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間宮 広明*; 大場 洋次郎; 寺田 典樹*; 廣井 孝介; 篠原 武尚
IEEE Transactions on Magnetics, 59(11), p.6500505_1 - 6500505_5, 2023/11
Neutron transmission spectroscopy is a promising characterization method. In addition, polarized neutrons provide further information via the detailed analysis of magnetic scattering contributions. In this study, we have investigated the contributions of ferrite, cementite, and retained austenite in an ultra-fine grained high carbon steel using the polarized neutron transmission spectroscopy. The polarized neutron transmission spectrum of the sample is well explained by the combination of ferrite and cementite and the amount of austenite can be ignored. This indicates that the polarized neutrons are helpful to evaluation of the complicated microstructures in carbon steels.
Lee, S.*; 仲田 光樹; Tchernyshyov, O.*; Kim, S. K.*
Proceedings of IEEE International Magnetics Conference 2023 (INTERMAG 2023) (Internet), 2 Pages, 2023/05
We theoretically investigate the interaction between magnons and a Skyrmion-textured domain wall in a two-dimensional antiferromagnet and elucidate the resultant properties of magnon transport by using supersymmetric quantum mechanics. Our results suggest that the thermal transport of an antiferromagnet is tunable by modulating the Skyrmion charge density of the domain wall, which might be useful for realizing electrically tunable spin caloritronic devices.
荒木 康史; 家田 淳一
no journal, ,
We theoretically propose novel functionalities of inductance and capacitance in heterostructures of topological insulators and magnets. Topological insulators show anomalous responses between electricity and magnetism, which are described not by the conventional Maxwell's equations, but by topological quantum field theory. Based on topological quantum field theory, we establish a unified theoretical framework applicable in arbitrary dimensions, to extract inductance and capacitance in topological insulators. We demonstrate the emergence of inductance and capacitance in several magnetic heterostructure setups, and show their advantages in achieving high operation frequency and high power efficiency.
森 道康; Ziman, T.*
no journal, ,
We introduce a simple model for the ferrimagnetic non-collinear "magnetic umbrella" states of rare-earth iron garnets (REIG), common when the rare-earth moments have non-zero orbital angular momentum. This could be used to determine the magnetic polarization of each mode and thereby the spin currents generated by thermal excitations including the effects of mixed chirality. By the symmetry of the model, only one rare earth mode hybridizes, inducing a gap at zero wave number and level repulsion at finite frequency. At the compensation point, the hybridization gap closes and finally, as we approach the N
el temperature, the hybridization gap appears to reopen. The chirality of the lowest mode changes its sign around the frequency at which the level repulsion occurs. This is important to estimate the spin current generation in REIGs.
鎌田 夏央輝*; 水上 成美*; 鈴木 和也
no journal, ,
垂直磁化した正方晶Mn基合金薄膜は、垂直磁気トンネル接合(p-MTJ)の強磁性電極として魅力的な材料である。本研究では、サファイア(r-plane)基板上に成長させたL10-MnGa超薄膜電極を用いて、p-MTJを実証することに成功した。基板とMnGa層の間にbcc-Ta/Cr/CoGaハイブリッドバッファ層を導入することで、サファイア(r-plane)基板上に単結晶のL10-MnGa極薄膜の成長に成功した。さらに、サファイア基板上に成長させたp-MTJは、室温で6-7%の明確なTMRを示した。これらの結果は、単結晶MnGa超薄膜の新しい成長技術が、単結晶MnGaを用いたスピントロニクスデバイスの開発につながることを示唆している。
家田 淳一
no journal, ,
Several embodiments of emergent inductance in ferromagnetic nanostructures are theoretically presented. The emergent inductance is a universal phenomenon when an order parameter such as magnetization in ferromagnets is coupled with conduction electron spin based on a sequential action of spin torque and spinmotive force effects under ac current application. An original version of the emergent inductor using a spiral magnet can be extended to include the spin-orbit coupling effects. Materials are not limited to metallic systems but also insulators. A striking common feature over the emergent inductors is their size dependence of the effect; the inductance is inversely proportional to the sample cross sectional area, opening a way for integration of an inductor element. We also discuss key performance factors: the operation frequency and quality factor that represents the energy efficiency of the inductive response.
