Magnetically stabilized surface alloys

We investigate the interrelation of magnetism and stability of ultrathin magnetic films and come to the conclusion that under certain circumstances there should exist magnetically stabilized two-dimensional surface alloys. We present ab initio results for the formation energy and the interdiffusion energy of Cu(001)c(2 × 2)3d surface alloy films. Results based on the density functional theory in the local spin density approximation (LSDA) indicate the existence of a thermodynamically stable surface alloy: Cu(001)c(2 × 2) Mn. Although in detail, the results depend on the Cu substrate, the trends presented below have an universal character. Therefore, Cu(100)c(2 × 2) Mn is only an example of a much wider class of magnetic surface alloys. Recently, several of these surface alloys have been found experimentally, showing an unexpectingly large structural corrugation of the surface alloy atoms. This will be discussed as a result of a large magneto-volume effect. We found in addition a non-magnetic surface alloy Ti/Cu(001), which is not yet confirmed experimentally. Total energy calculations were carried out using the full-potential linearized augmented planewave (FLAPW) method in film geometry.