Magnetic Anisotropy and Rotational Hysteresis in Single Crystals of Magnetite below the Transition Temperature

Abstract

Torque curves have been measured at 82°K on gallium- and aluminium-substituted single crystals of magnetite. The paper consists of two parts, one dealing with the values of the constants required to describe the intrinsic anisotropy of Fe₃O₄ below the crystallographic transition and the other concerned with the irreversible nature of the torque curves observed on some of the gallium-substituted crystals. A model based on the ordering of Fe²⁺ and Fe³⁺ ions is proposed to explain this rotational hysteresis which occurs in higher fields than would be necessary for magnetic saturation.