HEISENBERG-MODEL OF SUBDOMAIN FCC CLUSTERS - A MONTE-CARLO STUDY

We show that a Heisenberg model of a spin cluster can describe subdomain ferromagnetic particles, from the dynamics of individual spins to the statistical behavior of the total magnetic moment of the cluster. While an analytical solution of the quantum spin problem is given for small clusters, a classical Heisenberg numerical simulation is used to study clusters of up to 561 atoms. We have studied magnetic behavior as a function of particle size, temperature, and magnetic field and find that the magnetization of individual clusters is well described by a Langevin function, in very good agreement with recent experiments on Co clusters in a molecular beam.