Magnetic properties of Fe-O thin films prepared with oxygen ion assisted vacuum deposition

Various iron oxide thin films were prepared by oxygen-ion-assisted vacuum deposition by changing the amount and energy of the ions for fixed oxygen pressure of 7×10^-5 Torr. A more highly oxidized state was realized for larger amount of ions or smaller ion energy. Maximum coercive force was realized for films consisting of Fe ₃O₄ and ferric iron oxide which has a crystallographic state intermediate between the cubic spinel and hexagonal corundum structures. Increase of the lattice constant of the spinel structure was observed, tending toward the formation of intermediate ferric oxide. The observations suggest that the main origin of the observed change of coercive force is the change of magnetocrystalline anisotropy induced by isotropic stress