Magnetism of Co clusters embedded in Cu(0 0 1) surfaces: an ab initio study

We report calculations of electronic structure and magnetic properties of Co clusters (up to 50 atoms) embedded in Cu(0 0 1) surfaces, performed using the first-principles linear muffin tin orbital-atomic sphere approximation method, implemented directly in real space. Co agglomerates of different sizes and shapes are considered in order to investigate the influence of the local environment around the Co sites to the magnetism in this class of systems. We find that the magnitude of the Co moments is mainly governed by two factors: the position of the site relative to the Cu(0 0 1) surface layer and the number of Cu neighbors. The results show moment enhancement for sites located above the surface and/or placed substitutionally in the surface layer, due to their reduced coordination numbers. For sites with the same coordination number, the moment tends to decrease as the number of Cu neighbors increases. As a consequence, in Co agglomerates, the magnetic moment decreases considerably as one goes from more central sites to those close to the grain boundary at the Co–Cu interface.