Control of magnetic anisotropy in Fe_1-xCo_x films on vicinal GaAs and Sc_1-yEr_yAs surfaces

We demonstrate that two distinct surface contributions to the magnetocrystalline anisotropy can be used to control the magnetic properties of thin films of bcc Fe_1-xCo_x grown on GaAs (100) and Sc_1-yEr_yAs (100). The bare GaAs (100) surface has twofold symmetry, and Fe_1-xCo_x films grown directly on it show a strong uniaxial magnetic anisotropy. Fourfold symmetry is restored in films grown on interlayers of Sc_1-yEr_yAs, in which the rock-salt structure provides a fourfold symmetric surface. A uniaxial magnetic anisotropy can be induced in this case by miscutting the substrate towards a {111} plane, so that vicinal steps run along a 〈011〉 direction. A simple Néel pair-bonding model describes the evolution of the anisotropy with the degree of miscut. For miscut GaAs (100) surfaces without interlayers, both the intrinsic anisotropy originating from the surface bonding and a step-induced term contribute to the total magnetic anisotropy. Depending on the orientation of the miscut, the step contribution can either enhance or partially suppress the intrinsic uniaxial anisotropy.