A study on Hc-enhancement in Co-modified γ-Fe 2O 3

We have investigated the effects of valence states and Co-distributions on the coercivity of particulate and thin film Co-treated γ-Fe ₂O ₃. A maximum H_c of 2 kOe has been obtained in thin films prepared by a new simple method. We found that Co-ions exist in the divalent states probably in the form of ferromagnetic CoFe ₂O ₄ and that simple CoO to γ-Fe ₂O ₃ interfaces do not appear to enhance H_c. On the other hand, we observed complex diffused interfaces in a thin film sample with enhanced H_c. The diffused interfaces may be responsible for the H_c-enhancement in Co-modified γ-Fe ₂O ₃ recording media.