The temperature-dependent in- and out-of-plane magnetic anisotropies in superlattices

superlattices grown on MgO(001) are studied by ferromagnetic resonance (FMR). The temperature dependence of the second- and fourth-order in- and out-of-plane magnetic anisotropies were determined from azimuthal and polar angular-dependent FMR for an sample. A very small step-induced in-plane uniaxial anisotropy indicates the existence of very large atomically flat terraces resulting in a perfect structural quality, in agreement with x-ray diffraction studies. The competition between surface and volume anisotropic components results in an unusual temperature dependence of the total in-plane fourfold anisotropy possibly changing the easy axis from the [100] to [110] in-plane directions at temperatures higher than room temperature. Finally, the FMR-linewidth values are typical for samples with a very high degree of homogeneity, comparable to that of Fe whiskers.