Low-temperature viscous magnetization of multidomain magnetite: Evidence for disaccommodation contribution

Low-temperature viscous acquisition and decay measurements above and below the Verwey transition have been carried out for a selection of natural and synthetic multidomain magnetite samples. A strong correlation between the viscosity spectra and published disaccommodation spectra was found, where disaccommodation reflects electron mobility. Assuming the viscosity is controlled by identical mechanisms as disaccommodation, the reduction in electron mobility below the Verwey transition is found to significantly increase viscous acquisition and decay rates over the time scales measured (1-3000 s). Although strongly affecting the viscosity, disaccommodation processes do not appear to control the rate of change of viscosity with time, i.e. the viscosity curvature. It is suggested that the curvature is controlled by the shape of relaxation-time distributions, which is approximately the same for all the magnetite samples studied. In addition, the acquisition and decay curvature parameters mirror each other when plotted as a function of temperature, inferring that at any given temperature, the acquisition and decay processes are identical.