Microcrystalline Fe-M-C (M = Ti, Zr, Hf, V, Nb, Ta) films crystallized from the amorphous state are suitable for use in magnetic heads. Crystallization of such films is supposed to be initiated by nucleation of fine carbides of the element M, because of the strong affinity of M for carbon. The precipitated Fe-rich phase was found to be a supersaturated solid solution with a tetragonally deformed lattice, and it gradually changes to the bcc phase as the annealing temperature increases. In these alloys, the change in soft magnetic properties with annealing temperature seems to be strongly affected by grain size rather than by changes in crystal structure or magnetostriction. The coercivity increased at high annealing temperatures caused by grain growth of Fe. The upper limit to the annealing temperature is as high as 1000 K for Fe-Hf-C and Fe-Ta-C films, for which the crystallization temperature is relatively high.
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