Magnetic anisotropy terms in [110] MBE-grown REFe(2) films involving the strain term ε(xy)

The magnetic anisotropy parameters in [110] MBE-grown films of REFe(2) (RE, rare earth) 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, magnetic anisotropy parameters for [110] MBE-grown REFe(2) films, that directly involve the shear strain ε(xy), are presented and discussed. In addition to the usual first-order Callen and Callen term [Formula: see text], there are nine second-order terms, six of which involve cross-terms between ε(xy) and the cubic crystal field terms B(4) and B(6). Two of the second-order cross-terms are identified as being important: [Formula: see text] and [Formula: see text]. Of these, the rank-two term [Formula: see text] dominates over a large temperature range. It has the same angular dependence as the first-order term [Formula: see text], but with a more rapid temperature dependence. The correction at T = 0 K for TbFe(2), DyFe(2), HoFe(2), ErFe(2) and TmFe(2), amounts to ∼+9.2%, -13.9%, -11.6%, +14.3%, and 27.1%, respectively. Similar comments are made concerning the rank-four [Formula: see text] term.