exceeding S / m.

[0025] 1.1.3 Spin Hole Angle Next, we will explain the spin Hall angle of YPtBi.

[0026] 1.1.3.1 Sample Structure and Evaluation Method The sample structure and measurement circuit for spin Hall angle measurement will be described with reference to Figures 5 to 7. In this embodiment, two types of samples were used. Figure 5 is a cross-sectional view of sample 1. Figure 6 is a cross-sectional view of sample 2. Figure 7 is a diagram showing the overview of the measurement circuit and the measurement coordinate system.

[0027] First, we will describe the structures of Sample 1 and Sample 2, which were used to measure the spin Hall angle. Sample 1 and Sample 2 each have a heterojunction between YPtBi and a ferromagnetic material.

[0028] As shown in Figure 5, Sample 1 includes a c-sapphire substrate, YPtBi, Pt, Co, and MgAl2O4. For example, a YPtBi layer with a thickness of approximately 10 nm is formed on the c-sapphire substrate. On the YPtBi, for example, layers of Pt with a thickness of approximately 0.5 nm, Co with a thickness of approximately 0.5 nm, and Pt with a thickness of approximately 0.5 nm are alternately stacked. The Pt / Co / Pt stack functions as a ferromagnetic CoPt. CoPt has perpendicular magnetic anisotropy. For example, a layer of MgAl2O4 with a thickness of approximately 2 nm is formed on the top layer of Pt. The MgAl2O4 functions as a capping layer to prevent oxidation.

[0029] As shown in Figure 6, Sample 2 includes a Si substrate, SiO2, YPtBi, CoTb, and MgAl2O4. SiO2 is formed on the Si substrate. The thickness of the SiO2 layer is arbitrary. YPtBi, for example, with a thickness of approximately 10 nm, is formed on the SiO2. CoTb, for example, with a thickness of approximately 3 nm, is formed on the YPtBi. CoTb is ferromagnetic. CoTb exhibits in-plane magnetic anisotropy. MgAl2O4, for example, with a thickness of approximately 2 nm, is formed on the CoTb.

[0030] The applications of Sample 1 and Sample 2 are described below. Generally, a heterojunction of a spin Hall layer and a ferromagnetic material is used for measuring the spin Hall angle. In this case, spin dissipation occurs at the interface between the two layers. The magnitude of spin dissipation strongly depends on the type of ferromagnetic material. CoPt used in Sample 1 is a material with relatively small spin dissipation. Therefore, when using Sample 1, it is possible to evaluate the spin Hall angle without correcting for spin dissipation. The advantage of the structure of Sample 1 is that the uncertainty factor of spin dissipation correction is small. On the other hand, when comparing spin Hall angles between multiple spin Hall materials, it is desirable to use the same ferromagnetic material. For this reason, CoTb, which has a relatively large track record of being used for evaluating the spin Hall angle of various spin Hall materials, was used as the ferromagnetic material for Sample 2.

[0031] Next, we will explain the evaluation method for the spin Hall angle. The second harmonic method was used to evaluate the spin Hall angle. The second harmonic method involves the second harmonic Hall resistance R generated when an alternating current is applied to a sample. H 2ω This method evaluates the spin Hall angle from the dependence of the external magnetic field. For example, in the measurement circuit shown in Figure 7, an alternating current is passed between terminal -I and terminal +I. Then, terminal +V H and terminal -V H The second harmonic component of the Hall voltage due to the anomalous Hall effect occurring between the two is measured. At this time, the external magnetic field H ext It is applied parallel to the current.

[0032] The evaluation procedure involves first calculating the spin Hall angle by fitting the second harmonic Hall resistance R based on Equation 1. H 2ω From anti-damping-like magnetic field H DL Extract it.

[0033]

number

[0034] Here, R AHEThis is abnormal Hall resistance, H K eff This is the effective plane-orthogonal anisotropic magnetic field, R PHE H is a planar hole resistor. FL+OF C is the sum of the field-like magnetic field and the Oersted magnetic field. out ONE This is the normal Nernst effect caused by the perpendicular temperature gradient, R out ANE+SSE These are the anomalous Nernst effect and spin Seebeck effect caused by the perpendicular temperature gradient. In Equation 1, H is used when there is perpendicular magnetic anisotropy. K eff >0, H if in-plane magnetic anisotropy is present. K eff <0. Also, in equation 1, H DL H FL+OF H K eff , C out ONE , R out ANE+SSE These are the fitting parameters.

[0035] Next, H extracted using Equation 2 DL Convert this to the spin Hall angle.

[0036]

number

[0037] Here, e is the elementary charge, M S t is the saturation magnetization. FM is the thickness of the ferromagnetic material, h is Planck's constant, and J NM This is the current density of the YPtBi layer. As a result, the spin Hall angle θ SH This is calculated.

[0038] 1.1.3.2 Specific Examples of Measurement Results of External Magnetic Field Dependence and Spin Hall Angle Next, referring to Figures 8 and 9, the second harmonic Hall resistor R H 2ω The dependence of the external magnetic field and the spin Hall angle θ SHSpecific examples of the measurement results are described below. Figure 8 shows the dependence of the second harmonic component of the Hall resistance in Sample 1 on the external magnetic field. Each plot in Figure 8 shows the measured value, and the solid line shows the fitting result according to Equation 1. The amplitude of the applied AC current is between 1.0 and 3.4 mA. The example in Figure 8 shows the case where the AC current is changed in increments of 0.4 mA. The frequency of the AC current is 259.68 Hz. Figure 9 shows the relationship between the anti-damping magnetic field and the current density in YPtBi in Sample 1.

[0039] As shown in Figure 9, anti-damping-like magnetic field H DL This is the current density J of YPtBi. NM It is increasing in proportion to H. DL / J NM The ratio of and the saturation magnetization M obtained, for example, by a superconducting quantum interferometer. S = 632 emu / cm 3 Substitute this into Equation 2, and the spin Hall angle θ SH When calculated, the value is approximately 1.3. Therefore, the spin Hall angle θ for which YPtBi exceeds 1. SH It has been demonstrated that it possesses [this characteristic].

[0040] Similarly, for sample 2 using CoTb, the spin Hall angle was measured using the second harmonic method. As a result, for example, H DL / J NM = 5.98Oe·cm 2 / MA, saturation magnetization M S = 456 emu / cm 3 The spin Hall angle θ of YPtBi is obtained. SH A value of 0.25 was obtained. In general, using CoTb, the spin Hall angle θ SH When measured, the spin Hall angle θ is higher than when measured with other ferromagnetic materials due to the spin dissipation effect of CoTb. SH It is known that this is underestimated by about 1 / 5 to 1 / 10. A similar trend was observed with YPtBi.

[0041] 1.1.3.3 Comparison of spin Hall angles with other spin Hall materials Next, referring to Figure 10, the spin Hall angle θ of YPtBi SH This section describes the results of comparing this material with other spin Hall materials. Figure 10 shows the spin Hall angles (θ) measured using CoTb for various spin Hall materials, including YPtBi. SH (CoTb) and the spin Hall angle (Intrinsic θ) corrected for the spin dissipation effect of CoTb SH This is a table showing the following. Note that in the example in Figure 10, the θ of YPtBi SH (CoTb) shows the measurement results for sample 2, and Intrinsic θ SH The results shown are for the measurement of Sample 1. The spin Hall materials used for comparison with YPtBi include the heavy metals Ta and Pt, as well as the topological insulators Bi2Se3, (Bi,Sb)2Te3, and BiSb.

[0042] As shown in Figure 10, the spin Hall angle θ SH Focusing on (CoTb), the spin Hall angle θ of YPtBi SH (CoTb) is 0.25. The spin Hall angle θ of YPtBi SH (CoTb) is defined by the spin Hall angle θ of the heavy metals Ta and Pt. SH Compared to (CoTb), it is about an order of magnitude larger. Also, the spin Hall angle θ of YPtBi is SH When (CoTb) is compared with the topological insulators Bi2Se3, (Bi,Sb)2Te3, and BiSb, its properties are about an order of magnitude lower than BiSb, but comparable to those of Bi2Se3 and (Bi,Sb)2Te3.

[0043] Next, the spin Hall angle (Intrinsic θ) SH Focusing on this, the spin Hall angle (Intrinsic θ) of YPtBi SH ) is 1.3. Therefore, the spin Hall angle θ of YPtBi is 1.3. SH (CoTb) is the spin Hall angle (Intrinsic θ) SH It is about one-fifth of the spin Hall angle θ of heavy metals and topological insulators. SH(CoTb) has a spin Hall angle (intrinsic θ SH ) that is about one-fifth to one-tenth of that of YPtBi. Therefore, the measurement results of YPtBi show a similar trend to those of other spin Hall materials.

[0044] 1.1.4 Magnetic field dependence of Hall resistance Next, referring to Fig. 11, to confirm that YPtBi has a Dirac-type surface state, the magnetic field dependence of the Hall resistance R H will be explained based on the measurement results using a sample with YPtBi deposited on a substrate. Fig. 11 is a graph showing the relationship between the Hall resistance R H and the in-plane application angle φ H of the magnetic field. Note that c-Sapphire was used for the substrate of the Hall resistance R H measurement sample. The substrate temperature during YPtBi film deposition was 600 °C. The vertical axis of the graph in Fig. 11 is the Hall resistance R H obtained when an in-plane rotating magnetic field was applied to the aforementioned sample. The horizontal axis is the in-plane application angle φ H of the magnetic field. Here, the in-plane application angle φ H of the magnetic field is based on the direction parallel to the applied direct current. The measurement temperature was 4 K, and the magnitude of the magnetic field was 7.6 kOe. The black dot plots in the graph indicate the measured values, and the solid line indicates the fitting curve.

[0045] As shown in Fig. 11, the measured values of the Hall resistance R H can be well explained by a fitting curve (solid line) that includes the first-order symmetric components of cosφ H and sinφ H , and the second-order symmetric component of sin2φ H . The Hall resistance R HThe one-fold symmetric component originates from the normal Hall effect caused by the deviation of the magnetic field application angle from the in-plane direction. On the other hand, the two-fold symmetric component is a magnetoresistance effect called the planar Hall effect, which is caused by the Dirac-type topological surface state in the non-magnetic YPtBi. That is, the presence of the planar Hall effect indicates that the non-magnetic YPtBi has a Dirac-type surface state. Therefore, it can be said that the giant spin Hall angle in YPtBi is due to the strong anti-damping torque arising from the Dirac-type surface state.

[0046] 1.1.5 Power Consumption When Reversing the Magnetization of a Magnetic Material Next, referring to Fig. 12, the power consumption when reversing the magnetization of a magnetic material provided on a spin Hall material will be described. Fig. 12 is a table showing the absolute value of the spin Hall angle θ SH of each spin Hall material, the electrical conductivity, and the normalized power consumption. The example in Fig. 12 shows the case when a heavy metal or HHA-TSM is used as the type of spin Hall material. More specifically, the example in Fig. 12 shows the case when Ta, Pt, or W with a film thickness of 6 nm is used as the heavy metal and the case when YPtBi with a film thickness of 10 nm is used as the HHA-TSM. The normalized power consumption indicates the value obtained by normalizing the power consumption when reversing the magnetization of CoFeB (magnetic material) with a film thickness of 1.5 nm with the power consumption when Ta is used as 1.

[0047] As shown in Fig. 12, the absolute value of the spin Hall angle θ SH of YPtBi as HHA-TSM is larger than that of the heavy metals Ta, Pt, and W. Ta, Pt, W, and YPtBi all have a high electrical conductivity of 1.0×10 5 S / m or more. The normalized power consumptions of Pt and W with respect to Ta are 3.6×10 -1 and 1.6×10 -1 respectively. In contrast, the normalized power consumption of YPtBi with respect to Ta is 3.3×10 -2Therefore, when YPtBi is used as the spin Hall material, the power consumption is 3.3% of that when Ta is used. Furthermore, the power consumption when using YPtBi is about one-fifth of that when using W, which has the lowest power consumption among heavy metals.

[0048] Thus, the inventors of this application have found that HHA-TSM containing YPtBi can reverse the magnetization of magnetic materials with lower power consumption than heavy metals.

[0049] 1.1.6 Comparison with Topological Insulators Next, we will discuss the results of comparing topological insulators and HHA-TSM with reference to Figure 13. Figure 13 is a table showing the heat resistance, toxic substances, SHE, electrical conductivity, and surface roughness of topological insulators and HHA-TSM. Here, toxic substances indicate whether or not toxic materials are included as components of the material.

[0050] As shown in Figure 13, the heat resistance of topological insulators is approximately 300°C or less, while that of HHA-TSM is approximately 600°C. In the back-end processes of semiconductor manufacturing, materials are required to have a heat resistance of 400°C or higher, so HHA-TSM has a higher compatibility with semiconductor manufacturing processes than topological insulators.

[0051] For example, materials such as Sb, Se, or Te that can be included in topological insulators are toxic. In contrast, HHA-TSM can be composed of non-toxic materials such as YPtBi.

[0052] The SHE of both topological insulators and HHA-TSM is strong compared to heavy metals, meaning they have a large spin Hall angle. Furthermore, the electrical conductivity of topological insulators, with the exception of BiSb, tends to be relatively low. In contrast, the electrical conductivity of HHA-TSM is relatively high.

[0053] HHA-TSM has a lower surface roughness than topological insulators. Therefore, it also reduces the surface roughness of the interface between the HHA-TSM and the magnetic material. This improves the perpendicular magnetic anisotropy of the magnetic material.

[0054] Thus, the inventors of this application have found that HHA-TSM containing YPtBi has high heat resistance exceeding 400°C, is a material that does not contain toxic substances, and has relatively low surface roughness. In other words, the inventors of this application have found that HHA-TSM has a higher affinity for semiconductor device manufacturing processes than topological insulators as a spin Hall material.

[0055] 1.2 Configuration of Magnetic Memory Next, we will describe two examples of magnetic memory configurations using an HHA-TSM as a spin injection source. In the following descriptions, one of the source and drain of a transistor will be referred to as "one end of the transistor," and the other of the source and drain of a transistor will be referred to as "the other end of the transistor."

[0056] 1.2.1 Example 1 First, let's explain the first example. In the first example, we will explain an example of the cell structure of a 3-terminal SOT magnetic memory, referring to Figure 14. Figure 14 is a diagram showing an example of the cell structure of a 3-terminal SOT magnetic memory.

[0057] As shown in Figure 14, the SOT magnetic memory 100 comprises a magnetic memory element 101, a spin injection source 102, a write transistor 103, and a read transistor 104. The magnetic memory element 101 is a memory element (hereinafter also referred to as "MTJ element") that has a magnetoresistive effect due to a magnetic tunnel junction (MTJ).

[0058] The MTJ element 101 includes a ferromagnetic material 111, an insulator 112, and a ferromagnetic material 113. For example, the ferromagnetic material 113, the insulator 112, and the ferromagnetic material 111 are stacked in order on the spin injection source 102.

[0059] The ferromagnetic material 111 is ferromagnetic and has an easy magnetization axis perpendicular to the film surface. The magnetization direction of the ferromagnetic material 111 is fixed. That is, the ferromagnetic material 111 functions as a magnetization fixed layer. The magnetization direction of the ferromagnetic material 111 does not change due to the spin current injected from the spin injection source 102.

[0060] The insulator 112 is in contact with the ferromagnetic materials 111 and 113 and is provided between the ferromagnetic materials 111 and 113. The insulator 112 is a non-magnetic insulator. The insulator 112 functions as a tunnel barrier layer. MgO is preferably used for the insulator 112. However, other materials such as AlO may be used for the insulator 112. In addition, a metal oxide containing at least one of Ga, Al, Mg, Hf, and Zr may be used for the insulator 112.

[0061] The ferromagnetic material 113 is ferromagnetic and has an easy magnetization axis perpendicular to the film surface. The magnetization direction of the ferromagnetic material 113 is controlled by a spin current injected from the spin injection source 102. In other words, the ferromagnetic material 113 functions as a magnetization free layer.

[0062] When the magnetization direction of ferromagnetic material 111 and the magnetization direction of ferromagnetic material 113 are parallel, the MTJ element 101 is in a low resistance state. On the other hand, when the magnetization direction of ferromagnetic material 111 and the magnetization direction of ferromagnetic material 113 are antiparallel, the MTJ element 101 is in a high / low resistance state. Data is assigned according to the resistance state of the MTJ element 101.

[0063] Ferromagnetic materials 111 and 113 each contain at least one of the following elements: Co, Fe, Ni, Mn, B, Si, Zr, Nb, Ta, Ru, Ir, Pt, Ga, Al, Pd, Tb, and Gd. Ferromagnetic materials 111 and 113 may also be laminates consisting of multiple layers. Furthermore, ferromagnetic materials 111 and 113 may have the same configuration or different configurations.

[0064] The spin injection source 102 includes an HHA-TSM. For example, YPtBi is used as the HHA-TSM. A writing transistor 103 is connected to one end of the HHA-TSM in a direction parallel to the film surface of the HHA-TSM. The other end of the HHA-TSM facing the other end is grounded (connected to a ground voltage wire).

[0065] One end of the writing transistor 103 is connected to the spin injection source 102 (HHA-TSM), and the other end is connected to a power supply (not shown), for example. A control signal is input to the gate of the writing transistor 103.

[0066] One end of the readout transistor 104 is connected to the ferromagnetic material 111 of the MTJ element 101, and the other end is connected to a readout circuit (not shown), for example. A control signal is input to the gate of the readout transistor 104.

[0067] For example, when writing data to the MTJ element 101 in memory 100, the writing transistor 103 is turned ON and the reading transistor 104 is turned OFF. Then, current flows from the power supply to ground via the ON writing transistor 103 and the spin injection source 102. At this time, a pulsed current (hereinafter referred to as "in-plane current") flows in a direction parallel to the plane at the surface of the HHA-TSM (spin injection source 102) that is in contact with the ferromagnetic material 113. When a pulsed in-plane current flows through the HHA-TSM, a spin current is generated in a direction perpendicular to the plane. Then, the spin current is injected from the HHA-TSM into the ferromagnetic material 113 (magnetization free layer). The resultant force of the anti-damping torque generated by the spin current and the torque generated by the external magnetic field (in-plane bias magnetic field) applied parallel to the in-plane current causes a magnetization reversal of the ferromagnetic material 113, that is, the magnetization direction is controlled, and data is written to the MTJ element 101.

[0068] For example, when reading data from the MTJ element 101, the write transistor 103 is turned off, and the read transistor 104 is turned on. A read current flows from the power supply to the MTJ element 101 through the on-state read transistor 104. At this time, the data from the MTJ element 101 is read based on the resistance value of the MTJ element 101.

[0069] 1.2.2 Example 2 Next, we will describe a second example. In this second example, we will describe an example of the cell structure of a two-terminal SOT magnetic memory, referring to Figure 15. Figure 15 is a diagram showing an example of the cell structure of a two-terminal SOT magnetic memory.

[0070] As shown in Figure 15, the SOT magnetic memory 200 includes an MTJ element 201, a spin injection source 202, and a write / read transistor 203. The difference from the first example is that the transistor connected to the MTJ element 201 is eliminated, and the ferromagnetic material 211 is grounded.

[0071] The configuration of the MTJ element 201 is the same as that of the MTJ element 101 in the first example. More specifically, the MTJ element 201 includes a ferromagnetic material 211, an insulator 212, and a ferromagnetic material 213. The ferromagnetic material 211 functions as a magnetization fixed layer, similar to the ferromagnetic material 111. The insulator 212 functions as a tunnel barrier layer, similar to the insulator 112. The ferromagnetic material 213 functions as a magnetization free layer, similar to the ferromagnetic material 113.

[0072] The spin injection source 202 includes an HHA-TSM. For example, YPtBi is used as the HHA-TSM.

[0073] One end of the write / read transistor 203 is connected to one end of the HHA-TSM (spin injection source 202), and the other end is connected to a power supply (not shown), for example. A control signal is input to the gate of the write / read transistor 203.

[0074] For example, when writing data to the MTJ element 201, the write / read transistor 203 is turned ON. Then, current flows from the power supply to ground through the write / read transistor 203, spin injection source 202, ferromagnet 213, insulator 212, and ferromagnet 211. At this time, a pulsed in-plane current flows through the HHA-TSM (spin injection source 202), injecting a spin current from the spin injection source 202 into the ferromagnet 213 (magnetized free layer). The anti-damping torque generated by the spin current causes magnetization reversal of the ferromagnet 213, and data is written. At this time, the spin polarization current generated from the ferromagnet 211 can also assist in the magnetization reversal of the ferromagnet 213. By assisting in the magnetization reversal of the spin polarization current generated from the ferromagnetic material 211, magnetization reversal can be performed without an external magnetic field (in-plane bias magnetic field), regardless of the orientation relationship between the easy magnetization axis of the ferromagnetic material 213 and the spin quantization axis of the spin current generated from the spin injection source 202.

[0075] 1.3 Effects according to this embodiment The inventors of this application have found that HHA-TSM exhibits a large spin Hall angle greater than 1 due to a Dirac-type surface state, and 10 5 The inventors of this invention have found that HHA-TSM possesses high electrical conductivity exceeding S / m and consumes less power when reversing the magnetization of magnetic materials than heavy metals. Furthermore, they have found that HHA-TSM has high heat resistance exceeding 400°C. In other words, the inventors have found that HHA-TSM has excellent properties as a spin Hall material and good compatibility with semiconductor manufacturing processes. By using HHA-TSM as a spin injection source, the power consumption for reversing the magnetization of ferromagnetic materials can be reduced. In addition, by applying HHA-TSM as a spin injection source for SOT magnetic memory, the write current and write power of the SOT magnetic memory can be reduced.

[0076] 2. Second Embodiment Next, a second embodiment will be described. In the second embodiment, a magnetic wall-driven type magnetic memory different from that of the first embodiment will be described. The following description will focus on the differences from the first embodiment.

[0077] 2.1 Configuration of Magnetic Memory The configuration of magnetic memory will be explained with reference to Figure 16. Figure 16 shows an example of the cell structure of magnetic memory.

[0078] As shown in Figure 16, the magnetic memory 300 includes a ferromagnetic material 301, a spin injection source 302, a reading unit 303, conductors 304-306, a ferromagnetic material 307, and terminals T1-T4. In the following description, the direction parallel to the film surface of the ferromagnetic material 301 and moving from conductor 304 toward conductor 306 is denoted as the X direction. The direction parallel to the film surface of the ferromagnetic material 301 and intersecting the X direction is denoted as the Y direction. The direction perpendicular to the film surface of the ferromagnetic material 301 is denoted as the Z direction.

[0079] The ferromagnetic material 301 is provided on top of the spin injection source 302. The ferromagnetic material 301 is ferromagnetic and has an easy magnetization axis in the Z direction perpendicular to the film surface. The ferromagnetic material 301 functions as a magnetization free layer. The ferromagnetic material 301 contains a plurality of magnetic domains MD separated by domain walls DW. One magnetic domain MD functions as one memory element. In the example in Figure 16, the ferromagnetic material 301 contains four magnetic domains MD1 to MD4. The magnetic domains MD1 to MD4 are arranged in a row in the X direction. The ferromagnetic material 301 contains at least one of Co, Fe, Ni, Mn, B, Si, Zr, Nb, Ta, Ru, Ir, Pt, Ga, Al, Pd, Tb, and Gd. The ferromagnetic material 301 may be a laminate consisting of multiple layers.

[0080] The spin injection source 302 includes an HHA-TSM. For example, YPtBi is used as the HHA-TSM.

[0081] The reading unit 303 reads the magnetization direction of the magnetic domain MD (magnetic domain MD1 in the example of Figure 16). The reading unit 303 includes a ferromagnetic material 311 and an insulator 312.

[0082] The ferromagnetic material 311 is ferromagnetic and has an easy magnetization axis in the Z direction perpendicular to the film surface. The magnetization direction of the ferromagnetic material 311 is fixed. That is, the ferromagnetic material 311 functions as a magnetization-fixed layer. The magnetization direction of the ferromagnetic material 311 does not change due to the spin current injected from the spin injection source 302. The ferromagnetic material 311 contains at least one of Co, Fe, Ni, Mn, B, Si, Zr, Nb, Ta, Ru, Ir, Pt, Ga, Al, Pd, Tb, and Gd. The ferromagnetic material 311 may be a laminate consisting of multiple layers.

[0083] The insulator 312 is in contact with one magnetic domain of the ferromagnetic material 301 (magnetic domain MD1 in the example of Figure 16) and the ferromagnetic material 311, and is provided between the ferromagnetic material 301 and the ferromagnetic material 311. The insulator 312 is a non-magnetic insulator. The insulator 312 functions as a tunnel barrier layer. MgO is preferably used for the insulator 112. However, other materials such as AlO may be used for the insulator 312. In addition, a metal oxide containing at least one of Ga, Al, Mg, Hf, and Zr may be used for the insulator 312.

[0084] The MTJ element is composed of a ferromagnetic material 311, an insulator 312, and one magnetic domain MD of the ferromagnetic material 301 in contact with the insulator 312. In other words, the readout unit 303 includes the MTJ element.

[0085] Conductors 304 to 306 are provided on the ferromagnetic material 301 along the X direction. Conductors 304 to 306 may be provided on the spin injection source 302, or they may be in contact with both the ferromagnetic material 301 and the spin injection source 302. Conductor 304 is provided near the end of the ferromagnetic material 301 in the X direction. Conductor 305 is provided in the X direction at a position away from conductor 304, with the readout section 303 in between. One magnetic domain MD is formed in the ferromagnetic material 301 in a region including the contact surface with conductors 304 and 305. Conductor 306 is provided in the X direction near the end of the ferromagnetic material 301 opposite to the end of conductor 304 that is in contact with conductor 304. Conductors 304 to 306 contain conductive material. Conductor 305 may be omitted.

[0086] The ferromagnetic material 307 is positioned in the Z direction, spaced apart from the spin injection source 302 via an insulator (not shown). Above the ferromagnetic material 307 in the Z direction, conductors 304 and 305 are positioned via the spin injection source 302 and the ferromagnetic material 301. The ferromagnetic material 307 is ferromagnetic and has an easy magnetization axis in the X direction parallel to the film surface. The magnetization direction of the ferromagnetic material 307 is fixed. The ferromagnetic material 307 provides a bias magnetic field to the ferromagnetic material 301 and the spin injection source 302. The bias magnetic field is used to reverse the magnetization direction of the ferromagnetic material 301 during writing. The ferromagnetic material 307 contains at least one of Co, Fe, Ni, Mn, B, Si, Zr, Nb, Ta, Ru, Ir, Pt, Ga, Al, Pd, Tb, and Gd. The ferromagnetic material 307 may be a laminate consisting of multiple layers.

[0087] Terminal T1 is connected to conductor 304. Terminal T2 is connected to conductor 305. Terminal T3 is connected to readout unit 303 (ferromagnetic material 311). Terminal T4 is connected to conductor 306.

[0088] For example, when writing data to magnetic domain MD1, a writing current flows between terminals T1 and T2. The writing current flows through the ferromagnetic material 301 (magnetization free layer) and the HHA-TSM (spin injection source 302). A pulsed in-plane current flows through the HHA-TSM, injecting a spin current into the ferromagnetic material 301. The anti-damping torque generated by the spin current causes a magnetization reversal of magnetic domain MD1 in the ferromagnetic material 301, and the data is written.

[0089] For example, when reading data from magnetic domain MD1, a read current flows between terminal T3 and terminal T1 or terminal T2. Based on the resistance value of the MTJ element of the readout unit 303, the magnetization direction (data) of magnetic domain MD1 is read out.

[0090] For example, when moving a magnetic domain MD, a current for driving the magnetic domain wall flows between terminals T1 and T4. When current flows through the HHA-TSM and the ferromagnetic material 301, the magnetic domain walls DW of the ferromagnetic material 301, i.e., the magnetic domain MDs, move. This movement of magnetic domain walls makes it possible to control the magnetization direction of each magnetic domain MD within the ferromagnetic material 301. By a similar principle, the reading unit 303 can read the magnetization direction of each magnetic domain MD within the ferromagnetic material 301.

[0091] 2.2 Effects according to this embodiment With the configuration according to this embodiment, the HHA-TSM can be applied to a magnetic memory with a magnetic domain wall drive.

[0092] 3. Third Embodiment Next, a third embodiment will be described. In the third embodiment, four examples will be described in which the HHA-TSM is applied to the spin injection source of a spin Hall oscillator. The following description will focus on the differences from the first and second embodiments.

[0093] 3.1 Example 1 First, let's describe the first example. In this first example, we will describe a three-terminal spin Hall oscillator with reference to Figure 17. Figure 17 is a diagram showing an example of a three-terminal spin Hall oscillator.

[0094] As shown in Figure 17, the three-terminal spin Hall oscillator 400 includes an MTJ element 401, a spin injection source 402, a magnetization drive transistor 403, and a power supply terminal 404 for the MTJ.

[0095] The MTJ element 401 includes a ferromagnetic material 411, an insulator 412, and a ferromagnetic material 413. For example, the ferromagnetic material 413, the insulator 412, and the ferromagnetic material 411 are stacked in order on top of the spin injection source 402.

[0096] The ferromagnetic material 411 is ferromagnetic and has a hard magnetization axis similar to that of the ferromagnetic material 413. The magnetization direction of the ferromagnetic material 411 is fixed. That is, the ferromagnetic material 411 functions as a fixed magnetization layer. The magnetization direction of the ferromagnetic material 411 does not change due to the spin current injected from the spin injection source 402.

[0097] The insulator 412 is in contact with the ferromagnetic materials 411 and 413 and is provided between the ferromagnetic materials 411 and 413. The insulator 412 is a non-magnetic insulator. The insulator 412 functions as a tunnel barrier layer. MgO is preferably used for the insulator 412. However, other materials such as AlO may be used for the insulator 412. In addition, a metal oxide containing at least one of Ga, Al, Mg, Hf, and Zr may be used for the insulator 412.

[0098] The ferromagnetic material 413 possesses ferromagnetism and has a hard magnetization axis or easy magnetization axis parallel to the spin quantization axis of the spin current injected into the ferromagnetic material 413 from the spin injection source 402. The ferromagnetic material 413 functions as a magnetization free layer. The magnetization of the ferromagnetic material 413 can precess due to the spin current injected from the spin injection source 402. Furthermore, the frequency and amplitude of the precession can be modulated by applying an external magnetic field (in-plane bias magnetic field) parallel to the hard magnetization axis or easy magnetization axis of the ferromagnetic material 413.

[0099] Ferromagnetic materials 411 and 413 contain at least one of Co, Fe, Ni, Mn, B, Si, Zr, Nb, Ta, Ru, Ir, Pt, Ga, Al, Pd, Tb, and Gd. Ferromagnetic materials 411 and 413 may be laminates consisting of multiple layers. Furthermore, ferromagnetic materials 411 and 413 may have the same configuration or different configurations.

[0100] The spin injection source 402 includes an HHA-TSM. For example, YPtBi is used as the HHA-TSM.

[0101] One end of the magnetization drive transistor 403 is connected to one end of the HHA-TSM (spin injection source 402), and the other end is connected to a power supply (not shown), for example. A control signal is input to the gate of the magnetization drive transistor 403. The other end of the HHA-TSM (spin injection source 402) opposite to the end to which the magnetization drive transistor 403 is connected is grounded.

[0102] The MTJ power supply terminal 404 is connected to the ferromagnetic material 411 of the MTJ element 401. The current supplied from the MTJ power supply terminal 404 allows for the electrical detection of the magnetization direction of the ferromagnetic material 413 due to the tunneling magnetoresistive (TMR) effect occurring in the MTJ element 401.

[0103] When the spin Hall oscillator 400 is operated as an oscillator, the magnetization driving transistor 403 is turned ON. An in-plane current flows from one end of the spin injection source 402 to the other end through the ON magnetization driving transistor 403. When an in-plane current flows through the HHA-TSM (spin injection source 402), a spin current is injected into the ferromagnetic material 413. This causes the magnetization of the ferromagnetic material 413 to precess. The precession of the magnetization of the ferromagnetic material 413 is converted into an electrical signal by the TMR effect of the MTJ element 401. This signal is then output as an AC voltage from a voltage output terminal (not shown) connected to the ferromagnetic material 411.

[0104] 3.2 Second Example Next, we will describe a second example. In this second example, we will describe a two-terminal spin Hall oscillator with reference to Figure 18. Figure 18 is a diagram showing an example of a two-terminal spin Hall oscillator.

[0105] As shown in Figure 18, the two-terminal spin Hall oscillator 500 includes a ferromagnetic material 501, a spin injection source 502, and a magnetization drive transistor 503.

[0106] The ferromagnetic material 501 is provided on top of the spin injection source 502. The ferromagnetic material 501 has ferromagnetism and a hard magnetization axis parallel to the spin quantization axis of the spin current injected into the ferromagnetic material 501 from the spin injection source 502. The ferromagnetic material 501 functions as a magnetization free layer. The magnetization of the ferromagnetic material 501 can precess due to the spin current injected from the spin injection source 502. Furthermore, by applying an external magnetic field (in-plane bias magnetic field) parallel to the hard magnetization axis of the ferromagnetic material 501, the frequency and amplitude of the precession can be modulated.

[0107] The ferromagnetic material 501 contains at least one of Co, Fe, Ni, Mn, B, Si, Zr, Nb, Ta, Ru, Ir, Pt, Ga, Al, Pd, Tb, and Gd. The ferromagnetic material 501 may also be a laminate consisting of multiple layers.

[0108] The spin injection source 502 includes an HHA-TSM. For example, YPtBi is used as the HHA-TSM.

[0109] One end of the magnetization drive transistor 503 is connected to one end of the HHA-TSM (spin injection source 502), and the other end is connected to a power supply (not shown), for example. A control signal is input to the gate of the magnetization drive transistor 503. The other end of the HHA-TSM (spin injection source 502) opposite to the end to which the magnetization drive transistor 503 is connected is grounded.

[0110] When the spin Hall oscillator 500 is operated as an oscillator, the magnetization driving transistor 503 is turned ON. An in-plane current is supplied from one end of the spin injection source 502 to the other end via the ON magnetization driving transistor 503. When an in-plane current flows through the HHA-TSM (spin injection source 502), a spin current is injected into the ferromagnetic material 501. This causes the magnetization of the ferromagnetic material 501 to precess. The precession of the magnetization of the ferromagnetic material 501 is output to the outside as a leakage magnetic field generated from the magnetization.

[0111] 3.3 Third Example Next, we will describe a third example. In this third example, we will describe a two-terminal spin Hall oscillator that differs from the second example, referring to Figure 19. Figure 19 is a diagram showing an example of a two-terminal spin Hall oscillator.

[0112] As shown in Figure 19, the two-terminal spin Hall oscillator 600 includes an MTJ element 601, a spin injection source 602, and a magnetization drive transistor 603.

[0113] The configuration of the MTJ element 601 is the same as that of the MTJ element 401 in the first example. More specifically, the MTJ element 601 includes a ferromagnetic material 611, an insulator 612, and a ferromagnetic material 613. For example, the ferromagnetic material 613, the insulator 612, and the ferromagnetic material 611 are stacked in order on the spin injection source 602. The ferromagnetic material 611 functions as a magnetization fixed layer, similar to the ferromagnetic material 411. Unlike the first example, the ferromagnetic material 611 is grounded. The insulator 612 functions as a tunnel barrier layer, similar to the insulator 412. The ferromagnetic material 613 functions as a magnetization free layer, similar to the ferromagnetic material 413.

[0114] The spin injection source 602 includes an HHA-TSM. For example, YPtBi is used as the HHA-TSM.

[0115] One end of the magnetization drive transistor 603 is connected to one end of the HHA-TSM (spin injection source 602), and the other end is connected to a power supply, for example, not shown. A control signal is input to the gate of the magnetization drive transistor 603.

[0116] When the spin Hall oscillator 600 is operated as an oscillator, the magnetization driving transistor 603 is turned ON. Current flows from the spin injection source 602 towards the ferromagnetic material 611 through the ON magnetization driving transistor 603. When an in-plane current flows through the HHA-TSM (spin injection source 602) at this time, a spin current is injected into the ferromagnetic material 613. As a result, the magnetization of the ferromagnetic material 613 precesses. Since the current input through the magnetization driving transistor 603 flows through the MTJ element 601, the direction of the magnetization of the ferromagnetic material 613 can be electrically detected by the TMR effect generated in the MTJ element 601. As a result, the precession of the magnetization of the ferromagnetic material 613 is converted into an electrical signal by the TMR effect of the MTJ element 601 and output as an AC voltage from a voltage output terminal (not shown) connected to the spin injection source 602.

[0117] 3.4 Case 4 Next, we will describe the fourth example. In the fourth example, we will describe a two-terminal spin Hall oscillator having an MTJ element and a parallel resistor, referring to Figure 20. Figure 20 is a diagram showing an example of a two-terminal spin Hall oscillator.

[0118] As shown in Figure 20, the two-terminal spin Hall oscillator 700 includes an MTJ element 701, a spin injection source 702, a resistive element 703, a conductor 704, and a magnetization drive transistor 705.

[0119] The configuration of the MTJ element 701 is the same as that of the MTJ element 401 in the first example. More specifically, the MTJ element 701 includes a ferromagnetic material 711, an insulator 712, and a ferromagnetic material 713. For example, the ferromagnetic material 713, the insulator 712, and the ferromagnetic material 711 are stacked in order on the spin injection source 702. The ferromagnetic material 711 functions as a magnetization fixed layer, similar to the ferromagnetic material 411. The insulator 712 functions as a tunnel barrier layer, similar to the insulator 412. The ferromagnetic material 713 functions as a magnetization free layer, similar to the ferromagnetic material 413.

[0120] The spin injection source 702 includes an HHA-TSM. For example, YPtBi is used as the HHA-TSM.

[0121] The resistor 703 is arranged in parallel with the MTJ element 701. One end of the resistor 703 is in contact with the spin injection source 702. For example, the resistance of the resistor 703 is lower than the resistance of the MTJ element 701.

[0122] The conductor 704 is in contact with the ferromagnetic material 711 and the other end of the resistive element 703 of the MTJ element 701. The conductor 704 is grounded. That is, the other ends of the ferromagnetic material 711 and the resistive element 703 are grounded. The conductor 704 contains a conductive material.

[0123] One end of the magnetization drive transistor 705 is connected to one end of the HHA-TSM (spin injection source 702), and the other end is connected to a power supply, for example, not shown. A control signal is input to the gate of the magnetization drive transistor 705.

[0124] When the spin Hall oscillator 700 is operated as an oscillator, the magnetization driving transistor 705 is turned ON. Current flows from the spin injection source 702 to the conductor 704 through the ON magnetization driving transistor 705. When an in-plane current flows through the HHA-TSM (spin injection source 702), a spin current is injected into the ferromagnetic material 713. This causes the magnetization of the ferromagnetic material 713 to precess. The current input through the magnetization driving transistor 705 flows from the MTJ element 701 and the resistive element 703 to the conductor 704. Since the resistance value of the resistive element 703 is lower than that of the MTJ element 701, the in-plane current of the HHA-TSM mainly flows through the resistive element 703 to the conductor 704. Therefore, the magnitude of the in-plane current can be controlled by the resistance value of the resistive element 703. In addition, a portion of the current injected through the magnetization driving transistor 705 flows through the MTJ element 701. Therefore, the TMR effect of the MTJ element 701 allows for the electrical detection of the magnetization direction of the ferromagnetic material 713. As a result, the precession of the magnetization of the ferromagnetic material 713 is converted into an electrical signal by the TMR effect of the MTJ element 701 and output as an AC voltage from a voltage output terminal (not shown) connected to the spin injection source 702.

[0125] 3.5 Effects of this embodiment With the configuration according to this embodiment, the HHA-TSM can be applied to a spin Hall oscillator.

[0126] 4. Fourth Embodiment Next, a fourth embodiment will be described. In the fourth embodiment, a spin Hall oscillator including a spin injection source including an HHA-TSM is used as the artificial neuron in the artificial neuron computer. The following description will focus on the differences from the first to third embodiments.

[0127] 4.1 Structure of Artificial Neurons Refer to Figure 21 to describe an example of the configuration of an artificial neuron. Figure 21 shows an example of an artificial neuron using a spin Hall oscillator.

[0128] As shown in Figure 21, the artificial neuron 800 includes a spin Hall oscillator 801, a DC power supply 802, an input capacitor 803, an AC power supply 804, a diode 805, an output capacitor 806, and an output terminal 807.

[0129] The spin Hall oscillator 801 includes an MTJ element 811, a spin injection source 812, and a resistive element 813.

[0130] The configuration of the MTJ element 811 is the same as that of the MTJ element 401 in the first example of the third embodiment. More specifically, the MTJ element 811 includes a ferromagnetic material 821, an insulator 822, and a ferromagnetic material 823. For example, the ferromagnetic material 823, the insulator 822, and the ferromagnetic material 821 are stacked in order on the spin injection source 812. The ferromagnetic material 821 functions as a magnetization fixed layer, similar to the ferromagnetic material 411. The ferromagnetic material 821 is grounded. The insulator 822 functions as a tunnel barrier layer, similar to the insulator 412. The ferromagnetic material 823 functions as a magnetization free layer, similar to the ferromagnetic material 413. Alternatively, the ferromagnetic material 821 may function as the magnetization free layer and the ferromagnetic material 823 may function as the magnetization fixed layer.

[0131] The spin injection source 812 includes an HHA-TSM. For example, YPtBi is used as the HHA-TSM. One end of the HHA-TSM is connected to node ND1, and the other end is connected to node ND2.

[0132] The resistor 813 is arranged in parallel with the MTJ element 811. One end of the resistor 813 is connected to node ND2. That is, one end of the resistor 813 is connected to the spin injection source 812 via node ND2. The other end of the resistor 813 is grounded. For example, the resistance value of the resistor 813 is lower than the resistance value of the MTJ element 811. Note that the resistor 813 may be omitted.

[0133] DC power supply 802 is connected to one end of HHA-TSM (spin injection source 812) via node ND1. DC power supply 802 supplies a bias DC voltage V to HHA-TSM via node ND1. DC Apply the solution.

[0134] One electrode of the input capacitor 803 is connected to node ND1, and the other electrode is connected to the AC power supply 804.

[0135] The AC power supply 804 supplies the input signal V to node ND1 via input capacitor 803. in Apply the bias DC voltage V. DC and input signal V in The combined voltage of the input signal V is applied to the HHA-TSM. For example, the input signal V in This is a voltage signal obtained by sampling time-domain input signals from audio or sensors and multiplying them by a random matrix (mask data).

[0136] One end of diode 805 is connected to node ND2, and the other end is connected to node ND3. Diode 805 is positioned to be forward biased from node ND2 to node ND3.

[0137] One electrode of output capacitor 806 is connected to node ND3, and the other electrode is grounded.

[0138] Output terminal 807 is connected to node ND3. Output voltage V is output from output terminal 807. out The following will be output.

[0139] For example, in artificial neuron 800, a bias DC voltage V is applied to the HHA-TSM. DC and input signal v in When the combined voltage is applied, an in-plane current flows through the HHA-TSM. This in-plane current injects a spin current from the HHA-TSM into the ferromagnetic material 823, causing the magnetization of the ferromagnetic material 823 to precess. This precession is output as an AC voltage via the MTJ element 811. Furthermore, the AC voltage from the MTJ element 811 is smoothed by the diode 805 and the output capacitor 806, resulting in the output voltage V of the artificial neuron 800. out The output of the spin Hall oscillator 801 is the input signal V in Because it changes nonlinearly with respect to the output voltage V of artificial neuron 800 out The input signal V in It changes nonlinearly with respect to . Therefore, the output voltage V of artificial neuron 800 out By using it as a new input signal for other artificial neurons or itself, it can be used as an artificial neuron computer.

[0140] 4.2 Effects of this embodiment With the configuration according to this embodiment, HHA-TSM can be applied to the artificial neurons of an artificial neuron computer.

[0141] Furthermore, any of the spin Hall oscillators from the first to fourth examples of the third embodiment can be applied to the spin Hall oscillator 801 used in the artificial neuron.

[0142] 5. Fifth Embodiment Next, a fifth embodiment will be described. In the fifth embodiment, a case in which HHA-TSM is used as the detection layer of the magnetic sensor will be described. The following description will focus on the differences from the first to fourth embodiments.

[0143] 5.1 Magnetic Sensor Configuration An example of a magnetic sensor configuration will be described with reference to Figure 22. Figure 22 is a diagram showing an example of a magnetic sensor.

[0144] As shown in Figure 22, the magnetic sensor 900 includes a detection layer 901, a ferromagnetic material 902, a conductor 903, current terminals 904 and 905, and voltage terminals 906 and 907. In the following description, the direction parallel to the film surface of the detection layer 901 and in which current flows through the current terminals 904 and 905 is defined as the X direction. The direction parallel to the film surface of the detection layer 901 and intersecting the X direction is defined as the Y direction. The direction perpendicular to the film surface of the detection layer 901 is defined as the Z direction.

[0145] The detection layer 901 contains an HHA-TSM. For example, YPtBi is used as the HHA-TSM.

[0146] The ferromagnetic material 902 is provided on the detection layer 901 in the Z direction. The ferromagnetic material 902 has ferromagnetism and has an easy magnetization axis direction in the direction parallel to the film surface in contact with the detection layer 901 (in-plane direction). The ferromagnetic material 902 contains at least one of Co, Fe, Ni, Mn, B, Si, Zr, Nb, Ta, Ru, Ir, Pt, Ga, Al, Pd, Tb, and Gd. The ferromagnetic material 902 may be a laminate consisting of multiple layers.

[0147] An intermediate layer may be inserted between the detection layer 901 and the ferromagnetic material 902, with the intermediate layer in contact with the detection layer 901 and the ferromagnetic material 902 at its interface. The intermediate layer may be made of a non-magnetic metal or a metal oxide containing at least one of Ga, Al, Mg, Hf, or Zr.

[0148] The conductor 903 is provided on the ferromagnetic material 902 in the Z direction. The conductor 903 includes a conductive material.

[0149] The current terminal 904 is connected to the X-direction end of the detection layer 901.

[0150] The current terminal 905 is connected to the end of the conductor 903 facing the X direction. For example, the current supplied to the current terminal 904 flows to the current terminal 905 via the conductor 903, the ferromagnetic material 902, and the detection layer 901.

[0151] The voltage terminal 906 is connected to one end of the detection layer 901 facing the Y direction.

[0152] The voltage terminal 907 is connected to the other end of the detection layer 901, which is facing in the Y direction.

[0153] A direct current is applied between the current terminals 904 and 905 of the magnetic sensor 900. As this direct current penetrates (passes through) the ferromagnetic material 902 perpendicular to the film surface (Z direction), the spin filtering effect of the ferromagnetic material 902 converts it into a spin-polarized current with a spin quantization axis parallel to the magnetization direction of the ferromagnetic material 902. As a result, a spin-polarized current is injected from the ferromagnetic material 902 into the HHA-TSM (detection layer 901) from the Z direction perpendicular to the film surface. In the HHA-TSM, the spin-polarized current is converted into current by the inverse spin Hall effect of the HHA-TSM. A portion of the converted current generates an electromotive force between the voltage terminals 906 and 907. The magnitude of the electromotive force generated between the voltage terminals 906 and 907 is proportional to the X-direction component of the magnetization of the ferromagnetic material 902. Therefore, when the X-direction component of the magnetization of the ferromagnet 902 changes due to an external magnetic field, the electromotive force generated between voltage terminals 906 and 907 in the HHA-TSM changes due to the inverse spin Hall effect. Thus, the external magnetic field can be estimated from the amount of this change.

[0154] 5.2 Effects of this embodiment With the configuration according to this embodiment, the HHA-TSM can be applied to a magnetic sensor.

[0155] 6. Others The embodiments described above have included a spin injection source, magnetic memory, spin Hall oscillator, artificial neuron computer, and magnetic sensor using HHA-TSM, but are not limited to these. HHA-TSM can also be applied to other products using spin Hall materials. For example, in a magnetic recording device, the microwaves generated by the spin Hall oscillator described in the third embodiment may be used to assist in recording.

[0156] The above embodiments can be combined as much as possible.

[0157] For example, a spin Hall oscillator may be configured by having multiple spin Hall oscillator structures identical to any of the spin Hall oscillators described in the first to fourth examples of the third embodiment, or multiple spin Hall oscillator structures from multiple examples, and by electrically or magnetically coupling them to achieve synchronization.

[0158] In the above embodiment, "connection" includes a state in which something else, such as a transistor or resistor, is interposed between the two parties for an indirect connection.

[0159] The embodiments are illustrative and the scope of the invention is not limited thereto. [Explanation of symbols]

[0160] 100, 200... SOT magnetic memory 101, 201, 401, 601, 701, 811…MTJ elements 102, 202, 302, 402, 502, 602, 702, 812… Spin injection sources 103... Writing transistor 104...Readout transistor 111, 113, 211, 213, 301, 307, 311, 411, 413, 501, 611,613, 711, 713, 821, 823, 902...Ferromagnetic material 112, 212, 312, 412, 612, 712, 822… Insulators 203…Write / Read Transistor 300… Magnetic memory 303...Reading section 304-306, 704, 903... Conductors 400, 500, 600, 700, 801... Spin Hall oscillators 403, 503, 603, 705… Transistors for magnetization drive 404…MTJ power supply terminal 703, 813… Resistor elements 800... Artificial Neuron 802…DC power supply 803...Input capacitor 804…AC power supply 805... Diode 806…Output capacitor 807…Output terminal 900…Magnetic sensor 901...Detection layer 904, 905...Current terminal 906, 907…Voltage terminals MD1~MD4…magnetic domain ND1~ND3…Nodes T1~T4... Terminals

Claims

1. A detection layer containing YPtBi, a nonmagnetic half-Heusler alloy topological semimetal having a Dirac-type surface state and a spin Hall angle greater than 1, A ferromagnetic material having magnetization that is in contact with the detection layer and whose first surface in contact with the detection layer is oriented in the in-plane direction, Equipped with, In the ferromagnetic material, by passing a current perpendicular to the first surface and injecting a spin-polarized current into YPtBi, a voltage dependent on the magnetization direction of the ferromagnetic material is generated by the inverse spin Hall effect of YPtBi. Magnetic sensor.

2. The YPtBi has heat resistance of 300°C or higher and 600°C or lower. The magnetic sensor according to claim 1.

3. A detection layer comprising YPtBi, which is a nonmagnetic half-Heusler alloy topological semimetal having a Dirac-type surface state and a spin Hall angle greater than 1, A ferromagnetic material having magnetization that is in contact with the detection layer and whose first surface in contact with the detection layer is oriented in the in-plane direction, Equipped with, The aforementioned YPtBi has heat resistance of 300°C or higher and 600°C or lower. Magnetic sensor.

4. The ferromagnetic material comprises at least one of Co, Fe, Ni, Mn, B, Si, Zr, Nb, Ta, Ru, Ir, Pt, Ga, Al, Pd, Tb, and Gd. The magnetic sensor according to any one of claims 1 to 3.

5. The YPtBi has a (111) crystal plane, The magnetic sensor according to any one of claims 1 to 4.

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