Influence of deviations from ideal stoichiometry on the anisotropy parameters of magnetite Fe3(1- delta )O4.

Abstract

Magnetization measurements are reported for ${\mathrm{Fe}}_{3(1\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}})}$${\mathrm{O}}_{4}$ in the range 0\ensuremath{\le}\ensuremath{\delta}l0.010. Anisotropy parameters consistent with these measurements were determined as a function of \ensuremath{\delta} and of temperature T both above and below the Verwey transition temperature. Analysis of the results indicates that the magnetic properties of magnetite are not solely determined by single-ion anisotropies. None of the anisotropy parameters exhibited shifts or slope discontinuities at the critical value ${\ensuremath{\delta}}_{c}$, where the Verwey transition undergoes a change in thermodynamic order; this is taken to indicate that the transition is not driven primarily by magnetic interactions.