Magnetism of iron clusters embedded in cobalt

We present a theoretical study of the spin magnetization of iron clusters embedded in a cobalt matrix. The calculations are performed on a large bcc cluster of 1021 atoms comprising an n atom iron core and a (1021-n) atom cobalt coating, where n is varied from 59 to 641. The work is based on a spin-polarized tight-binding Hamiltonian. Comparison is made with the magnetization of FeₙCu_1021-n clusters. It is found that in the copper matrix, the moments on the iron are reduced to a value close to that of bulk iron, whereas in a cobalt matrix, the iron moments are very similar to the values found in free iron clusters, in good agreement with recent experiment results. Interestingly if some alloying of the iron and cobalt is allowed in the region of the interface, we obtain an enhancement in the iron moment as compared to that of a free iron cluster of a similar size.