Spintronics device, magnetic memory, electronic apparatus, and method for manufacturing spintronics device

Abstract

A spintronics device 1 is provided with a generation layer 4 which is for generating a spin current and in which Al and Si are present in a mixed manner. The generation layer 4 includes a region in which variation in the composition ratios of Al and Si is within 20% of the respective average values thereof in the layer thickness direction of the generation layer 4.

Description

Spintronic device, magnetic memory, electronic device, and method for fabricating spintronic device

[0001] This disclosure relates to spintronic devices, magnetic memories, electronic devices, and methods for fabricating spintronic devices. This application claims priority to Japanese Patent Application No. 2024-153056, filed September 5, 2024, and incorporates the entire contents of said Japanese application by reference.

[0002] Patent Documents 1 and 2 disclose technologies related to spintronic devices. The spintronic device includes a first conductive layer and a second conductive layer having a carrier mobility or electrical conductivity lower than that of the first conductive layer. The boundary region between the first and second conductive layers has a gradient in carrier mobility or electrical conductivity, and a spin current is generated by the rotation of an electron velocity field caused by the gradient. Patent Document 1 describes, as an example, that the first conductive layer mainly contains copper and the second conductive layer mainly contains copper oxide. Patent Document 2 describes, as an example, a configuration in which the first conductive layer is a semiconductor layer and the second conductive layer is a metal layer.

[0003] Non-Patent Documents 1 and 2 disclose research on the diffusion motion of spins resulting from the magnetization motion of magnetic materials. Non-Patent Documents 3 and 4 disclose research on the relativistic effect of up spins and down spins scattering in opposite directions in noble metals such as platinum (Pt).

[0004] International Publication No. 2020 / 050329 International Publication No. 2023 / 106001

[0005] Mizukami et al., “The study on ferromagnetic resonance linewidth for NM / 80NiFe / NM (NM=Cu,Ta,Pd and Pt) films”, Japanese Journal of Applied Physics, 40(2A), p.580, (2001)Urban et al., “Gilbert Damping in Single and Multilayer Ultrathin Films: Role of Interfaces in Nonlocal Spin Dynamics”, Physical Review Letters, Volume 87, 217204, (2001)Kato et al., “Observation of the spin Hall effect in semiconductors”, Science, Volume 306, pp.1910-1913 (2004)Kimura et al., “Room-temperature reversible spin Hall effect”, Physical Review Letters, Volume 98, 156601 (2007)Chen et al., “Spin-torque and spin-Hall nano-oscillators”, Proceedings, IEEE, Volume 104, pp.1919-1945 (2016)An et al., “Spin-torque generator engineered by natural oxidation of Cu” Nature Communications, 7, 13069 (2016)Kontani et al. , ”Giant Orbital Hall Effect in Transition Metals: Origin of Large Spin and Anomalous Hall Effects”, Physical Review Letters 102, 016601 (2009)Go et al., "Intrinsic Spin and Orbital Hall Effects from Orbital Texture", Physical Review Letters 121, 086602 (2018)Go et al., "Orbital torque: Torque generation by orbital current injection", Physical Review Research 2, 013177 (2020)Hayashi et al., "Observation of long-range orbital transport and giant orbital torque", Communications physics 6, 32 (2023).

[0006] Spin current is a flow of spin angular momentum without accompanying electric charge, and can be widely used to control various spintronic devices. Because it does not involve electric charge, it does not generate Joule heat, which can significantly reduce the energy consumption of electronic devices. Furthermore, spin current can exert torque on magnetization more efficiently than an Oersted magnetic field. Spin current has the potential to dramatically improve the performance of electronic devices such as transistors, random access memories, and logic operation elements, which are currently facing the fundamental limits of performance enhancement due to miniaturization.

[0007] The generation of spin current is based on the spin-orbit interaction (SOI) that exists in materials. Conventionally, SOI is a material-specific phenomenon, and it is known to be large in rare metals with high atomic numbers, such as platinum, tantalum, tungsten, and bismuth. However, there is a risk of depletion of rare metals with high atomic numbers.

[0008] The present disclosure aims to provide a spintronic device, a magnetic memory, an electronic device, and a method for fabricating a spintronic device that can generate spin current using a material that is not likely to be depleted.

[0009] A spintronics device according to one embodiment includes a generator layer that generates a spin current and is composed of a mixture of Al and Si. The generator layer includes a region in which the Al and Si composition ratios are constant across the thickness of the generator layer, i.e., the variation in the Al and Si composition ratios across the thickness of the generator layer is within 20% of the average. Research by the inventors has shown that a large spin current can be generated by including a region in which the Al and Si composition ratio is constant across the thickness of the generator layer. Al is the third most abundant element in the Earth's crust, after oxygen (O) and silicon (Si), and is the most abundant element among metallic elements. Si is the second most abundant element in the Earth's crust, after oxygen (O), and is the most abundant element among semiconductors. Therefore, spin current can be generated using a material that is unlikely to be depleted.

[0010] A magnetic memory according to one embodiment includes the above-described spintronic device. By including the above-described spintronic device, the magnetic memory can generate a spin current using a material that is not likely to be depleted.

[0011] Another embodiment of a magnetic memory includes a first ferromagnetic layer, a non-magnetic layer disposed on the first ferromagnetic layer, a second ferromagnetic layer disposed on the non-magnetic layer, and a generator layer disposed on the second ferromagnetic layer and composed of a mixture of a metal material and a semiconductor material, for generating a spin current. The generator layer includes a region in which the Al and Si composition ratio is constant across the thickness of the generator layer, i.e., the variation in the Al and Si composition ratios across the thickness of the generator layer is within 20% of the average value. The magnetic memory stores information by controlling the magnetization direction of the second ferromagnetic layer using the spin current generated in the generator layer. This magnetic memory has the configuration of the spintronics device described above. Therefore, spin current can be generated using a material that is not likely to be depleted.

[0012] An electronic device according to one embodiment includes one or more of the magnetic memories described above. The electronic device has the spintronics device configuration described above. Therefore, a spin current can be generated using a material that is not likely to be depleted.

[0013] A method for fabricating a spintronic device according to one embodiment is a method for fabricating the above-described spintronic device, and includes the step of alternately depositing a plurality of Al layers and a plurality of Si layers by sputtering.

[0014] In this manufacturing method, a generated layer is formed by the intermixing of atoms of the Al layer and the Si layer during sputtering. The thickness of the generated layer depends on the total thickness of the Al layer and the Si layer. Therefore, a generated layer of any desired thickness can be easily formed. For example, a generated layer can also be formed by simultaneously depositing Si and Al. However, in this case, the sputtering apparatus must be equipped with two high-frequency power supplies and two plasma generating mechanisms for sputtering the target, which increases the size of the sputtering apparatus. In the above manufacturing method, Si and Al are deposited alternately, so the sputtering apparatus only needs to be equipped with one high-frequency power supply and one plasma generating mechanism for sputtering the target. Therefore, the sputtering apparatus can be made smaller.

[0015] In the above-described manufacturing method, the deposition step may alternately deposit three or more Si layers and three or more Al layers, which can favorably form a region in the generated layer where the Al / Si composition ratio is constant in the layer thickness direction.

[0016] In the above-described fabrication method, the thickness of each of the plurality of Si layers and the thickness of each of the plurality of Al layers may be less than 1 nm, in which case atoms of the Al layer and atoms of the Si layer are effectively mixed together, and the variation in the Al to Si composition ratio in the layer thickness direction can be further reduced.

[0017] According to the present disclosure, it is possible to provide a spintronics device, a magnetic memory, an electronic device, and a method for fabricating a spintronics device that can generate a spin current using a material that is not likely to be depleted.

[0018] Fig. 1 is a perspective view showing the configuration of a spintronics device according to a first embodiment of the present disclosure. Parts (a) and (b) of Fig. 2 are schematic diagrams showing an example of a method for fabricating a spintronics device. Parts (a) and (b) of Fig. 3 are schematic diagrams showing another example of a method for fabricating a spintronics device. Fig. 4 is a diagram showing the structure of a sample used in an experiment. Fig. 5 is a diagram showing a structure of a sample containing Si, Al, Ni, ０．９５ Cu ０．０５ , and SiO ２ FIG. 6 is a table showing the film formation conditions. FIG. 7 is a graph showing the composition distribution within the frame in FIG. 6. FIG. 8 is a schematic diagram showing a measurement system for spin torque ferromagnetic resonance (ST-FMR) method. FIG. 9 is a diagram showing a sample with an AC current applied. The plot shown in FIG. 10 is an example of the measurement results of the ST-FMR spectrum of a sample. FIG. 11 is a graph showing the results of evaluation by changing the AC current frequency within the range of 5 GHz to 10 GHz. FIG. 12 is a graph plotting the results of ST-FMR measurement of five samples fabricated with different ratios of Al layer thickness to Si layer thickness. FIG. 13 is a table showing the sample numbers, Al layer thicknesses, Si layer thicknesses, and the ratio of the Al layer thickness in the generated layer for five samples. FIG. 14 is a perspective view showing the configuration of a magnetic memory according to a second embodiment of the present disclosure. Parts (a) and (b) of FIG. 15 are cross-sectional views showing the configuration of a memory element.

[0019] Hereinafter, embodiments of a spintronics device, a magnetic memory, an electronic device, and a method for fabricating a spintronics device according to the present disclosure will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicated explanations will be omitted.

[0020] 1 is a perspective view showing the configuration of a spintronics device 1 (hereinafter simply referred to as device 1) according to a first embodiment of the present disclosure. As shown in FIG. 1, this device 1 includes a generation layer 4.

[0021] The generator layer 4 is a layered region. The generator layer 4 generates a spin current. The spin current is a flow of angular momentum of electrons, and may be an orbital current. The thickness of the generator layer 4 is, for example, greater than 1 nm and less than or equal to 100 nm. The generator layer 4 contains a mixture of Al and Si.

[0022] In the generated layer 4, the Al composition ratio and the Si composition ratio are constant in the layer thickness direction. Here, "constant composition ratio" means that the variation in the composition ratio is within 20% of the average value over a sufficient length range in the thickness direction. In the intermediate region, the Al composition ratio is, for example, in the range of 1% to 99%, and the Si composition ratio is, for example, in the range of 1% to 99%.

[0023] Parts (a) and (b) of FIG. 2 are schematic diagrams illustrating an example of a method for fabricating the device 1. First, as shown in part (a) of FIG. 2, a substrate 5 is prepared. Various substrates, such as a surface-oxidized Si substrate, can be used as the substrate 5. Next, the substrate 5 is placed in a sputtering apparatus, and an Al target is also placed in the sputtering apparatus. Then, as shown in part (b) of FIG. 2, Al is deposited on the substrate 5 by sputtering to form an Al layer 3a. Subsequently, a Si target is placed in the sputtering apparatus instead of the Al target, and Si is deposited on the Al layer 3a by sputtering to form a Si layer 2a. Thereafter, the deposition of the Al layer 3a and the deposition of the Si layer 2a are alternately repeated.

[0024] Parts (a) and (b) of Figure 3 are schematic diagrams showing another example of a method for fabricating the device 1. First, as shown in part (a) of Figure 3, a substrate 5 is prepared. Next, the substrate 5 is placed in a sputtering apparatus, and a Si target is also placed in the sputtering apparatus. Then, as shown in part (b) of Figure 3, Si is deposited on the substrate 5 by sputtering to form a Si layer 2a. Next, an Al target is placed in the sputtering apparatus again instead of the Si target, and Al is deposited on the Si layer 2a by sputtering to form an Al layer 3a. Thereafter, the deposition of the Si layer 2a and the deposition of the Al layer 3a are alternately repeated.

[0025] 2 and 3, the number of Si layers 2a and Al layers 3a may be 2 or more, and may be 3, 4, or 6 or more. In one embodiment, the number of Si layers 2a and Al layers 3a is 10.

[0026] In the examples shown in FIGS. 2 and 3 , the deposition thickness of each of the Si layer 2a and the Al layer 3a is, for example, 0.25 nm or more and less than 1.0 nm. Alternatively, the deposition thickness of each of the Si layer 2a and the Al layer 3a may be greater than 0 nm and less than 0.25 nm. In one example, the deposition thickness of the Si layer 2a is equal to the deposition thickness of the Al layer 3a. In another example, the deposition thickness of the Si layer 2a is different from the deposition thickness of the Al layer 3a. The thicknesses of the multiple Si layers 2a may be equal to each other, or at least one layer may have a thickness different from the other layers. The thicknesses of the multiple Al layers 3a may be equal to each other, or at least one layer may have a thickness different from the other layers.

[0027] In the examples shown in FIGS. 2 and 3 , when the Al layer 3a and the Si layer 2a are deposited by sputtering, material particles impinge forcefully onto the surface of the underlying layer. Due to the large kinetic energy of the particles, they mix with atoms of the underlying layer (the Si layer 2a for the Al layer 3a, and the Al layer 3a for the Si layer 2a). Therefore, in these examples, the Al layer 3a and the Si layer 2a do not form neat layers, and regions of mixed Si and Al are formed. This results in the formation of the generated layer 4. Because the materials constituting the Si layer 2a and the Al layer 3a are insoluble with each other, they do not diffuse atomically, and clumps of aggregated Si atoms and clumps of aggregated Al atoms may form, respectively. The device 1 is fabricated through the above steps. The substrate 5 used in each of the above fabrication methods may be removed from the device 1 as needed.

[0028] The effects achieved by the device 1 of this embodiment and its fabrication method, which have the above-described configuration, are now described. The device 1 of this embodiment includes a generation layer 4 composed of a mixture of Al and Si, which generates a spin current. The generation layer 4 includes a region in which the Al and Si composition ratios are constant, i.e., the variation in the Al and Si composition ratios across the thickness of the generation layer 4 is within 20% of the average. According to the inventor's research, the generation of a large spin current can be achieved by including a region in the generation layer 4 where the Al and Si composition ratios are constant across the thickness. The generation of the spin current in the generation layer 4 is likely based on spin-orbit interaction (SOI), but this is not yet clear. The spin current may also be an orbital current. Non-Patent Documents 7 and 8 disclose research on the generation of orbital current, i.e., the flow of electron orbital angular momentum due to orbital hybridization and inversion symmetry breaking in a crystal. Non-Patent Documents 9 and 10 disclose research on the effect of an orbital current injected into a ferromagnetic material exerting a torque on the magnetization via spin-orbit interaction.

[0029] Rare metals such as platinum, which have traditionally been thought to produce SOI, are in danger of becoming depleted, and therefore there is a need for spintronics devices that do not rely on rare metals such as platinum, which have traditionally been thought to produce SOI.

[0030] Al is the third most abundant element in the Earth's crust after oxygen (O) and silicon (Si), and is the most abundant element among metallic elements. Si is the second most abundant element in the Earth's crust after oxygen (O), and is the most abundant element among semiconductors. Therefore, according to the device 1 and its fabrication method of this embodiment, it is possible to generate spin current using a material that is not likely to be depleted.

[0031] The method for fabricating a spintronic device according to this embodiment includes alternately depositing multiple Al layers 3a and multiple Si layers 2a by sputtering. In this fabrication method, the generated layer 4 is formed by intermixing atoms of the Al layers 3a and the Si layers 2a during sputtering. The thickness of the generated layer 4 depends on the total thickness of the Al layers 3a and the Si layers 2a. Therefore, a generated layer 4 of any desired thickness can be easily formed. For example, the generated layer 4 can be formed by simultaneously depositing Si and Al. However, this requires the sputtering apparatus to have two high-frequency power supplies and two plasma generating mechanisms for sputtering the target, which increases the size of the sputtering apparatus. In the fabrication method according to this embodiment, because Si and Al are alternately deposited, the sputtering apparatus only needs to have one high-frequency power supply and one plasma generating mechanism for sputtering the target. This allows for a more compact sputtering apparatus.

[0032] As described above, three or more Si layers 2a and three or more Al layers 3a may be alternately deposited, which makes it possible to preferably form a region in the generated layer 4 where the composition ratio of Al to Si is constant in the layer thickness direction.

[0033] As described above, the thickness of each of the plurality of Si layers 2 a and the thickness of each of the plurality of Al layers 3 a may both be less than 1 nm, in which case the atoms of the Al layer 3 a and the atoms of the Si layer 2 a are effectively mixed together, and the variation in the Al to Si composition ratio in the generation layer 4 in the layer thickness direction can be further reduced.

[0034] [Example] An experiment conducted by the present inventor will be described. As shown in FIG. 4, the present inventor formed a Si layer 2 (thickness: 10 nm) on a surface-oxidized Si substrate (substrate 5), and then formed an Al layer 3a (thickness: t Ａｌ [nm]), 10 layers of Si layer 2a (thickness t Ｓｉ Nine layers of Ni ([nm]) were formed alternately. ０．９５ Cu ０．０５ Layer 6 (thickness 10 nm), and SiO ２ Layer 7 (thickness: 20 nm) was then formed. All of these layers were formed at room temperature using magnetron sputtering.０．９５ Cu ０．０５ Layer 6 is a spin current detection layer, made of SiO ２ Layer 7 is a cap layer for preventing oxidation. The Ar gas pressure during sputtering was 0.22 [Pa]. ０．９５ Cu ０．０５ , and SiO ２ The film deposition conditions (whether RF or DC was used, sputtering power, and deposition rate) were then subjected to photolithography and lift-off processes to fabricate thin wire-shaped samples with a width of 5 μm and a length of 100 μm.

[0035] FIG. 6 is a scanning transmission electron microscope (STEM) image taken by high-angle annular dark field (HAADF) and showing an enlarged cross section of the fabricated sample. FIG. 7 is a graph showing the composition distribution of Si, Al, Ni, Cu, and O (oxygen) in the thickness direction obtained by energy dispersive X-ray spectroscopy (EDS) of the area within the frame 40 in FIG. 6 . In the graph of FIG. 7 , the horizontal axis represents the position in the thickness direction (nm), and the vertical axis represents the atomic concentration (atomic %). In FIG. 7 , line G1 represents the analysis result of the Si concentration, line G2 represents the analysis result of the Al concentration, line G3 represents the analysis result of the Ni concentration, line G4 represents the analysis result of the Cu concentration, and line G5 represents the analysis result of the O concentration.

[0036] Referring to FIG. 7, it can be seen that Al and Si are mixed at the atomic level in the portion where the Al layers 3a and Si layers 2a are alternately stacked, i.e., in the generated layer 4 (area D1 in the figure). This is thought to be due to the high kinetic energy of the sputtered particles under the sputtering conditions of this example, which resulted in interfacial mixing when the different materials were stacked. From these results, it can be predicted that even when two or more Al layers 3a and two or more Si layers 2a are alternately stacked, the Al of the Al layer 3a and the Si of the Si layer 2a will mix at the atomic level within the stacked structure, forming Si-Al nanocrystals. Since Si and Al are immiscible, they separate in thermal equilibrium. However, in vapor phase growth methods such as sputtering, the plasma state (gas) is rapidly cooled on the deposition substrate to form a film (solid). This results in the realization of crystals with composition ratios that do not exist in the thermal equilibrium phase diagram (metastable state). The thickness t of the Al layer 3a Ａｌ and the thickness t of the Si layer 2a Ｓｉ By adjusting the ratio of Si and Al, the composition ratio of the Si-Al nanocrystals can be set to any ratio. It can also be confirmed that the Al composition ratio and Si composition ratio of the generated layer 4 are constant in the layer thickness direction over a thickness range of 8 nm. The inventors also prepared a sample in which the generated layer 4 was formed by simultaneously sputtering Si and Al, and performed similar observations on that sample. It was then confirmed that the Al composition ratio and Si composition ratio of the generated layer 4 were also constant in the layer thickness direction in that sample.

[0037] In order to obtain Si-Al nanocrystals in which Si and Al are uniformly mixed on a nanoscale, the thickness t Ａｌ and the thickness t of the Si layer 2a Ｓｉ It is preferable that the thickness is less than 1 nm.

[0038] FIG. 8 is a schematic diagram showing a measurement system for spin torque ferromagnetic resonance (ST-FMR) to evaluate the spin current generation efficiency of Si—Al nanocrystals. This measurement system includes a substrate 10 on which a sample S is mounted, an AC current source (signal generator) 11, a bias tee circuit 12, and a voltmeter 13. Conductive films 10a to 10c constituting a coplanar waveguide are formed on the surface of the substrate 10. The conductive films 10a and 10c are electrically shorted to one end of the sample S in the longitudinal direction (x direction). The conductive film 10b is electrically shorted to the other end of the sample S in the longitudinal direction. The conductive films 10a and 10c are connected to the reference potential line (ground potential line) of this circuit. The conductive film 10b is connected to a node 121 of the bias tee circuit 12. The bias tee circuit 12 includes a capacitor 122 having one end connected to the node 121 and the other end connected to the AC current source 11, and an inductor 123 having one end connected to the node 121 and the other end connected to the voltmeter 13. The AC current source 11 has one end connected to the capacitor 122 and the other end connected to a reference potential line (ground potential line), and an AC current j is supplied via the capacitor 122. ａｃ The voltmeter 13 has one end connected to the inductor 123 and the other end connected to a reference potential line (ground potential line), and measures the voltage generated between the conductive films 10a, 10c and the conductive film 10b. Figure 8 shows an orthogonal coordinate system consisting of the x direction, which is the longitudinal direction of the strip-shaped sample S, and the y direction, which is the transverse direction, and the angle θ ｍ Furthermore, in FIG. 8, the AC current j ａｃ An arrow indicating the

[0039] In this example, first, SiO 2 was formed on both ends of the fabricated thin-line sample S by Ar ion milling in order to ensure electrical contact with the electrodes. ２ The layer 7 was cut. Then, a microwave with a power of 20 dBm and a frequency of 8 GHz was output from the AC current source 11, and an AC current j was applied to the sample. ａｃ The magnitude of the DC voltage was measured by the voltmeter 13 while sweeping the external magnetic field B between 0 T and 0.2 T. All measurements were carried out at room temperature.

[0040] FIG. 9 shows the AC current j ａｃ1 is a diagram showing sample S in a state where a voltage is applied. ０．９５ Cu ０．０５ The AC current j flowing through the generating layer 4 of the sample S having the layer 6 (ferromagnetic layer FM) ａｃ is the spin current j in the generation layer 4. Ｓ and the Ni which is the spin current detection layer ０．９５ Cu ０．０５ To layer 6, polarization σ ｓ Spin current j with Ｓ is injected. Then, the ferromagnetic Ni ０．９５ Cu ０．０５ The magnetization m of the layer 6 is subjected to an Oersted magnetic field h generated according to Ampere's law. Ｏｅ and spin current j Ｓ Two types of torques, which are generated by both the AC current j and the magnetic field j, act on the magnetic field j, and ferromagnetic resonance FMR is excited. ａｃ The resistance of the sample S changes over time due to the anisotropic magnetoresistance effect, in which the resistance changes depending on the relative angle between the magnetization m and the applied AC current j. ａｃ A DC voltage due to the spin current j appears across the sample S, resulting from the rectification effect caused by the change in resistance. By measuring the magnitude of this rectified voltage, a ferromagnetic resonance spectrum can be obtained. In the spectrum obtained by the ST-FMR method, the spin current j Ｓ , and the torque due to the Oersted magnetic field B contribute separately to the symmetric Lorentzian function and the antisymmetric Lorentzian function, respectively. Therefore, from the analysis of the obtained spectrum, the spin current j Ｓ This allows for the detection and evaluation of

[0041] The plot shown in FIG. 10 is for the case where the number of stacked Al layers 3a and Si layers 2a is 10 (i.e., n=10), and the thickness t Ａｌ is 0.4 nm, and the thickness t Ｓｉ10 is an example of the measurement results of the ST-FMR spectrum of sample S with a spin current j of 0.6 nm. In FIG. 10, the horizontal axis indicates the external magnetic field (mT), and the vertical axis indicates the magnitude of the DC voltage (μV). The dashed line in FIG. 10 indicates the fitting result by adding together the symmetric Lorentzian function and the antisymmetric Lorentzian function, which reproduces the experimental results well. Referring to the figure, the symmetric Lorentzian function component appears larger than the antisymmetric Lorentzian function component. This is because the spin current j Ｓ This shows that a large torque resulting from the above is generated in sample S.

[0042] The index that represents the efficiency of conversion from current to spin torque is called the spin torque efficiency, and the spin torque efficiency ξ ＦＭＲ is given by the following equation (1). Here, V ｓ is the amplitude of the symmetric spectrum, and V ａ is the amplitude of the antisymmetric spectrum, and B ｒ is the resonant magnetic field. These amplitudes V ｓ , amplitude V ａ , and the resonant magnetic field B ｒ is obtained from spectral fitting, e is the elementary charge, and μ ０ is the magnetic permeability of vacuum, and h is the Dirac constant (reduced Planck constant). ０ M ｓ is the saturation magnetization of the ferromagnetic layer FM, and d Ｆ is the thickness of the ferromagnetic layer FM, and d Ｎ is the thickness of the spin current generation layer (i.e., generation layer 4).

[0043] FIG. 11 shows that the number of stacked Al layers 3a and Si layers 2a is 10, and the thickness of the Al layer 3a is t Ａｌ and the thickness t of the Si layer 2a Ｓｉ For sample S, where both are 0.5 nm, the AC current j ａｃ 11 is a graph showing the results of evaluations performed by varying the frequency in the range of 5 GHz to 10 GHz. In FIG. 11, the horizontal axis represents frequency (GHz) and the vertical axis represents spin torque efficiency ξ ＦＭＲ Here, the resonant magnetic field B ｒ The saturation magnetization μ estimated from the frequency dependence of ０ Mｓ (=0.32T), the design thickness of the spin current detection layer d Ｆ (=10 nm), and the designed thickness of the spin current generating layer d Ｎ (=10.5 nm) was used for the evaluation. Referring to FIG. 11, the spin torque efficiency ξ ＦＭＲ There is almost no change in the spin torque efficiency ξ ＦＭＲ The average value of 0.54 was obtained for a 10 nm thick Al layer and a 10 nm thick Ni layer. ０．９５ Cu ０．０５ Spin torque efficiency ξ obtained by stacking layers ＦＭＲ (=0.01). Therefore, this result indicates that the spin torque efficiency ξ ＦＭＲ This shows that the spin torque efficiency ξ ＦＭＲ is made of Pt and Ni, which are typical conventional spin current generating materials. ０．９５ Cu ０．０５ The spin torque efficiency ξ obtained by stacking ＦＭＲ (=0.07). Therefore, it can be said that the structure in which the Si layers 2a and the Al layers 3a are alternately stacked is a spin current generating structure that is useful for application to devices.

[0044] FIG. 12 shows the thickness t Ａｌ and the thickness t of the Si layer 2a Ｓｉ 12 is a graph plotting the results of ST-FMR measurements of five samples S prepared with different ratios of the thickness of the Al layer 3a in the generated layer 4. Ａｌ (R Ａｌ = t Ａｌ / (t Ａｌ +t Ｓｉ ) × 100). The vertical axis of FIG. 12 represents the spin torque efficiency ξ ＦＭＲ 13 shows the magnitude of the thickness t Ａｌ , thickness t Ｓｉ , the thickness ratio R of the Al layer 3 a in the generated layer 4 Ａｌ The number of stacked Al layers 3a and Si layers 2a is 10. Referring to these graphs and tables, the ratio R ＡｌIn the range of 13% to 50%, the spin torque efficiency ξ ＦＭＲ As a result, the spin torque efficiency ξ ＦＭＲ To improve the ratio R Ａｌ exists.

[0045] Second Embodiment Fig. 14 is a perspective view showing the configuration of a magnetic memory 30 according to a second embodiment of the present disclosure. The magnetic memory 30 is a magnetic random access memory and includes the device 1 according to the first embodiment. Specifically, the magnetic memory 30 includes memory elements (memory cells) M arranged in a matrix in the row direction (s direction) and column direction (t direction). １，１ ~M Ｉ，Ｊ The figure shows a representative memory element M ｉ，ｊ , M ｉ，（ｊ＋１） , M （ｉ＋１），ｊ , M （ｉ＋１），（ｊ＋１） are shown (i=1, 2, . . . , I-1, j=1, 2, . . . , J-1).

[0046] Part (a) of FIG. 15 shows the memory element M ｉ，ｊ 1 is a cross-sectional view showing the configuration of a memory element M. ｉ，ｊ The present embodiment is a giant magnetoresistance (GMR) element or a tunnel magnetoresistance (TMR) element, and includes a first ferromagnetic layer (fixed layer) 31, a nonmagnetic layer 32 provided on the ferromagnetic layer 31, a second ferromagnetic layer (movable layer) 33 provided on the nonmagnetic layer 32, an Al layer 3 provided on the ferromagnetic layer 33, a generator layer 4 serving as a device 1 provided on the Al layer 3, and a Si layer 2 provided on the generator layer 4. The generator layer 4 has the same configuration as in the first embodiment. A spin current is generated in the generator layer 4. A pair of electrodes 35 and 36 are disposed on the Al layer 3. The electrodes 35 and 36 are spaced apart from each other. An electrode 37 is disposed below the ferromagnetic layer 31.

[0047] Another memory element M shown in FIG. ｉ，（ｊ＋１） , M （ｉ＋１），ｊ , M （ｉ＋１），（ｊ＋１） is also the memory element M shown in part (a) of FIG. ｉ，ｊ The element is a GMR element or a TMR element having a similar structure to that described above.

[0048] The memory element M shown in part (a) of FIG. ｉ，ｊ The relative magnetization M of the ferromagnetic layers 31 and 33 is １ , M ２ The ferromagnetic layers 31 and 33 are made of, for example, NiFe. The ferromagnetic layers 31 and 33 may be made of different materials or the same material. The magnetization M of the ferromagnetic layer 31 １ is fixed, and the magnetization M ２ The material of the non-magnetic layer 32 may be a non-magnetic metal such as Cu, or may be aluminum oxide (Al ２ O ３ Insulators such as silicon dioxide (SiO 2 ) and magnesium oxide (MgO) can also be used.

[0049] Referring again to FIG. 14, the j-th row has a word line WL ｊ are arranged in the (j+1)th row, and the word line WL ｊ＋１ In the i-th column, three bit lines BLA are arranged. ｉ , BLB ｉ , BLC ｉ are arranged, and three bit lines BLA are arranged in the (i+1)th column. ｉ＋１ , BLB ｉ＋１ , BLC ｉ＋１ In this way, at least one word line is provided for each row, and at least three bit lines are provided for each column. ｉ，ｊ , M ｉ，（ｊ＋１） , M （ｉ＋１），ｊ , M （ｉ＋１），（ｊ＋１） A pair of select transistors STA and STB is connected to the i-th column of memory elements M. One current terminal of the select transistor STA is connected to an electrode 35, and one current terminal of the select transistor STB is connected to an electrode 36. ｉ，ｊ , M ｉ，（ｊ＋１） The other current terminals of the select transistors STA and STB connected to the bit line BLA are ｉ , BLB ｉ The (i+1)th column memory element M （ｉ＋１），ｊ , M （ｉ＋１），（ｊ＋１） The other current terminals of the select transistors STA and STB connected to the bit line BLA areｉ＋１ , BLB ｉ＋１ The jth row memory element M ｉ，ｊ , M （ｉ＋１），ｊ Select transistor STA connected to ， Each control terminal of the STB is connected to a word line WL ｊ The memory element M in the (j+1)th row is connected to ｉ，（ｊ＋１） , M （ｉ＋１），（ｊ＋１） Select transistor STA connected to ， Each control terminal of the STB is connected to a word line WL ｊ＋１ is connected to.

[0050] The memory element M of the i-th column ｉ，ｊ , M ｉ，（ｊ＋１） The electrode 37 is connected to the bit line BLC ｉ The (i+1)th column memory element M （ｉ＋１），ｊ , M （ｉ＋１），（ｊ＋１） The electrode 37 is connected to the bit line BLC ｉ＋１ The word line WL is connected to ｊ , W.L. ｊ＋１ , bit line BLA ｉ , B.L.A. ｉ＋１ , BLB ｉ , BLB ｉ＋１ , BLC ｉ , and BLC ｉ＋１ is connected to a control circuit (not shown).

[0051] Memory element M ｉ，ｊ , M ｉ，（ｊ＋１） , M （ｉ＋１），ｊ , M （ｉ＋１），（ｊ＋１） When writing to the selected memory element (here, memory element M ｉ，ｊ The word line WL corresponding to ｊ through the select transistor STA of the row ， STB is turned on, and the bit line BLA of the corresponding column ｉ , BLB ｉ By passing a current between the electrodes 35 and 36 through ｉ，ｊ The spin current J ｓ This spin current J ｓ is the magnetization M of the ferromagnetic layer 33. ２ interacts with the magnetization M ２As a result, the magnetization M of the ferromagnetic layer 33 ２ is inverted.

[0052] Memory element M ｉ，ｊ , M ｉ，（ｊ＋１） , M （ｉ＋１），ｊ , M （ｉ＋１），（ｊ＋１） The memory cell reads information by utilizing the GMR effect or the TMR effect. ｉ，ｊ The word line WL corresponding to ｊ through the select transistor STA of the row ， STB is turned on, and the bit line BLA of the corresponding column ｉ , BLB ｉ , BLC ｉ 15A, when the magnetizations of the ferromagnetic layers 31 and 33 are parallel, the vertical current path passing through the ferromagnetic layer 31, the non-magnetic layer 32, and the ferromagnetic layer 33 has a relatively low resistance, and the bit line BLA ｉ , BLB ｉ , BLC ｉ 15B, when the magnetization direction of the ferromagnetic layer 33 is reversed and the magnetizations of the ferromagnetic layers 31 and 33 are antiparallel, the vertical current path passing through the ferromagnetic layer 31, the nonmagnetic layer 32, and the ferromagnetic layer 33 has a relatively high resistance, and the bit line BLA ｉ , BLB ｉ , BLC ｉ For example, "0" is read out via

[0053] According to the magnetic memory 30 of this embodiment, a spin current is generated by the generation layer 4 (device 1), which is capable of generating a spin current using a material that is not likely to be depleted, and this spin current interacts with the magnetization of the ferromagnetic layer 33, thereby controlling the magnetization direction of the ferromagnetic layer 33.

[0054] The magnetic memory 30 of this embodiment can be applied to various electronic devices. That is, an electronic device may be equipped with one or more magnetic memories 30. Examples of electronic devices include a memory board equipped with multiple magnetic memories 30, an electronic component equipped with multiple magnetic memories 30 or memory boards, a home appliance equipped with a magnetic memory 30, a memory board, or an electronic component, a personal computer, a smartphone, an in-vehicle device, a measuring device, a control device, and other devices that require memory.

[0055] According to the magnetic memory 30 of this embodiment, the following new effects can be achieved.

[0056] The efficiency of spin current generation due to the spin Hall effect resulting from spin-orbit interaction (SOI) is given by the spin Hall conductivity σ ＳＨ Just as the current density is obtained by multiplying the voltage V by the electrical conductivity σ (Ohm's law), the current density can be obtained by multiplying the voltage V by the spin Hall conductivity σ ＳＨ The voltage V required to generate the spin current required for bit rewriting in magnetic memory is multiplied by the spin Hall conductivity σ ＳＨ The larger the voltage, the smaller the energy consumption of the bit rewrite. Since the energy consumption of the bit rewrite is proportional to the square of the voltage V, the spin Hall conductivity σ ＳＨ The larger the value, the smaller the energy consumption of bit rewriting can be.

[0057] In general, in metals such as Cu and Ag, which have a large electrical conductivity σ, the spin Hall conductivity σ ＳＨ is small. Spin Hall conductivity σ ＳＨ The electrical conductivity σ of topological insulators such as BiSb, which has a large electrical conductivity σ, is small. If a material with a small electrical conductivity σ is used as the spin current source of a magnetic memory, the wiring resistance of each bit of the magnetic memory increases, causing signal delay and attenuation, signal waveform distortion, increased power consumption, electromagnetic wave radiation, and the like, which hinders high-speed and energy-saving operation. In contrast, in this embodiment, materials such as Al and Si, which have a large electrical conductivity σ but a material-specific spin Hall conductivity σ, are used. ＳＨ A large spin current can be generated using a material with a small spin current.

[0058] The spintronic devices, magnetic memories, electronic devices, and methods for fabricating spintronic devices according to the present invention are not limited to the above-described embodiments and may be modified in various ways. While preferred embodiments of the present invention have been described in detail, the present invention is not limited to these specific embodiments. In other words, these are merely a selection of numerous examples of the present invention, and it goes without saying that various modifications and variations are possible within the scope of achieving the objectives, objectives, and effects of the present invention, even if not directly described in the examples. In particular, the combinations of multiple components or functions described in the examples may be modified (added or deleted).

[0059] The problems and objectives of the present invention are generally described in the "Problems to be Solved by the Invention" section, but are not limited thereto, and it goes without saying that the problems and objectives described in the examples are also valid for each invention. The effects described in the examples are the reverse of the problems or objectives, so their existence should be understood even if the problems or objectives are not directly described there.

[0060] Although the examples describe inventions for achieving a problem or purpose, the degree of achievement does not necessarily have to be 100%; it varies depending on the combination of the invention's components. It goes without saying that an invention should not be rejected on the grounds that it does not achieve its purpose, even if it achieves only 10% of its purpose.

[0061] 1...spintronic device, 2, 2a...Si layer, 3, 3a...Al layer, 4...generation layer, 5...substrate, 6...Ni ０．９５ Cu ０．０５ layer, 7...SiO ２ Layer, 10...substrate, 10a to 10c...conductive films, 11...AC current source, 12...bias tee circuit, 13...voltmeter, 30...magnetic memory, 31...ferromagnetic layer, 32...non-magnetic layer, 33...ferromagnetic layer, 35, 36, 37...electrodes, 121...node, 122...capacitor, 123...inductor, B...external magnetic field, B ｒ ...resonant magnetic field, FM...ferromagnetic layer, FMR...ferromagnetic resonance, NM...nonmagnetic layer, h Ｏｅ ...Oersted magnetic field, jａｃ ...alternating current, j Ｓ ...spin current, m...magnetization, S...sample, STA, STB...selection transistor, θ ｍ …angle, σ ｓ …polarization.

Claims

1. A spintronics device comprising a generation layer that generates spin current and is composed of a mixture of Al and Si, the generation layer including a region in which the variation in the composition ratio of Al and Si in the thickness direction of the generation layer is within 20% of the average value of each.

2. A magnetic memory comprising the spintronics device according to claim 1.

3. A magnetic memory comprising: a first ferromagnetic layer; a non-magnetic layer provided on the first ferromagnetic layer; a second ferromagnetic layer provided on the non-magnetic layer; and a generation layer provided on the second ferromagnetic layer and comprising a mixture of Al and Si, for generating a spin current; wherein the generation layer includes a region in which the variation in the composition ratios of Al and Si in the thickness direction of the generation layer is within 20% of their respective average values; and wherein information is stored by controlling the orientation of magnetization of the second ferromagnetic layer using the spin current generated in the generation layer.

4. An electronic device equipped with one or more magnetic memories according to claim 2 or 3.

5. A method for fabricating the spintronic device according to claim 1, comprising the step of alternately depositing a plurality of Al layers and a plurality of Si layers by sputtering.

6. The method for producing a spintronics device according to claim 5, wherein in the depositing step, three or more Al layers and three or more Si layers are alternately deposited.

7. A method for producing a spintronic device according to claim 5 or 6, wherein the thickness of each of the plurality of Al layers and the thickness of each of the plurality of Si layers are both less than 1 nm.

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