High-Frequency Soft Magnetic Properties of Isotropic Co-Al-N Films

Co-Al-N films with wide Co compositional range were prepared by the rf-sputtering method in order to obtain soft magnetic properties at high frequencies. The films consisted of Co nano-granules 3-5 nm in diameter, randomly dispersed in an AlN amorphous matrix. Ferromagnetic properties were obtained in the film with a Co content of 47-80 at.%. The films were shown perpendicular magnetic anisotropy with coercivity around 20-50 Oe, and had the same magnetization curve in all film plane directions. Co-Al-N films showed an excellent frequency response of permeability. The permeability (μ) of Co ₈₀Al ₁₄N ₆ film, in particular, was constant up to 1 GHz, and exhibited a clear peak at the resonance frequency (fr) at around 1.2 GHz. The origin of this specific μ -f response of isotropic Co-Al-N films with perpendicular magnetic anisotropy can be attributed to the rotatable magnetic anisotropy.