Spin-wave resonance and magnetic properties in amorphous Co95-xZr5Mx (M=Zr,Nb,Ti) and Co91-xZr9Ptx thin films.

Abstract

Amorphous ${\mathrm{Co}}_{95\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Zr}}_{5}$${\mathit{M}}_{\mathit{x}}$ (M=Zr,Nb,Ti) and ${\mathrm{Co}}_{91\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Zr}}_{9}$${\mathrm{Pt}}_{\mathit{x}}$ thin films were prepared by rf sputtering in a magnetic field applied parallel to the film surface. Here we report their ferromagnetic-resonance and magnetic properties. For the spin-wave resonance spectra corresponding to ${\mathrm{Co}}_{100\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Zr}}_{\mathit{x}}$ thin films, all the resonance fields, including the one corresponding to the uniform mode, follow a quadratic dispersion law with excellent precision. The intensities of the spin-wave mode are very weak. The overall results are fairly well explained by a model where it is shown that the characteristics of the spectra are determined by the random local anisotropy ${\mathit{K}}_{\mathit{l}}$. The value of the deduced ${\mathit{K}}_{\mathit{l}}$ decreases with decreasing ${\mathit{M}}_{\mathit{s}}$ as predicted by the single-ion anisotropy theory. The magnetic properties were studied systematically as a function of the pressure of sputtering gas ${\mathit{P}}_{\mathrm{Ar}}$ and rf input power ${\mathit{W}}_{\mathrm{rf}}$. The in-plane uniaxial anisotropy energy ${\mathit{K}}_{\mathit{u}}$ and the coercive field ${\mathit{H}}_{\mathit{c}}$ along the easy axis were dependent on the deposition parameters. The variations of saturation magnetization 4\ensuremath{\pi}${\mathit{M}}_{\mathit{s}}$ and magnetostriction ${\ensuremath{\lambda}}_{\mathit{s}}$ are also described.