Controlling the induced anisotropy in soft magnetic films for high frequency applications

Summary form only given. Soft magnetic materials with controllable uniaxial anisotropy are required for future ultrahigh frequency applications. Nowadays, the attention is focused on FeXN (X = Ta, Zr, Al). systems due to their high saturation magnetisation, excellent magnetic softness and good corrosion resistance. The films can be obtained in an as-deposited nanocrystalline state by sputtering Fe rich alloys in a reactive atmosphere (Ar + N/sub 2/). Such materials can be magnetically soft when the grain size becomes smaller than the ferromagnetic exchange length (as explained by the random anisotropy model). The anisotropy is created by a bias magnetic field applied during deposition or during a subsequent annealing. One limiting factor restricting the frequency range of applications is the natural ferromagnetic resonance. In order to push this limit in the GHz range, films with a uniaxial anisotropy field in excess of 20 Oe are desired. We have obtained films with excellent soft magnetic properties and controllable in plane uniaxial magnetic anisotropy by depositing Fe N films at different substrate temperatures. The induced in-plane anisotropy increases with increasing nitrogen content. Increasing the Zr/Fe ratio from 1/99 to 3/97 has little influence on the induced anisotropy.