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増田 啓人*; 山根 結太*; 土肥 昂尭*; 山崎 匠*; Modak, R.*; 内田 健一*; 家田 淳一; Kl
ui, M.*; 高梨 弘毅; 関 剛斎*
Advanced Science (Internet), 12(48), p.e14598_1 - e14598_9, 2025/12
被引用回数：0 パーセンタイル：0.00(Chemistry, Multidisciplinary)Current-induced domain-wall motion (CIDWM) in a synthetic antiferromagnet is a key phenomenon for developing potential high-density-packed magnetic domain-wall memory with fast operation. Here, we report CIDWM in the antiferromagnetically-coupled two Co layers through the Ir interlayer sandwiched by the two Pt layers: Pt/Co/Ir/Co/Pt. The top and bottom Pt layers play a role for generating the spin current coming from the spin Hall effect, which gives rise to the dual spin-orbit torque (SOT) acting on the perpendicular magnetizations of the Co layers. Although a simple argument would predict that SOTs from top and bottom Pt layers cancel each other out, the dual SOT nucleates a reversed magnetic domain and drives the CIDWM effectively at current density of the order of 10
A m
. This study also examines the effect of antisymmetric interlayer exchange coupling (AIEC) on CIDWM. We find a positive correlation between the magnitude of AIEC and the domain wall velocity whereas the current density required for nucleating the reversed domain shows a negative correlation with the magnitude of AIEC. These facts suggest that the existence of AIEC improves the performance of CIDWM. Our results provide a new avenue to design SOT domain wall devices based on a synthetic antiferromagnet.
山崎 匠*; 石谷 優剛*; 中田 勝之*; 佐々木 智生*; 遠藤 恭*; 高梨 弘毅; 関 剛斎*
Journal of Applied Physics, 138(23), p.233905_1 - 233905_11, 2025/12
The induction of large in-plane uniaxial magnetic anisotropy for the CoFeB-based thin films by post-annealing under the magnetic field application is reported. The comprehensive study reveals the influence of CoFeB composition and Pt addition to CoFeB on the induced magnetic anisotropy by magnetic field annealing. The addition of Pt to a CoFeB film significantly enhances the effect of magnetic field annealing, and as a result, the CoFeB-Pt films exhibit the in-plane uniaxial magnetic anisotropy energies that are one order of magnitude larger than the pristine CoFeB films. In order to understand the mechanism of magnetic anisotropy induction by post-annealing, the magnetostriction measurement for the CoFeB-based thin films were carried out. The correlation between the induced magnetic anisotropy and magnetoelastic properties is discussed.
鈴木 和也; 窪田 崇秀*; 高梨 弘毅
APL Materials (Internet), 13(10), p.101108_1 - 101108_6, 2025/10
被引用回数：0 パーセンタイル：0.00(Nanoscience & Nanotechnology)磁性FeCoNiCuPdハイエントロピー合金(HEA)薄膜の構造、磁気、および磁気伝達特性を調査し、重元素であるパラジウム(Pd)が磁気伝達において果たす役割を評価した。銅とパラジウムの組成比を変えたFeCoNiCuPd薄膜は、室温でコスプッタリング法により作製され、単相fcc構造を示した。作製されたすべての薄膜は、室温で軟磁性的なヒステリシスループを示しました。異方性磁気抵抗効果と異常ホール効果がPdに依存することは、大きなスピン軌道相互作用を持つ重金属が磁性HEAの磁気伝達において重要な役割を果たすことを示唆している。この発見は、将来のスピントロニクス材料のための磁性HEAにおける磁気伝達現象の理解を促進するだろう。
-ordered FePt thin films studied by angle-dependent X-ray magnetic circular dichroism芝田 悟朗; 池田 啓祐*; 高梨 弘毅; 藤森 淳*; 他8名*
Applied Physics Letters, 127(14), p.142406_1 - 142406_6, 2025/10
被引用回数：0 パーセンタイル：0.00(Physics, Applied)We have investigated the contribution of the Fe 
electrons to its magnetic anisotropy energy by angle-dependent X-ray magnetic circular dichroism at the Fe 
edge. By this technique, one can deduce the magnetic dipole moment 
, which represents the anisotropic spatial distribution of spin-polarized electrons, and the orbital moment anisotropy (OMA) of Fe electrons. Detected finite indicates that the spin-polarized Fe electrons are distributed preferentially in the out-of-plane direction of the films. This of Fe overwhelms the positive contribution of OMA to PMA, and reduces the PMA of -ordered FePt thin films, consistent with a previous first-principles calculation. The present result implies that a large positive contribution of the non-magnetic element Pt rather than Fe governs the PMA of -ordered FePt thin films.
Mn
N and Fe
Co
N filmsYin, W.*; 伊藤 啓太*; 坪和 優佑*; 辻川 雅人*; 白井 正文*; 梅津 理恵*; 高梨 弘毅
Journal of Magnetism and Magnetic Materials, 628, p.173157_1 - 173157_8, 2025/09
被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)Fe
N exhibits a large anomalous Nernst effect (ANE), which motivates a systematic study of enhancing the anomalous Nernst coefficient (S
) by modulating its electronic and magnetic structures. In this study, Mn and Co substitution effects for Fe in FeN on S
were investigated. FeMnN and FeCoN films in wide ranges of x and y were grown epitaxially on MgO(001) and (LaAlO
)
(Sr
TaAlO
)
(001) substrates, respectively, using molecular beam epitaxy. The S value of the FeN film is suppressed by substituting Fe with Mn or Co. By measuring the ANE, Seebeck effect, and anomalous Hall effect, the transverse thermoelectric conductivity (
) was evaluated. The composition dependence of S was dominated by the change of for both FeMnN and FeCoN films. First-principles calculations were conducted for the transverse electric conductivity (
) and of FeN and Fe
Co
N, and large leading to large S was predicted in FeCoN.
窪田 崇秀*; 鈴木 和也; Hirayama, Yoshiyuki*; Takahashi, Shigeki*; 高梨 弘毅
Physical Review Materials (Internet), 9(8), p.084408_1 - 084408_7, 2025/08
被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)High-entropy alloys (HEAs) exhibit various physical properties, such as high microhardness for structured materials and high efficiency for catalysis. These features are recognized as a cocktail effect of five or more elements that stabilize a single-phase solid solution due to a high configurational entropy.
Ding, H.*; 伊藤 啓太*; 遠藤 恭*; 高梨 弘毅; 関 剛斎*
Journal of Physics D; Applied Physics, 57(38), p.385002_1 - 385002_10, 2024/09
被引用回数：4 パーセンタイル：53.37(Physics, Applied)This paper reports the systematic study on the structure, magnetic properties and magnetoelastic properties for the Fe
Ga (001) thin films epitaxially grown on the different substrates of GaAs(001) and MgO(001) using the sputtering technique. The alloy composition dependence of effective magnetoelastic coupling coefficient B
along the FeGa [110] direction indicated that the largest magnetoelastic coupling was obtained for the Fe-Ga layer with x = 30 grown on the MgO substrate. Considering the results of structural analysis and magnetization measurement, the different crystallite sizes depending on the kind of substrate may give rise to the different magnetoelastic coupling strengths between the Fe-Ga layers on the MgO and the GaAs. The magnetostriction along the FeGa [111] direction was also estimated with the assumption of plausible elastic property of Fe-Ga, and showed the values comparable to the reported value of bulk Fe-Ga. This means the large magnetostriction can be obtained even for the Fe-Ga thin films epitaxially grown not only on the GaAs(001) but also on the MgO(001). The findings in this work will give a guideline for designing spintronic applications with a Fe-Ga layer exhibiting a large magnetoelastic coupling.
高梨 弘毅; 関 剛斎*
まぐね, 19(3), p.100 - 106, 2024/06
薄膜の垂直磁気異方性は、磁気記録のみならずスピントロニクスにおいても重要な役割を果たしている。本解説記事では、垂直磁気異方性に関して、磁気多層膜、規則合金膜、希土類遷移金属アモルファス合金多層膜、不均一膜やグラニュラー膜など、垂直磁化を持つ具体例を示しながら、基礎からこれまでの研究、そして最近の研究動向を概説する。それぞれの具体例について、構造対称性の破れによる界面磁気異方性、ひずみによる磁気弾性異方性、バルクの結晶磁気異方性、原子の方向性規則配列などの垂直磁気異方性の物理的起源を議論する。
関 剛斎*; 内田 健一*; 高梨 弘毅
Journal of Physics; Condensed Matter, 36(33), p.333001_1 - 333001_11, 2024/05
被引用回数：2 パーセンタイル：5.15(Physics, Condensed Matter)Spin caloritronics, a research field studying on the interconversion between a charge current (J
) and a heat current (J
) mediated by a spin current (J
) and/or magnetization (M), has attracted much attention not only for academic interest but also for practical applications. Newly discovered spin-caloritronic phenomena such as the spin Seebeck effect (SSE) have stimulated the renewed interest in the thermoelectric phenomena of a magnet, which have been known for a long time, e.g. the anomalous Nernst effect (ANE). These spin-caloritronic phenomena involving the SSE and the ANE have provided with a new direction for thermoelectric conversion exploiting J and/or M. Importantly, the symmetry of ANE allows the thermoelectric conversion in the transverse configuration between J and J. Although the transverse configuration is totally different from the conventional longitudinal configuration based on the Seebeck effect and has many advantages, we are still facing several issues that need to be solved before developing practical applications. The primal issue is the improvement of conversion efficiency. In the case of ANE-based applications, a material with a large anomalous Nernst coefficient (S) is the key for solving the issue. This review article introduces the increase of S can be achieved by forming superlattice structures, which has been demonstrated for several kinds of materials combinations. The overall picture of studies on spin caloritronics is first surveyed. Then, we mention the pioneering work on the transverse thermoelectric conversion in superlattice structures, which was performed using Fe-based metallic superlattices, and show the recent studies for the Ni-based metallic superlattices and the ordered alloy-based metallic superlattices.
-FeNi films with island structures on LaAlO(110) substrates by nitrogen insertion and topotactic extraction西尾 隆宏*; 伊藤 啓太*; 藏 裕彰*; 高梨 弘毅; 柳原 英人*
Journal of Alloys and Compounds, 976, p.172992_1 - 172992_8, 2024/03
被引用回数：3 パーセンタイル：40.95(Chemistry, Physical)Tetrataenite (L1-FeNi) has potential for application in next-generation permanent magnets. This compound is a rare-earth-free material comprising Fe and Ni, which are abundant elements. In addition, an extremely high uniaxial magnetocrystalline anisotropy (
u) is expected for L1-FeNi because of the ordered arrangement of the elements. This study reports the magnetic properties of uniaxially oriented L1-FeNi films with island structures fabricated by a novel method involving the radio-frequency sputter deposition of FeNi alloy films onto a LaAlO(110) substrate, followed by nitrogen insertion and topotactic extraction. FeNiN(110) films are epitaxially grown on the LAO(110) plane by the nitriding and additional annealing process of the FeNi alloy films at high temperatures under ammonia gas to reduce the volume fraction of crystallographic variants. Uniaxially oriented L1-FeNi alloy films with island structures are obtained after the topotactic denitriding of the FeNiN films. The uniaxial magnetic anisotropy of the L1-FeNi films is determined from the magnetization curves and via magnetic torque measurements of the films. The obtained L1-FeNi film exhibiting a relatively high superlattice order parameter of 0.74 yielded a uniaxial magnetocrystalline anisotropy energy of ~0.63 MJ/m
at 300 K, as well as coercivities of 319 and 358 kA/m at 300 and 10 K, respectively. This coercivity is the highest value reported for artificial L1-FeNi to date.
山崎 匠*; 平井 孝昌*; 八木 貴志*; 山下 雄一郎*; 内田 健一*; 関 剛斎*; 高梨 弘毅
Physical Review Applied (Internet), 21(2), p.024039_1 - 024039_11, 2024/02
被引用回数：5 パーセンタイル：61.50(Physics, Applied)This study presents a measurement method for determining the figure of merit for transverse thermoelectric conversion in thin-film forms. Leveraging the proposed methodology, we comprehensively investigate the transverse thermoelectric coefficient, in-plane electrical conductivity, and out-of-plane thermal conductivity in epitaxial and polycrystalline Fe/Pt metallic multilayers.
Fe
Mn
Si heusler alloy thin filmsNabialek, A.*; Chumak, O.*; 関 剛斎*; 高梨 弘毅; Baczewski, L. T.*; Szymczak, H.*
IEEE Transactions on Magnetics, 59(11), p.2501405_1 - 2501405_5, 2023/11
被引用回数：2 パーセンタイル：18.57(Engineering, Electrical & Electronic)The anisotropic magnetoelastic (ME) properties of epitaxial CoFeMnSi(CFMS) Heusler alloy thin films with thicknesses ranging from 8 to 100 nm were investigated using the strain-modulated ferromagnetic resonance (SMFMR) technique. The calculation of the first cubic magnetocrystalline (MC) constant 
and the two cubic ME constants 
and was carried out assuming the cubic symmetry of the magnetic layer. A significant negative perpendicular MC anisotropy, of the order of 10
J/m, was also observed. The investigated parameters were found to be dependent on the thickness of the magnetic layer. The thinnest magnetic layers showed the strongest cubic MC anisotropy and the weakest anisotropy of ME properties. These findings highlight the importance of considering the magnetic layer thickness when evaluating the anisotropy in the ME properties of Heusler alloy thin films.
廣畑 貴文*; Lloyd, D. C.*; 窪田 崇秀*; 関 剛斎*; 高梨 弘毅; 介川 裕章*; Wen, Z.*; 三谷 誠司*; 小泉 洸生*
IEEE Access, 11, p.117443 - 117459, 2023/10
被引用回数：6 パーセンタイル：24.27(Computer Science, Information Systems)Spintronic devices are expected to replace the recent nanoelectronic memories and sensors due to their efficiency in energy consumption and functionality with scalability. To date, spintronic devices, namely magnetoresistive junctions, employ ferromagnetic materials by storing information bits as their magnetization directions. However, in order to achieve further miniaturization with maintaining and/or improving their efficiency and functionality, new materials development is required: 1) increase in spin polarization of a ferromagnet or 2) replacement of a ferromagnet by an antiferromagnet. Antiferromagnetic materials have been used to induce an exchange bias to the neighboring ferromagnet but they have recently been found to demonstrate a 100% spin-polarized electrical current, up to THz oscillation and topological effects. In this review, the recent development of three types of antiferromagnets is summarized with offering their future perspectives towards device applications.
FeMnSi Heusler alloysNabialek, A.*; Chumak, O. M.*; Aleshkevych, P.*; Domagala, J. Z.*; Pacewicz, A.*; Salski, B.*; Krupka, J.*; 関 剛斎*; 高梨 弘毅; Baczewski, L. T.*; et al.
Scientific Reports (Internet), 13, p.17016_1 - 17016_9, 2023/10
被引用回数：8 パーセンタイル：55.34(Multidisciplinary Sciences)The perpendicular magnetocrystalline anisotropy, magnetoelastic properties as well as the Gilbert damping factor in CoFeMnSi thin films were found to depend on a magnetic layer thickness, and they can be also tuned by the application of additional Ag buffer layer. The tetragonal distortion of a magnetic layer was found to increase with decreasing thickness, and after the application of an additional Ag buffer layer, the character of this distortion was changed from tensile to compressive in the plane of a film. A correlation between the tetragonal distortion and perpendicular magnetocrystalline anisotropy was found. However, the magnitude of the observed tetragonal distortion for most samples seems to be too small to explain alone the experimentally found large magnitude of the perpendicular magnetocrystalline anisotropy. For these samples, other mechanisms including both surface and volume effects must be taken into account.
山崎 匠*; 関 剛斎*; 窪田 崇秀*; 高梨 弘毅
Applied Physics Express, 16(8), p.083003_1 - 083003_4, 2023/08
被引用回数：3 パーセンタイル：26.28(Physics, Applied)We report the effect of the epitaxial growth of NiO films on its spin current transmission. Two sample series of Pt/NiO/CoFeB, including epitaxial and polycrystalline NiO, were prepared using different deposition conditions. The spin current transmission of NiO is evaluated using the thermo-spin effects in the trilayers. Epitaxial NiO exhibits a non-monotonic behavior in the NiO thickness dependence of spin current transmission, while this behavior is smeared out in polycrystalline NiO. The non-monotonic behavior implies the presence of multiple spin transport mechanisms, which becomes apparent with epitaxial growth.
SnS-based shandite filmsLau, Y.-C.*; 池田 絢哉*; 藤原 宏平*; 小沢 耀弘*; Zheng, J.*; 関 剛斎*; 野村 健太郎*; Du, L.*; Wu, Q.*; 塚崎 敦*; et al.
Physical Review B, 108(6), p.064429_1 - 064429_11, 2023/08
被引用回数：14 パーセンタイル：78.13(Materials Science, Multidisciplinary)Magnetic Weyl semimetals (mWSMs) are characterized by linearly dispersive bands with chiral Weyl node pairs associated with broken time-reversal symmetry. One of the hallmarks of mWSMs is the emergence of large intrinsic anomalous Hall effect. On heating the mWSM above its Curie temperature, the magnetism vanishes while exchange-split Weyl point pairs collapse into doubly degenerate gapped Dirac states. Here, we reveal the attractive potential of these Dirac nodes in paramagnetic state for efficient spin current generation at room temperature via the spin Hall effect. Ni and In are introduced to separately substitute Co and Sn in a prototypal mWSM CoSnS shandite film and tune the Fermi level. Composition dependence of spin Hall conductivity for paramagnetic shandite at room temperature resembles that of anomalous Hall conductivity for ferromagnetic shandite at low temperature; exhibiting peak-like dependence centering around the Ni-substituted CoNiSnS and undoped CoSnS compositions, respectively. The observed spin Hall and anomalous Hall conductivity maxima at different compositions reflect optimum Fermi-level positioning relative to the paramagnetic Dirac and magnetic Weyl states, suggesting the common origin and intercorrelation between the two Hall effects. Our findings highlight a strategy for the quest of spin Hall materials, guided by the abundant experimental anomalous Hall-effect data of ferromagnets in the literature.
高梨 弘毅
まてりあ, 62(5), p.301 - 306, 2023/05
金属人工格子とは、異種金属をナノメートルスケールで積層した人工物質である。金属人工格子の研究は、巨大磁気抵抗効果や層間交換結合の観点で、1980年代後半から1990年代前半にかけて、多くの研究がなされた。さらに、金属人工格子の研究はスピントロニクスという新たな分野を生み、21世紀に入りスピントロニクスは大きく成長した。そしてスピントロニクスの発展の中で、今また金属人工格子の新たな有用性が注目されている。本稿では、筆者のこれまでの成果を示しつつ、金属人工格子の研究の流れと最近のトピックスをまとめる。なお、本稿は2023年3月の日本金属学会春期大会での本多記念講演に基づき、原稿化されたものである。
増田 啓人*; 山根 結太*; 関 剛斎*; Raab, K.*; 土肥 昂尭*; Modak, R.*; 内田 健一*; 家田 淳一; Klui, M.*; 高梨 弘毅
Applied Physics Letters, 122(16), p.162402_1 - 162402_7, 2023/04
被引用回数：4 パーセンタイル：34.93(Physics, Applied)We report current-induced magnetization switching in Pt/Co/Ir/Co/Pt multilayers with different Ir layer thicknesses (
), where the perpendicularly magnetized Co layers are coupled ferromagnetically or antiferromagnetically through an interlayer exchange coupling and are sandwiched by the Pt spin Hall layers. The domain structures formed during switching vary depending on the magnetization alignment, i.e., ferromagnetically coupled or antiferromagnetically coupled configuration. These results clarify the macroscopic picture of switching process for interlayer exchange-coupled systems. The local picture of the switching process is also examined by a numerical calculation based on a macrospin model, which reveals the switching dynamics triggered by dual spin-orbit torque for both antiferromagnetically and ferromagnetically coupled cases. The numerical calculation shows that the dual spin-orbit torque from the two Pt layers effectively acts on the two Co layers not only for the antiferromagnetically coupled case but also for the ferromagnetically coupled one. Our findings deepen the under- standing of the switching mechanism in a magnetic multilayer and provide an avenue to design spintronic devices with more efficient spin-orbit torque switching.
Zhou, Z.*; Frost, W.*; Lloyd, D. C.*; 関 剛斎*; 窪田 崇秀*; Ramos, R.*; 齊藤 英治; 高梨 弘毅; 廣畑 貴文*
Journal of Magnetism and Magnetic Materials, 571, p.170575_1 - 170575_5, 2023/04
被引用回数：1 パーセンタイル：6.48(Materials Science, Multidisciplinary)Recent development in neuromorphic computation allows us to achieve low power and highly efficient calculations better than the conventional von Neumann computation. In order to achieve realistic synaptic operation, potentiation to add weighting to strengthen a selected artificial synapse. Such functionality can be achieved by reducing the electrical resistance of the artificial synapse. Recently, a ferromagnetic Heusler alloy used in a magnetoresistive junction has been demonstrated to crystallise via the layer-by-layer mode by introducing an electrical current pulse. In this study, we have extended the current-induced crystallisation to a junction with epitaxially-grown Heusler alloy after post-annealing for crystallisation. By combining this potentiation functionality with the neuromorphic operation, realistic synaptic computation can be developed.
MnSi重田 出*; Oku, Shuta*; 窪田 崇秀*; 木村 尚次郎*; 関 剛斎*; 篠崎 文重*; 淡路 智*; 高梨 弘毅; 廣井 政彦*
AIP Advances (Internet), 13(2), p.025116_1 - 025116_5, 2023/02
被引用回数：1 パーセンタイル：7.50(Nanoscience & Nanotechnology)Superconducting properties were investigated in epitaxially layered films consisting of superconductor NbN and half-metallic Heusler alloy CoMnSi(CMS). Temperature dependence of the electrical resistivity 
(T) was measured by applying perpendiar magnetic fields to the surface of NbN/CMS films. With the increase of the CMS thickness 
, the upper critical field 
H
decreased monotonically, but the superconducting transition temperature T
had the minimum of 10.1 K at 
5 nm. The T behavior was in qualitative agreement with the theory of the 
-coupling. The pair-breaking parameter 
determined by the superconducting fluctuation theory took the maximum at = 3
5 nm, which would be related to the minimum of 
. The experimental results reveal that the superconductivity of the NbN layer in NbN/CMS films is affected by the interplay between the superconducting NbN layer and the half-metallic CMS layer.
