Magnetic anisotropy terms in [110] MBE grown REFe2 films involving the strain term ???

Abstract

The magnetic anisotropy parameters in [110] MBE grown films of REFe₂ compounds are not the same as those in the bulk. This is due to the presence of a shear strain ε_xy, frozen in during crystal growth. In this paper, calculated magnetic anisotropy parameters for [110] MBE grown REFe₂ films, that directly involve the shear strain ε_xy, are presented and discussed. In addition to the usual first order Callen and Callen term K˜'₂, there are nine second order terms six of which involve cross terms between ε_xy and the cubic crystal field terms B₄ and B₆. Two of the second order cross terms are identified as being important: K˜"₂₄₂(T) and K˜"₂₆₂(T). Of these, the rank-two term K˜"₂₄₂(T) dominates over a large temperature range. It has the same angular dependence as the first order term K˜'₂, but with a more rapid temperature dependence. The correction at T = 0K for TbFe₂, DyFe₂, HoFe₂, ErFe₂, and TmFe₂, amounts to ~+9.2%, -13.9%, -11.6%, +22.7%, and 27.1%, respectively. Similar comments are made concerning the rank-four K˜"₂₆₄(T) term.

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ORCID for H. Fangohr: orcid.org/0000-0001-5494-7193

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