Coercive Force of Iron Oxide Micropowders at Low Temperatures

Publisher Website
Google Scholar
Abstract
The coercive force of some magnetite and gamma-ferric oxide micropowders has been measured in the temperature range 77°K to 300°K. Some of the powders contained essentially only single-domain acicular particles, others contained only multidomain particles. For the former, the results are consistent with an interpretation based on the usual relationship between coercive force and the anisotropies; for the latter with an interpretation based on the variation of the crystalline anisotropy constant with temperature. In addition, a new memory effect has been observed for the multidomain magnetite powders. If a sample was placed in some state of magnetization below the transition temperature, warmed to room temperature and then recooled, the measured value of the coercive force depended on this original state.