Measurements of critical exponents and the magnetic equation of state in Fe3O4 by polarized neutron scattering

A new method for measuring static critical indices in magnetic materials is proposed, tested and shown to be feasible. The method is based on the scattering of polarized neutrons which provides the only possibility for accurately measuring the critical indices β, γ and delta by neutron scattering. The method has been used in a study of the magnetic phase transition in Fe3O4, for which the critical indices of each of the two sublattices were measured and found equal. By appropriate scaling it has been possible to obtain a magnetic equation of state curve for the substance at T>Tsub(c). The results have been discussed in the context of universality and scaling. (Auth.)