Monte Carlo simulation of surface anisotropy in La2/3Ca1/3MnO3 nanoparticles

Using Monte Carlo methods, the thermally activated magnetic property switching of nanoparticles was studied. The analysis was applied to nanoparticles of La2/3Ca1/3MnO3, and the results were compared with bulk material properties. The model is based on a three-dimensional classical Heisenberg-Hamiltonian involving the presence of Mn3+eg, Mn3+eg′ and Mn4+ ions and their nearest-neighbor interactions. For this model, simple cubic lattice samples were employed. Nanoparticles with diameters between 2.316 nm (6 ions) and 10.422 nm (27 ions) were simulated. A shift in the transition temperature (Tc=260 K) was observed with respect to the bulk value. This shift is due to the surface anisotropy, which can be explained by the finite size scaling theory.