Thickness Effect on the Magnetic Properties of Fe3O4-γFe2O3 Intermediary Films

Single-phase Fe₃O₄ thin films between 0.06 and 0.3 μm thick were formed on alumite-covered Al alloy substrates by reactive sputtering, were partially oxidized by annealing in air to obtain Fe₃O₄-γ-Fe₂O₃ films, and the magnetic and other properties of the latter were studied. It was found that while more complete oxidation acts to raise the film coercivity, M_r/M_4k and S*, when films are made thinner the extent of these increases is reduced. Also, the Hcmax value is considerably influenced by the initial state of the Fe₃O₄ film.