A study of complex permeability in rare earth-substituted cobalt/nonmagnetic transition metal amorphous thin films

By using radio‐frequency (rf) sputtering, amorphous ferromagnetic thin films of composition (Co93Zr7)100−yREy (RE=Nd, Pr, Dy, Tb, Gd, or Sm: magnetic rare earth elements) have been prepared. This work was performed for small amounts of RE substitution (y<3). These films exhibit static soft magnetic properties similar to CoZr alloys. For all compositions studied, a low in‐plane uniaxial anisotropy Hk appears, whose magnitude depends upon composition and preparation parameters. Above a critical substitution level, a biaxial anisotropy exhibiting an in‐plane Hk and a perpendicular component Hp is measured for films containing Gd or Sm. The substitution by RE atoms essentially affects the frequency‐response shape of complex permeability, depending on nature, concentration of RE atoms and on values of both Hk and Hp. High‐frequency permeability spectra could be well fitted by a theoretical model based on magnetization changes due to rotation, using a composition‐dependent Landau–Lifshitz damping term. The resu...