Grain Size Dependence of Exchange-Coupling Interaction between Magnetically Soft-Hard Grains and Effective Anisotropy
来源期刊：JOURNAL OF RARE EARTHS2004年第6期
论文作者：傅爽 韩广兵 冯维存 陈伟 刘汉强 高汝伟
Key words：metal materials; exchange-coupling interaction; effective anisotropy; magnetic grains; rare earths;
Abstract: Taking α-Fe and Nd2Fe14B grains as example, the grain size dependence of the exchange-coupling interaction and effective anisotropy and also their variations depending on the ratio of magnetically soft and hard grain sizes, Ds∶ Dh, were investigated. When grain size D>Lex, the grain's anisotropy is the statistic value of the coupled and uncoupled part. The anisotropy constant of uncoupled part is the common value K1 and that of coupled part varies with the distance to the grain surface. The effective anisotropy constant between magnetically soft and hard grains, Keff, can be expressed as the sum of the products of volume fractions for soft and hard grains, respectively, and the corresponding mean anisotropy constants. The calculation results indicate that the exchange-coupling interaction is enhanced with the reduction of grain size, and the effective anisotropy decreases with reducing grain size and increasing ratio of Ds∶ Dh. In order to get high effective anisotropy constant, Keff, in composite magnetically soft-hard grains, the hard grain size should be larger than 30 nm and the soft grain size should be about 10 nm.
傅爽1，韩广兵1，冯维存1，陈伟1，刘汉强1，高汝伟1
(1.School of Physics & Microelectronics, Shandong University, Jinan 250100, China)
Abstract:Taking α-Fe and Nd2Fe14B grains as example, the grain size dependence of the exchange-coupling interaction and effective anisotropy and also their variations depending on the ratio of magnetically soft and hard grain sizes, Ds∶ Dh, were investigated. When grain size D>Lex, the grain''s anisotropy is the statistic value of the coupled and uncoupled part. The anisotropy constant of uncoupled part is the common value K1 and that of coupled part varies with the distance to the grain surface. The effective anisotropy constant between magnetically soft and hard grains, Keff, can be expressed as the sum of the products of volume fractions for soft and hard grains, respectively, and the corresponding mean anisotropy constants. The calculation results indicate that the exchange-coupling interaction is enhanced with the reduction of grain size, and the effective anisotropy decreases with reducing grain size and increasing ratio of Ds∶ Dh. In order to get high effective anisotropy constant, Keff, in composite magnetically soft-hard grains, the hard grain size should be larger than 30 nm and the soft grain size should be about 10 nm.
Key words:metal materials; exchange-coupling interaction; effective anisotropy; magnetic grains; rare earths;
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