On the Nature of Defects in the Magnetic Structure of Wüstite

Abstract

Neutron diffraction patterns from non‐stoichiometric $\mathrm{FeO}$ specimens obtained at 290°K and 4.2°K show the presence of defects which consist of cation vacancies on octahedral sites and interstitial cations in tetrahedral sites. The average magnetic moment per cation site is much smaller than expected. Magnetization studies show a ferromagnetic remanence is present, and the hysteresis loop is displaced along the $H$ axis. A model is proposed in which clusters of vacancy‐interstitial defect complexes form superparamagnetic islands in exchange contact with the antiferromagnetic matrix.