Easy axis dispersion in high moment Fe-Co-Ni thin films electrodeposited on various underlayers

Summary form only given The high frequency performance of write heads depends on the easy axis dispersion of the pole materials. in this work soft, high moment Fe-Co-Ni films (50-1200 nm thick) were electrodeposited on non-magnetic (100 nm Cu), ferromagnetic F (100 nm Fe/sub 20/Ni/sub 80/), antiferromagnetic AF (10 nm FeMn), and composite AF/F (F on top) underlayers in order to investigate the influence of F and AF coupling on the easy axis dispersion. Underlayers were DC sputtered onto a Si substrate, without stripping its native oxide. The influence of the underlayers on alloy composition, structure and magnetic properties - in particular, dispersion of the easy axis, coercivity and anisotropy field - was investigated. Film composition (as determined by EDX) was approximately constant at Fe/sub 33/Co/sub 47/Ni/sub 20/ (at %) down to a thickness of /spl sim/ 200nm. Below this thickness, Ni content increased slightly and Fe content correspondingly decreased. All films exhibited mixed FCC/BCC phases, with the relative amount of FCC phase increasing with thickness. In all cases, an increase in saturation magnetization Ms with decreasing thickness was observed. Films grown on Cu or FeMn exhibit an open hard axis loop, with coercivity H/sub c/ /spl sim/ 4 Oe. FeCoNi films on Fe/sub 20/Ni/sub 80/ underlayer exhibit a well-defined uniaxial anisotropy, M/sub s/ /spl sim/ 21 kG, easy axis H/sub c/ =1.5 Oe, anisotropy field H/sub k/ /spl sim/ 20 Oe, and very small hard axis hysteresis. Films grown on FeMn/Fe/sub 20/Ni/sub 80/ underlayers show very similar properties. The Permalloy layer can thus improve the uniaxial anisotropy of FeCoNi through exchange coupling, while FeMn does not exchange couple effectively to FeCoNi, perhaps due to oxidation of the underlayer upon exposure to air prior to deposition. The permeability at 10 MHz for all films is in the range 800-1300, showing no definite dependence on the film thickness or underlayer.