Monte Carlo study of the bulk magnetic properties of magnetite

Within the framework of a three-dimensional Ising model with nearest magnetic neighbor interactions, and using a Monte Carlo-Metropolis algorithm for equilibrium and energy minimization, we compute the canonical ensemble averages for magnetization, magnetic susceptibility and specific heat of stoichiometric magnetite Fe3O4. In the model, atoms are distributed on an inverse spinel structure for which interactions arising from antiferromagnetic Fe-A(3+)-Fe-A(3+) Fe-A(3+)-Fe-A(3+), Fe-A(3+)-Fe-B(2+) couplings and ferromagnetic Fe-B(3+)-Fe-B(3+), Fe-B(3+)-Fe-B(2+), Fe-B(2+)-Fe-B(2+) bonds are taken into account. Labels A and B refer to tetrahedral and octahedral sites, respectively. On the basis of finite-size scaling theory, our best estimates of critical exponents for the correlation length, specific heat, magnetization and susceptibility are v = 0.65(2), alpha = 0.23(2), beta = 0.35(1) and y = 1.13(2), respectively. Simulation results as a function of temperature also allow obtaining information of the contributions per magnetic ion to the total magnetization and to the susceptibility in a differentiated fashion. (C) 2004 Elsevier B.V. All rights reserved.