MAGNETIC HYSTERESIS OF PSEUDO-SINGLE-DOMAIN AND MULTIDOMAIN MAGNETITE BELOW THE VERWEY TRANSITION

Abstract

Hysteresis loops have been measured as a function of temperature between 10 K and room temperature for two size fractions of crushed magnetite: 1–5 μm (pseudo-single-domain, PSD) and 100–150 μm (multidomain, MD). The material under study appears to be fairly close to stoichiometric magnetite, with a Verwey transition temperature of 115 K for the MD sample and 118 K for the PSD sample. For both samples, hysteresis properties below the Verwey transition depend critically on whether or not the samples were cooled through the transition in the magnetic field. For the PSD sample, an even more complex behavior has been observed: temperature dependences of coercive force obtained after zero-field-cooling differ significantly for the demagnetized versus magnetized starting magnetic state.