Influence of conduction electrons on the magnetism of cobalt grains in a copper matrix studied by density-functional theory -: art. no. 134404

Electronic structure calculations in the local spin-density approximation were performed for clusters of 79 atoms embedded in a Cu matrix. The discrete variational method was employed. Cobalt grains of up to 55 atoms surrounded by Cu were considered; the lattice parameter of Cu was used for the calculations. Local magnetic moments and hyperfine fields were obtained for all the clusters. The results show that the local magnetic moments at the Co atom sites have oscillatory behavior with a tendency to increase in the direction of the grain boundaries. The magnitude of the contact contribution to the hyperfine field at the Co atom sites also has oscillatory behavior but with a tendency to decrease from the center to the surface of the grains. This is due to a tendency of alignment of the 4s moment with the 3d moment. Dipolar contributions to the hyperfine field were also calculated for the cobalt atoms at the boundary of the grains. The highest magnitude of this contribution was 4.2 T, Found for the grain with 13 Co atoms. Charge oscillations on Co are observed from the center to the surface.