INFLUENCE OF PREPARATION PROCESS ON CRYST AL-STRUCTURE AND CORROSION-RESISTANCE OF FE-HF-N SOFT-MAGNETIC THIN-FILMS

The influence of the composition and preparation conditions on the cor rosion resistance and the crystal structure of Fe-Hf-N soft magnetic t hin films is studied to obtain a soft magnetic material with Bs over 1 .5 T. The best corrosion resistance mas obtained for the Fe-Hf-N film, deposited in sputtering gas with 8 vol%N-2. In this case, the grain s izes of the Fe crystals in the film are small, which is supposed to be the main cause of the good corrosion resistance. The films prepared u sing sputtering gas containing 12 vol%N-2 are susceptible to corrosion , due to the excessive growth of the Hf-N grainss. The films prepared with higher RF power show a larger Fe 110 peak in X-ray diffraction, w hile they get weaker against corrosion. The films prepared at higher s puttering gas pressure show larger Fe and Hf-N grains, while their cor rosion resistance remains unchanged. The change in the annealing tempe rature between 773 and 863 K does not influence the crystal structure nor the corrosion resistance of the films. After optimization of the c omposition and preparation conditions, a film was obtained with Bs = 1 .5 T, Hc = 48 A/m, lambda s = 3 x 10(-6) and mu = 2000 (at 1 MHz) at t he composition of Fe70.5Hf11.0N18.5 after annealing at 823 K.