Theoretical Study on Crystalline Magnetic Anisotropy and Gilbert Damping in Finite Temperature

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K14800
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Physical properties of metals/Metal-base materials
• Research Institution: Tohoku University
• Principal Investigator: MIURA Daisuke 東北大学, 工学研究科, 助教 (90708455)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 結晶磁気異方性 / ギルバート緩和 / 微視的理論

Outline of Final Research Achievements

We have investigated the temperature dependencies of the crystalline anisotropy and the magnetic damping in ferromagnets, which are, respectively, characterized by a crystalline anisotropy constant, Ku(T), and a Gilbert damping constant, α(t), at a finite temperature T. Our purpose is to reveal the origin of the temperature dependencies in the same footing and from microscopic viewpoints.
In this work, we derived an extension for the conventional Akulov-Zener-Callen-Callen law, and demonstrated that it well reproduces experimental Ku(T) for rare-earth magnets having complex temperature dependence. In addition, considering α(T) in the same rare-earth magnets, we suggested that rare-earth magnets have a considerable difference from understanding of the Kambersky theory.

Free Research Field

磁性物理

Academic Significance and Societal Importance of the Research Achievements

結晶磁気異方性は永久磁石の重要な性能指数である保磁力の支配因子であり，その温度特性を評価することは応用上極めて重要である．本研究では，Ku(T)を電子論に基づいて記述して実験結果を再現すると共に，その微視的起源を明らかにした．また，α(T)も同時に記述し，希土類永久磁石が示す温度特性は通常の遍歴磁性体が示すそれとは全く異なることを示唆する結果を得た．Ku(T)とα(T)は磁気デバイスの消費エネルギに深く関与しており，本研究で上記のような知見が得られたことは社会的意義が大きいと考える．