Change in coercive force of γ-Fe2O3-Fe3O4solid solutions with magnetostrictive anistropy

γ-Fe2O3-Fe3O4solid solutions with several degrees of reduction from γ-Fe2O3were prepared to study the effect of magneto-strictive anisotropy on coercive force. Changes in the coercive force are observed in the temperature range from liquid nitrogen temperature to room temperature when the magnetic powder is surrounded with materials such as paraffin and epoxy resin. It is found that the change in the coercive force is proportional to the magnetostriction measured for disk samples of magnetic oxide powder.