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 (Co sub 93 Zr sub 7 ) sub 100--y RE sub y (RE = neodymium, praseodymium, dysprosium, terbium, gadolinium, or samarium: magnetic rare earth elements) have been prepared. 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 H sub k appears, whose magnitude depends upon composition and preparation parameters. Above a critical substitution level, a biaxial anisotropy exhibiting an in-plane H sub k and a perpendicular component H sub p 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 H sub k and H sub p . 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 results on films exhibiting uniaxial or biaxial anisotropy are reported and discussed.