Monte Carlo study on magnetic nanoparticles from first principle

In order to study the finite temperature behavior of magnetic nanoparticles a novel Monte Carlo method has been developed. The energy of a new trial configuration during the simulation is calculated directly from the expansion of the band energy avoiding a set up of an a priori Heisenberg-type model. The electronic structure of the cluster is determined by means of the embedded-cluster Green's function technique based on the Korringa-Kohn-Rostoker method within the local spin-density approximation of the density functional theory. As a benchmark the ground state of anti-ferromagnetic clusters and the temperature dependence of the magnetization of a flat square cluster of 16 Co atoms on a Cu(001) surface have been studied.