A study of magnetite at 4.2 K and subject to strong applied magnetic fields

Mössbauer spectra of a powdered sample of magnetite were taken at 4.2 K and in applied fields of 0-14 T. They were fitted in accordance with specific crystallographic models of magnetite below the Verwey transition. At least five octahedral Fe 3+ sites and four octahedral Fe 2+ sites are needed to obtain both good fits and parameters which vary consistently with applied field strength. The Fe 2+ ions exhibit a large quadrupole interaction, which leads to an applied-field subspectrum of unusual shape. This shape is adequately represented by an analytic calculation for a randomly oriented electric field gradient and for magnetic moments which are collinear with the applied field.