In-plane magnetic anisotropies in Fe films on vicinal Ag(001) and Au(001) surfaces

In-plane fourfold and uniaxial magnetic anisotropies were studied in Fe fil ms epitaxially grown on vicinal Ag(001) and Au(001) surfaces, which were pr epared by molecular beam epitaxy on miscut GaAs(001) substrates. The effect ive fourfold and uniaxial anisotropy constants, K-1(eff) and K-u(eff), whic h are determined from magnetisation curves measured with the magneto-optic Kerr effect, are linear functions of the inverse Fe layer thickness. The fo urfold anisotropy shows a rotation of the easy and hard axes by 45 degrees below a critical thickness of 6-7 ML. The uniaxial term is mainly an interf ace contribution. We find that the orientation of the uniaxial easy axis de pends on the Fe thickness. In thinner films (t(Fe) less than or equal to 20 ML) it is oriented perpendicular to the step edges, i.e., parallel to Fe[1 00]. This excludes shape anisotropy as the main mechanism. Above a critical thickness the uniaxial easy axis is aligned parallel to the step edges, i. e., along Fe[010]. This step-induced uniaxial anisotropy may be due to modi fied electronic states and to strain from the large vertical misfit at the steps. (C) 1999 American Institute of Physics. [S0021-8979(99)64408-5].