Strain Induced Anisotropy Change in Ultrathin Fe Films Grown on MnAs(110)/GaAs(001)

Mechanical stress due to a misfit between a thin film and its substrate induces strains which can strongly modify the unstrained thin film properties. One good and interesting example to study strain effects is given by ultrathin films of Fe epitaxially grown on MnAs(110)/GaAs(001). The MnAs(110) films show, at room temperature, coexistence of two structural phases, which organize themselves forming a striped pattern. The Fe epilayer senses the strain effects due to lattice mismatch and to the border constraints given by the striped substrate. In this work, we are concerned with the consequences that this strain has on the magnetic anisotropy of the Fe thin film and try to explain recent experimental results. These experiments indicate an easy axis rotation of the film Fe atoms sitting on one of the striped phases. In order to have an approach to the understanding of the observed phenomenon, we make use of ab initio calculations and of the magnetoelastic model. We find that both the magnetoelastic model and the ab initio calculated spin orbit coupling point towards the strain effects as the most important contribution to the observed easy axis rotation.