High frequency properties of Fe–Cr–Ta–N soft magnetic films

High frequency magnetic properties of a new, soft magnetic Fe–Cr–Ta–N alloy film have been investigated. Thin films with a composition of Fe-4.6% Cr-0.2% Ta-7.4% N (in atomic %) were prepared by reactive sputtering in a nitrogen-containing atmosphere. The films, most likely nanocrystalline, exhibit excellent soft magnetic properties in the as-deposited condition without any post heat treatment, e.g., Hc as low as 1.2 Oe (95.3 A/m) and 4πMs∼20 kG. The easy-axis M–H loop is square. The hard-axis loop is linear and closed, with the anisotropy field Ha=20–100 Oe (1.59–7.95 kA/m). By virtue of their high 4πMs and relatively high Ha, these soft magnetic films exhibit high permeability and low loss in the GHz frequency range with the undesirable ferromagnetic resonance interference suppressed to beyond 2 GHz.