Search for high moment soft magnetic materials: FeZrN (abstract)

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Abstract
FeN materials exhibiting high moment, low coercivity and small magnetostriction have previously been reported. Zr has been known to reduce the magnetostriction in other Fe alloys. The criteria for an ideal recording head pole material as well as shields for magnetroresistive sensors include high moment, low coercivity, high permeability, and zero magnetostriction. We present here the properties of half micrometer thick rf sputtered FeZrN films on glass coupons. The films were deposited at a pressure of 3 mTorr using a Perkin–Elmer sputtering system. The target was composed of Fe with Zr chips covering approximately 2% of the surface area. The properties were measured as a function of the N2 partial pressure. The saturation magnetization of the as-sputtered films was approximately 20 kG. The easy axis and the hard axis coercivities show minima at approximately 7%–10% N2 partial pressure of approximately 1.8 and 0.6 G, respectively. The magnetic anisotropy is approximately 5 G yielding a dc permeability of approximately 4000 along the hard axis. X-ray data reveal a systematic change in the ratio of α-Fe and γ-Fe4N; the amount of the γ-Fe4N phase increases with increasing N2 flow rate. The magnetostriction increases with increasing N2 content crossing zero at approximately 6%. The grain size as probed by atomic force microscopy is an increasing function of the N2 partial pressure, from a few nm for a N2 partial pressure of 5% to as large as 50 nm for a N2 partial pressure of 15%.