ホーム > 研究活動 > 口頭発表(2014) > Real space representation of magnetic anisotropy of metallic ferromagnets with non-periodic lattice structure

研究活動

Real space representation of magnetic anisotropy of metallic ferromagnets with non-periodic lattice structure

59th Annual Magnetism & Magnetic Materials Conference

2014.11.3-7
(2014.10.20 更新)

J. Inoue(University of Tsukuba, Tohoku University)

Abstract

 The magnetic anisotropy (MA) is strongly related to lowering of the crystal symmetry. In practical permanent magnets, further lowering of the crystal symmetry or even disappearance of the crystal symmetry occurs at grain boundaries. The perpendicular MA of thin films is often originated from the lowering of the crystal symmetry at interfaces. Disordered configuration of atoms may also be inevitable near the interface. To clarify effects of such non-periodicity on MA, we develop a microscopic theory for MA of ferro- magnetic materials with non-periodic lattice structures. Using the full orbital tight-binding model, we expand the thermodynamic potential in terms of the spin-orbit interaction (SOI) and Green’s functions. The Green’s functions are calculated by using symmetry conserving recursive method [1]. As our first study, we express the uniaxial MA in terms of the intra- and inter-sites Green’s functions and SOI. Because the inter-site Green’s functions are related to non-local susceptibilities and the SOI gives rise to inter-orbital transitions, the uniaxial MA constant shows oscillatory dependence on the inter-site distance and on the poison of Fermi energy [2]. The oscillatory feature may result in a complicated material dependence of the uniaxial MA constant. We have performed numerical calculation of the uniaxial MA constants of bulk L10 FePt and L10 FePt films in contact with fcc metals. The value of the uniaxial MA constant of the bulk FePt agrees semiquantitatively with that calculated in the first principles method [3]. It is also shown that a uniaxial MA is induced within several layers of fcc metals in contact with FePt layers. Numerical results of the uniaxial MA for Y-Fe intermetallic compounds with complex lattice structures will also be reported. This work was supported by ESICMM project of MEXT, Japan. The author thanks Profs. H. Tsuchiura and S. Ishio for useful discussions.[1] J. Inoue and Y. Ohta, J. Phys. C: Solid State Phys. 20, 1947 (1987), and refs. therein. [2] V. Heine and J. H. Samson, J. Phys. F: Metal Phys. 10, 2609 (1980). [3] A. Sakuma, J. Phys. Soc. Jpn. 63, 3053 (1994).



研究活動

元素戦略拠点

触媒・電池元素戦略拠点
触媒・電池元素戦略研究拠点 (京都大学)
東工大元素戦略拠点
東工大元素戦略拠点 (東京工業大学)
構造材料元素戦略研究拠点
構造材料元素戦略研究拠点 (京都大学)
高効率モーター用磁性材料技術研究組合
高効率モーター用 磁性材料技術研究組合