Spin devices

Abstract

We will realize a more efficient spin-current-to-electric current conversion element using a ferromagnetic material containing Sr, Ru, and O. The spin element is configured with a conversion layer 101 and a spin current generation layer 102, and the conversion layer 101 is made of (Sr 1-X A X ) x (Ru 1-Y B Y ) y O 3-z The conversion layer 101 is made of a ferromagnetic material with a perovskite structure (single crystal or polycrystalline) containing Sr, Ru, and O (0≦x≦0.05, 0≦y≦0.05, 0.9≦x≦1.1, 0.9≦y≦1.1, -0.1≦z≦0.1, A is an alkaline earth metal, B is a transition metal). For example, the conversion layer 101 is made of SrRuO3 with a composition deviation from the stoichiometric composition of 10% or less.

Description

[Technical Field]

[0001] The present invention relates to a spin element. [Background technology]

[0002] Perovskite-structured Sr x Ru y O 3-z (0.7≦x≦1.3, 0.7≦y≦1.3, -1≦z≦1) is a substance that is widely used as an electrode material in oxide-based electronics applications (MOSFETs, LEDs, DRAMs, etc.) due to its high chemical stability, high electrical conductivity, and high compatibility with oxides (perovskite oxides) such as SrTiO3 (Non-Patent Documents 1, 2, 3, Patent Document 1). x Ru y O 3-z is the Curie temperature (T C ) is also a ferromagnetic material with a maximum temperature of 169 K, and exhibits a tunnel magnetoresistance effect (Non-Patent Document 4).

[0003] For this reason, Sr x Ru y O 3-z This material is expected to be applied to magnetoresistive memories (hard disk drive (HDD) heads and magnetic random access memories (MRAM)) that use the tunnel magnetoresistive effect for read operations. Furthermore, because it is a material that allows current control of the magnetization direction using spin transfer torque, it is also possible to write to magnetoresistive memories (Non-Patent Document 5).

[0004] As mentioned above, Sr x Ru y O 3-z is a highly promising material for spin electronics applications (magnetoresistive memory, spin MOSFET, etc.) (Non-Patent Document 6). x Ru y O 3-z Spin current-electric current conversion using ZnO has also been reported (Non-Patent Document 7), and it is expected to be used not only as an electrode material or ferromagnetic material but also as a spin current-electric current conversion element.

[0005] If highly efficient spin-current-to-electric current conversion becomes possible, it will be possible to control the magnetization direction (corresponding to the write operation in magnetoresistive memory) with lower power consumption than in conventional magnetoresistive memory. Furthermore, highly efficient spin-to-electric current conversion is important for obtaining high output voltages in magnetoelectric spin orbital logic devices and spin Seebeck power generation devices (Non-Patent Document 8, Non-Patent Document 9). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7332033 [Non-patent literature]

[0007] [Non-Patent Document 1] HY Hwang, Y. Iwasa, M. Kawasaki, B. Keimer, N. Nagaosa and Y. Tokura, "Emergent phenomena at oxide interfaces", Nature Materials 11, 103 (2012). [Non-patent document 2] D. Popescu, B. Popescu, G. Jegert, S. Schmelzer, U. Boettger and P. Lugli, "Feasibility Study of SrRuO3 / SrTiO3 / SrRuO3 Thin Film Capacitors in DRAM Applications", IEEE Transactions on Electron Devices 61, 2130 (2014). [Non-patent document 3] B. Kim, B. Na, Y. Kwon, M. Jeong, Y. Kim, H. Lim and E. Yoon, "Effects of the flux-controlled cation off-stoichiometry in SrRuO3 grown by molecular beam epitaxy on its physical and electrical properties", Materials Letters 281, 128375 (2020). [Non-Patent Document 4] D. C. Worledge and T. H. Geballe, "Negative Spin-Polarization of SrRuO3", Physcal Review Letters 85, 5182 (2000). [Non-Patent Document 5] L. Liu, Q. Qin, W. Lin, C. Li, Q. Xie, S. He, X. Shu, C. Zhou, Z. Lim, J. Yu, W. Lu, M. Li, X. Yan, S. J. Pennycook and J. Chen, "Current-induced magnetization switching in all-oxide heterostructures", Nature Nanotechnology 14, 939 (2019). [Non-Patent Document 6] S. Sugahara and M. Tanaka, "A spin metal-oxide-semiconductor field-effect transistor using half-metallic-ferromagnet contacts for the source and drain", Applied Physics Letters 84, 2307 (2004). [Non-Patent Document 7] M. Wahler, N. Homonnay, T. Richter, A. Muller, C. Eisenschmidt, B. Fuhrmann and G. Schmidt, "Inverse spin Hall effect in a complex ferromagnetic oxide heterostructure", Scientific Reports 6, 28727 (2016). [Non-Patent Document 8] S. Manipatruni, D. E. Nikonov, C.-C. Lin, T. A. Gosavi, H. Liu, B. Prasad, Y.-L. Huang, E. Bonturim, R. Ramesh and I. A. Young, "Scalable energy-efficient magnetoelectric spin-orbit logic", Nature 565, 35 (2019). [Non-Patent Document 9] A. Kirihara, K. Kondo, M. Ishida, K. Ihara, Y. Iwasaki, H. Someya, A. Matsuba, K. Uchida, E. Saitoh, N. Yamamoto, S. Kohmoto and T. Murakami, "Flexible heat-flow sensing sheets based on the longitudinal spin Seebeck effect using one-dimensional spin-current conducting films", Scientific Reports 6, 23114 (2016). [Summary of the Invention] [Problems to be Solved by the Invention]

[0008] Existing, Sr x Ru y O 3-zIn the spin-current-to-electric current conversion element using SHE ) and spin Hall conductivity (σ SHE ) at room temperature are 0.035 and 1×10 4 A highly efficient spin-current-to-electrical current conversion element exceeding {(h / 2π) / e}S / m (h is Planck's constant) has not yet been realized. SHE ), spin Hall conductivity (σ SHE ) is 0.035, 1×10 4 The challenge is to realize a highly efficient spin-current-to-electric current conversion element exceeding {(h / 2π) / e}S / m.

[0009] The present invention has been made to solve the above problems, and aims to realize a more efficient spin-current-to-electric current conversion element using a ferromagnetic material containing Sr, Ru, and O. [Means for solving the problem]

[0010] The spin element according to the present invention is 1-X A X ) x (Ru 1-Y B Y ) y O 3-z The device comprises a conversion layer having an inverse spin Hall effect and made of a ferromagnetic material with a perovskite structure (0≦X≦0.05, 0≦Y≦0.05, 0.9≦x≦1.1, 0.9≦y≦1.1, -0.1≦z≦0.1, A is an alkaline earth metal, B is a transition metal), and a spin current generation layer made of a ferromagnetic material formed on the conversion layer. [Effects of the Invention]

[0011] As described above, according to the present invention, the conversion layer having the inverse spin-Hall effect is formed by using (Sr 1-X A X ) x (Ru 1-Y B Y ) y O 3-z(0≦X≦0.05, 0≦Y≦0.05, 0.9≦x≦1.1, 0.9≦y≦1.1, -0.1≦z≦0.1, A is an alkaline earth metal, B is a transition metal), which makes it possible to realize a more efficient spin-current-to-electric current conversion element using a ferromagnetic material containing Sr, Ru, and O. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view showing a partial configuration of a spin element according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing the crystal structure of SrRuO3. [Figure 3] FIG. 3 is a perspective view showing the configuration of a typical spin element (spin current-electric current conversion element) according to an embodiment of the present invention. [Figure 4] FIG. 4 is a characteristic diagram showing a change in voltage between the first electrode 103 and the second electrode 104 due to spin current-electric current conversion in the spin current generation layer 102 at 300K. [Figure 5] FIG. 5 is a characteristic diagram showing the first-order differentiation of microwave absorption occurring during ferromagnetic resonance in the spin current generation layer 102 at 300K with respect to an applied external magnetic field. [Figure 6] FIG. 6 is a diagram showing the configuration of another spin element according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] A spin element according to an embodiment of the present invention will be described below with reference to Fig. 1. This spin element includes a conversion layer 101 and a spin current generation layer .

[0014] The conversion layer 101 is made of a ferromagnetic material with a perovskite structure (single crystal or polycrystalline) containing Sr, Ru, and O, and has the inverse spin Hall effect. The conversion layer 101 is a spin current-to-electric current conversion layer that converts spin current and electric current. The spin current generation layer 102 is made of a ferromagnetic material and is formed on the conversion layer 101. For example, a spin element can be formed by forming the conversion layer 101 on the substrate 111 (crystal growth) and then forming the spin current generation layer 102 on the conversion layer 101 (crystal growth).

[0015] The conversion layer 101 is made of (Sr 1-X A X ) x (Ru 1-Y B Y ) y O 3-z (0≦X≦0.05, 0≦Y≦0.05, 0.9≦x≦1.1, 0.9≦y≦1.1, −0.1≦z≦0.1, A is an alkaline earth metal, and B is a transition metal).

[0016] For example, the conversion layer 101 can be made of SrRuO3 with a composition deviation of 10% or less from the stoichiometric composition. x Ru y O 3-z This means that (0.9≦x≦1.1, 0.9≦y≦1.1, -0.1≦z≦0.1).

[0017] The substrate 111 can be made of a crystal whose main surface on which the conversion layer 101 is formed is a cubic (001) plane or a pseudo-cubic (001) plane. The substrate 111 can be made of, for example, SrTiO3, MgO, (La 0.3 Sr 0.7 )(Al 0.65 Ta 0.35 It can be composed of any of the following crystals: O3, KTaO3, DyScO3, TbScO3, GdScO3, SmScO3, NdScO3, PrScO3, or Si.

[0018] The spin current generating layer 102 is, for example, La 0.67 Sr 0.33The spin current generating layer 102 can be made of MnO3. The spin current generating layer 102 can be made of Fe, Co, Ni, permalloy, Y3Fe5O 12 It can be made of a ferromagnetic material such as

[0019] Figure 2 shows the Sr x Ru y O 3-z The crystal structure of the conversion layer 101 is shown in Fig. 1. The deviation of the composition of Sr, Ru, and O from the ideal stoichiometric ratio of 1:1:3 is within 10%. x Ru y O 3-z By using the spin Hall angle (θ SHE ) exceeds 0.035, and the spin Hall conductivity (σ SHE ) but 1×10 4 It is possible to realize a spin-current-to-electric current conversion element with a spin current exceeding {(h / 2π) / e}S / m.

[0020] Sr x Ru y O 3-z Since Sr has a perovskite structure, it has the advantage of being easier to incorporate into heterostructures made of oxides compared to spin-current-to-electrical current conversion elements that do not have a perovskite structure, such as those made of Bi or Pd (References 1 and 2). Furthermore, by realizing a heterostructure, it has the advantage of being able to transmit spin current without loss. x Ru y O 3-z has the advantage that it can be epitaxially grown on Si(001) or Ge(001) substrates, making it easy to integrate on silicon wafers.

[0021] Figure 3 shows the structure of a typical spin element (spin current-to-electric current conversion element). A first electrode 103 and a second electrode 104 are formed spaced apart on the surface of a spin current generation layer 102. In this state, a microwave magnetic field of a certain frequency is irradiated, and an external magnetic field H is applied to induce ferromagnetic resonance in the spin current generation layer 102, causing a spin current J to flow in the conversion layer 101. s This spin current J sHowever, the inverse spin Hall effect in the conversion layer 101 causes a current J c The converted current J c is detected as a voltage between the first electrode 103 and the second electrode 104.

[0022] Next, we will explain the spin element that was actually fabricated. The substrate 111 was made of SrTiO3 (001), and the conversion layer 101 was fabricated by molecular beam epitaxy. In the film formation chamber of the film formation device, the substrate temperature was set to 780°C, and atomic beams of Sr and Ru were irradiated at 1000 K to achieve a predetermined composition ratio. -6 The conversion layer 101 was formed by growing SrRuO3 on the substrate 111 under an active oxygen atmosphere of about Torr. x Ru y O 3-z As long as the deviation in the thin film composition is within 10%, highly efficient spin-current-to-electric current conversion elements can be fabricated regardless of the substrate material or growth method.

[0023] Sr constituting the conversion layer 101 x Ru y O 3-z The composition ratio of Sr, Ru, and O in the SiO2 can be set to the value that maximizes the spin Hall angle. Here, the spin Hall angle indicates the conversion efficiency between spin current and electric current, and is given by the ratio of spin current to electric current. The value of the spin Hall angle can be calculated by the ratio of Sr with arbitrary values ​​of x, y, and z. x Ru y O 3-z can be obtained by numerical calculations using density functional theory for

[0024] The composition of the conversion layer 101 is evaluated by, for example, energy dispersive X-ray spectroscopy. x Ru y O 3-z As long as the deviation in composition is within 10%, the conversion layer 101 may be a single crystal or polycrystal of SrRuO3. As a growth method other than molecular beam epitaxy, for example, sputtering or pulsed laser ablation can be used. After the conversion layer 101 is formed (grown) as described above, La is deposited on the conversion layer 101. 0.67 Sr0.33 A film of MnO3 was formed as the spin current generation layer 102. In the film formation chamber of the above-mentioned film formation apparatus, the substrate temperature was set to 720°C, and atomic beams of La, Sr, and Mn were introduced at 1000 sieves to obtain a predetermined composition ratio. -6 The conversion layer 101 is supplied under an active oxygen atmosphere of about Torr. 0.67 Sr 0.33 MnO3 was grown to form the spin current generation layer 102. The spin current generation layer 102 may be either single crystal or polycrystalline.

[0025] To determine the spin Hall angle, a method called spin pumping can be used. Ferromagnetic resonance occurs when a ferromagnetic material is irradiated with a microwave magnetic field of a certain frequency and then an external magnetic field is swept. Spin pumping is the injection of spin current from the ferromagnetic material into an adjacent non-magnetic material during ferromagnetic resonance (Reference 2). La 0.67 Sr 0.33 From the spin current generating layer 102 made of MnO3, Sr x Ru y O 3-z A spin current is injected into the conversion layer 101, which is made of a material with a spin current of 0.01 Ω. The spin current is converted into a current in the conversion layer 101, which can be read as a voltage (Fig. 4). The symmetric component of the voltage that can be read is the contribution of the spin current-to-current conversion, so the symmetric component V sym and the asymmetric component V asym Decompose into:

[0026]

number

[0027] In equation (1), H is the external magnetic field, V(H) is the voltage dependent on the magnetic field, and H FMR =215.5 mT is the ferromagnetic resonance field.

[0028] ΔH is ΔH=√3 / 2ΔH ppFurthermore, by reversing the direction of the external magnetic field, the sign of the spin current changes, and the sign of the voltage obtained by conversion also changes (θH=180° in Figure 4). Measurements were taken at both angles of θH=0° and 180°, and the average V of the symmetrical component of each voltage was sym,ave =(V sym,0° -V sym,180° ) / 2, the change in the ferromagnetic resonance signal in the spin current generating layer 102 can be obtained by removing the contribution of the Seebeck effect and other factors. sym,ave Shows.

[0029] Next, we calculate the spin current. From the ferromagnetic resonance signal (Fig. 5), we obtain the full width at half maximum ΔH pp The damping constant can be calculated from the full width at half maximum using equation (2).

[0030]

number

[0031] In equation (2), γ and ω are the gyromagnetic ratio and the angular frequency of the microwave magnetic field (9.12 GHz), respectively.

[0032] Next, using equation (3), we calculate the spin mixing conductance g r ↑↓ Ask for.

[0033]

number

[0034] In equation (3), M s La 0.67 Sr 0.33 Saturation magnetization of MnO3 (50.6 emu / cm 3 ), d LSMO La 0.67 Sr 0.33 MnO3 film thickness, g is the g-factor, μ B is the Bohr magneton, α LSMO La 0.67 Sr 0.33is the damping constant of MnO3 alone. Here, g and α LSMO The values ​​are 1.95 and 1.57×10 -3 (See References 3 and 4.) The spin current density j s is calculated using equation (4).

[0035]

number

[0036] Spin Hall angle (θ SHE ) is estimated (obtained) using equation (5).

[0037]

number

[0038] In equation (5), λ is the spin diffusion length, l is the length between the first electrode 103 and the second electrode 104, and d SRO is the thickness of the conversion layer 101, σ LSMO is the spin current generating layer 102 (La 0.67 Sr 0.33 Conductivity of MnO3 (3.28×10 4 S / m), σ SRO is the conversion layer 101 (Sr x Ru y O 3-z ) conductivity (5.42×10 5 S / m), and e is the elementary charge. Here, the spin diffusion length is 1.5 nm, based on Non-Patent Document 7. The spin Hall conductivity σ SHE is σ SHE =θ SHE σ SRO It is expressed as:

[0039] Here, a part of Sr is replaced by an alkali atom or alkaline earth metal atom A (Sr 1-X A X ) x Ru y O 3-zEven if the conversion layer 101 is constructed from the above, if 0≦x≦0.05, 0.9≦x≦1.1, 0.9≦y≦1.1, and −0.1≦z≦0.1, the spin Hall angle (θ SHE ), spin Hall conductivity (σ SHE ) is 0.035, 1×10 4 A highly efficient spin-current-to-electric current conversion element exceeding {(h / 2π) / e}S / m (h is Planck's constant) can be obtained.

[0040] In addition, some of the Ru atoms were replaced with transition metal atoms (B) (Sr 1-X A X ) x (Ru 1-Y B Y ) y O 3-z Even if the conversion layer 101 is constructed from the above, if 0≦X≦0.05, 0≦Y≦0.05, 0.9≦x≦1.1, 0.9≦y≦1.1, and −0.1≦z≦0.1, the spin Hall angle (θ SHE ), spin Hall conductivity (σ SHE ) is 0.035, 1×10 4 A highly efficient spin-current to electric current conversion element exceeding {(h / 2π) / e} can be obtained.

[0041] A stacked structure of a conversion layer 101 (12 nm thick) and a spin current generation layer 102 (10 nm thick) fabricated on a substrate 111 was processed using a dicing machine to form the spin element described with reference to Figure 3. Indium (In) electrodes were used as the first electrode 103 and the second electrode 104. The first electrode 103 and the second electrode 104 can be made of a conductive material such as Ag, Au, Cr, or Nb-doped SrTiO3.

[0042] Here, the conversion layer is Sr x Ru y O 3-z If the composition of each element in SrRuO3 deviates from the stoichiometric composition by more than 10%, it is not possible to obtain a high spin-current-electric current conversion efficiency. For example, in SrRuO3, the composition of Ru deviates from the stoichiometric composition by 30%. 0.7 When a conversion layer is formed from O3 to form a spin element similar to the above, θSHE , σ SHE are 0.0052 and 1.6×10 3 {(h / 2π) / e}S / m.

[0043] Next, another spin element according to an embodiment will be described with reference to FIG. 6. This spin element includes a magnetic tunnel junction element 120 formed on a spin current generation layer 102. The magnetic tunnel junction element 120 includes an insulating layer (tunnel insulating layer) 105 formed on the spin current generation layer 102, and a second magnetic layer 106 made of a ferromagnetic material formed on the insulating layer 105. In this example, the spin current generation layer 102 is commonly used as one of the first magnetic layers of the magnetic tunnel junction element 120. The insulating layer 105 can be made of, for example, SrTiO3. The second magnetic layer 106 can be made of, for example, La 0.67 Sr 0.33 It can be composed of MnO3.

[0044] As described above, a memory element can be formed by combining with the magnetic tunnel junction element 120. x Ru y O 3-z Highly efficient spin-current-to-electric current conversion elements using this material will enable the realization of novel memory elements.

[0045] As described above, SrTiO3 is grown on the spin current generating layer 102 by a growth method such as molecular beam epitaxy to form the insulating layer 105, and then La 0.67 Sr 0.33 MnO3 is grown to form the second magnetic layer 106. 0.67 Sr 0.33 The spin current generating layer 102 (first magnetic layer) is made of MnO3, the insulating layer 105 is made of SrTiO3, and the 0.67 Sr 0.33 The laminated structure with the second magnetic layer 106 made of MnO3 acts as a magnetic tunnel junction element 120 that exhibits the tunnel magnetoresistance effect.

[0046] By passing a current through the conversion layer 101, a spin current is injected into the spin current generation layer 102 (first magnetic layer) by spin current-to-current conversion, and the memory is rewritten by controlling the magnetization direction of the spin current generation layer 102. The magnetization direction of the spin current generation layer 102 can be detected by the resistance state of the magnetic tunnel junction element 120.

[0047] As described above, according to the embodiment of the present invention, the conversion layer having the inverse spin-Hall effect is formed by using (Sr 1-X A X ) x (Ru 1-Y B Y ) y O 3-z (0≦X≦0.05, 0≦Y≦0.05, 0.9≦x≦1.1, 0.9≦y≦1.1, -0.1≦z≦0.1, A is an alkaline earth metal, B is a transition metal), which makes it possible to realize a more efficient spin-current-to-electric current conversion element using a ferromagnetic material containing Sr, Ru, and O.

[0048] It should be noted that the present invention is not limited to the embodiments described above, and it is clear that many modifications and combinations can be made by a person having ordinary knowledge in the art within the technical concept of the present invention. [Reference 1] H. Emoto, Y. Ando, ​​E. Shikoh, Y. Fuseya, T. Shinjo and M. Shiraishi, "Conversion of pure spin current to charge current in amorphous bismuth", Journal of Applied Physics 115, 17C507 (2014). [Reference 2] K. Ando and E. Saitoh, "Inverse spin-Hall effect in palladium at room temperature," Journal of Applied Physics 108, 113925 (2010). [Reference 3] HK Lee, I. Barsukov, AG Swartz, B. Kim, L. Yang, HY Hwang and IN Krivorotov, "Magnetic anisotropy, damping, and interfacial spin transport in Pt / LSMO bilayers", AIP Advances 6, 055212 (2016). [Reference 4] GY Luo, M. Belmeguenai, Y. Roussigne, CR Chang, JG Lin and SM Cherif, "Enhanced magnetic damping in La0.7Sr0.3MnO3 capped by normal metal layer", AIP Advances 5, 097148 (2015). [Explanation of symbols]

[0049] 101...replacement layer, 102...surge generation layer, 103...first electrode, 104...second electrode, 105...insulating layer, 106...second magnetic layer, 111...substrate, 120...magnetic PTFE junction element.

Claims

1. (Sr 1-X A X ) x (Ru 1-Y B Y ) y O 3-z a conversion layer having an inverse spin Hall effect and made of a ferromagnetic material with a perovskite structure (0≦X≦0.05, 0≦Y≦0.05, 0.9≦x≦1.1, 0.9≦y≦1.1, −0.1≦z≦0.1, A is an alkaline earth metal, B is a transition metal); and a spin current generation layer made of a ferromagnetic material and formed on the conversion layer. A spin element comprising:

2. 2. The spin element according to claim 1, The conversion layer is made of SrRuO, the deviation of which from the stoichiometric composition is within 10%. 3 A spin element composed of:

3. 3. The spin element according to claim 1, A spin element comprising a magnetic tunnel junction element formed on the spin current generation layer.

4. 4. The spin element according to claim 3, The magnetic tunnel junction element comprises: a first magnetic layer made of a ferromagnetic material; an insulating layer formed on the first magnetic layer; a second magnetic layer made of a ferromagnetic material and formed on the insulating layer; A spin element comprising:

5. 5. The spin element according to claim 4, The first magnetic layer is a layer commonly used as the spin current generation layer.

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