rf-diode-sputtered iron nitride films for thin-film recording head materials

We have obtained iron nitride films with a saturation magnetization of 21 kG, coercivity less than 1 Oe, and hard axis permeability of 4000. The saturation magnetostriction decreased as input power increased, or as the N2/Ar flow rate ratio decreased. X-ray analysis revealed that an increase in input power or a decrease in the flow rate ratio resulted in less γ′-Fe4N phase in the films deposited. The coercivity was also very sensitive to these variations. The iron nitride films did not show structural changes under vacuum annealing from 150 to 300 °C, but their coercivity decreased slightly. The coercivity increased rapidly after annealing above 350 °C, however.