A SIMPLE D-BAND MODEL FOR THE MAGNETIC PROPERTY OF FERROMAGNETIC TRANSITION-METAL CLUSTERS

The magnetic properties of ferromagnetic 3d transition-metal clusters have been studied by a simplified rectangular d-band model. The expres sion of local moment as a dependent function of effective coordination number for the atomic site is established by neglecting the effect of 4s, 4p electrons and presuming invariant d-band exchange splitting en ergy. The temperature effect on the magnetism has been considered on t he basis of Bloch's T-3/2 law in the mean field approximation. For Co, Ni clusters in cuboctahedral atomic-shell structures, the calculated magnetic moments are consistent with the experiments. On the other han d, the size-dependent oscillation of average moments for the Fe cluste rs is obtained by introducing the structural alternation between the c ubic bcc-like packings and the elongated or flat ones, and the corresp onding local maxima in experimental magnetic moments can be reproduced .