Influence of Stress on the Coercivity of Fe₃O₄-γFe₂O₃ Intermediary Films

Abstract

The influence of stress on the coercivity of Fe₃O₄-γFe₂O₃ intermediary films has been studied. In order to induce various stresses, intermediary films were prepared on various kinds of substrates which had different thermal expansion coefficients. The surfaces of the substrates were coated with an SiO₂ layer prior to the film preparation in order to eliminate the difference in their chemical properties. The magnetic properties and plane distances of the Fe₃O₄-γFe₂O₃ intermediary films were measured. Films prepared on the substrates having smaller thermal expansion coefficients showed larger coercivity increases. A remarkable increase in coercivity was obtained only when the stress in the film was in tension.