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横井 直人*; 齊藤 英治
Journal of Magnetism and Magnetic Materials, 545, p.168673_1 - 168673_12, 2022/03
被引用回数：0 パーセンタイル：0(Materials Science, Multidisciplinary)We propose a dual gravitational theory corresponding to isotropic ferromagnetic systems based on the holographic duality, and establish the holographic dictionary between physical quantities in ferromagnets and the gravitational theory. Utilizing the holographic dictionary, the holographic calculation in the dual gravitational theory is shown to reproduce thermodynamics of ferromagnets including ferromagnetic phase transitions and low-temperature behaviors originating from magnons and conduction electrons. We further derive the equation for magnetization dynamics in ferromagnets from the equations for scalar fields and non-abelian gauge fields on charged black holes in the dual gravitational theory. From these results, the holographic duality is expected to give a new guiding principle to explore new phenomena in spintronics and magnonics based on the gravitational perspective.
家田 淳一
no journal, ,
半導体技術の中核とも言える電界効果は、電界効果トランジスタの発明など大きな波及効果をもたらしている。ごく最近、磁気ダイナミクスを利用した新しいインダクタ原理が発見された。本講演では、電界による磁気ダイナミクスの制御を通じて電界による可変インダクタンスが実現できることを理論的に提案する。
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.
家田 淳一
no journal, ,
Emergent inductance appears universally when magnetization dynamics is coupled with conduction electrons based on a sequential action of spin torque and spinmotive force effects under ac currents. An original version of the emergent inductor using a spiral magnet can be extended to include the spin-orbit coupling effects. A striking common feature among emergent inductors is their size dependence of the effect; the inductance is inversely proportional to the sample cross-sectional area, opening a way for integrating an inductor element.
