Tunnelling, non-collinearity and current-induced switching in metal/heterojunctions

Abstract

Current-induced switching in heterojunctions such as Fe/Vac/Fe and Fe/Ge/Fe, including in the latter case homogeneous and inhomogeneous chemical disorder caused by holes (vacuum), is described theoretically in terms of a multi-scale approach based on ab initio calculations using the fully relativistic screened Korringa–Kohn–Rostoker method and the Landau–Lifshitz–Gilbert equation. It is found that (1) the presence of tunnelling can be a function of the relative angle between the orientations of the magnetization in the magnetic slabs; and (2) disorder is responsible for the occurrence of non-collinear magnetic ground states. Furthermore, it is found that the first terms in the expansion of the twisting energy in a power series in the cosine of this relative angle, namely the interlayer exchange energy term and the anisotropy term, can be used for a qualitative scheme not only to characterize the occurrence of non-collinear ground states, but also for the critical current needed to induce switching.