Atomic scale evolution of magnetic anisotropies

The results of in situ studies of the evolution of the magnetic anisotropy of Co(100) and Co(110) epitaxial films are discussed. It is shown that uniaxial magnetic anisotropies are the generic signature of symmetry breaking atomic and nm scale structures, e.g. steps, clusters, islands revealed by scanning tunnelling microscopy (STM) studies, and are strongly affected by nonmagnetic overlayers. However, the thickness dependent behaviour is surprisingly complex, with strong changes in anisotropy behaviour occurring with submonolayer depositions of nonmagnetic overlayers, These effects cannot be understood within the usual framework of the Neel model but are discussed in terms of several contributing mechanisms, e.g. strain, dipolar interactions and edge and surface anisotropies.