High-nitrogen-concentration FeTaN films have been newly developed as a high performance magnetic head core material. 10.5–14.5 (at. %) N, 8–13 Ta, and balance Fe composition films, prepared by a nitrogen reactive sputtering method followed by appropriate annealing (500–550 °C), have high saturation flux density (14–17 kG) and excellent soft magnetic properties: such as low coercivity (∼0.1 Oe), high relative permeability (3000 at 20 MHz), and small saturation magnetostriction ( < 0.5 × 10−6). Fine crystal structure is one of the most essential origins for the soft magnetism of FeTaN films. The FeTaN films are expected to realize recording density increases and rubbing noise reduction with high durability and high reliability due to their high Vickers hardness (1000) and their higher corrosion resistance than Sendust film.

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FeN phase generation has been observed by x-ray analysis in FeTaN films, which normally show α-Fe, TaN phase, and no FeN phases. With a rise in substrate temperature Ts above 200 °C, FeN phases are generated in nitrogen reactive sputtering process with columnar structure formation, and remain after annealing. With FeN phase generation, coercivity Hc and magnetostriction λ values increase markedly. Moreover, internal stress σ for the films increases drastically. The FeTaN films, sputtered on low temperature substrate, generate no FeN phases, and show low Hc, about 0.1 Oe, and low λ. Consequently, FeN phase generation with columnar structure formation has negative effects for FeTaN films to be used as magnetic head core materials. For preparation of FeTaN films, the substrate temperature has to be controlled to a sufficiently low value for suppression of FeN phase generation.

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