Epitaxial orientation and magnetic properties of MnAs thin films grown on (001) GaAs: Template effects

Abstract

We have studied template effects in molecular beam epitaxy (MBE) of ferromagnetic MnAs thin films on (001) GaAs substrates. When As₂ flux was first supplied without Mn flux on the (001) GaAs prior to the MnAs growth, the surface reconstruction was disordered c(4×4), a more As‐rich surface than c(4×4). The growth direction of the MnAs thin film grown on this surface is [1̄100] and the easy magnetization axis was found to be along the [1̄1̄20] of MnAs and the [110] of GaAs. In contrast, when one monolayer of Mn was first deposited on the c(4×4) GaAs surface and then As₂ flux was supplied to grow MnAs, the growth direction of the MnAs thin film was found to be mainly [1̄101], and the easy magnetization axis was along the [1̄1̄20] of MnAs and the [1̄10] of GaAs, 90° different with respect to the substrate. These results indicate the importance of the very first monolayer in controlling the epitaxial orientation and magnetic properties of epitaxial ferromagnetic MnAs thin films.