Control of magnetic anisotropy by epitaxial strain in the n-type ferromagnetic semiconductor (In,Fe)Sb

We report the strain dependence of magnetic anisotropy in n-type ferromagnetic semiconductor (FMS) (In,Fe)Sb thin films grown on different buffer layers; ranging from an InSb buffer layer that induces in-plane tensile strain, to AlSb, GaSb, and InAs buffer layers that induce an increasing order of in-plane compressive strain. Using ferromagnetic resonance (FMR) measurements and theoretical fittings, we show that the magnetocrystalline anisotropy constant (Ki) changes its sign, corresponding to a change in its preference for an in-plane magnetization easy axis to a perpendicular magnetization easy axis, when the epitaxial strain is changed from tensile to compressive. Meanwhile, the shape anisotropy constant (Ksh), which favors an in-plane magnetization easy axis, has larger contribution over Ki. Thus, the effective magnetic anisotropy (Keff = Ki + Ksh) results in in-plane magnetic anisotropy in all our (In,Fe)Sb thin films. Our study presents the observation of FMR in the n-type FMS (In,Fe)Sb at different temperatures and under various strain conditions. We discuss the origin of the strain-dependent magnetization anisotropy of (In,Fe)Sb with the help of a band-structure model while taking p - d hybridization into account.