Magnetic and structural properties of amorphous CoTi soft ferromagnetic thin films. I. Magnetic properties.

Abstract

The magnetic and related structural properties of amorphous ${\mathrm{Co}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ti}}_{\mathrm{x}}$ ferromagnetic thin films are reported. The concentration range investigated is 0.14\ensuremath{\le}x\ensuremath{\le}0.22. In this first part of the paper the as-obtained magnetic properties are presented. The films were prepared by rf sputtering, and the deposition process was performed in a magnetic field applied parallel to the film surface. The magnetic properties were studied systematically as a function of the pressure of sputtering gas ${P}_{\mathrm{Ar}}$ and rf input power ${W}_{\mathrm{rf}}$. For the whole concentration range and the overall deposition parameters the ferromagnetic resonance revealed standing spin-wave spectra corresponding to magnetically highly uniform samples. The deposition parameters affect essentially the in-plane uniaxial anisotropy energy ${K}_{u}$ and the coercive field ${H}_{c}$ along the easy axis. ${K}_{u}$ shows a bell-shaped variation as a function of ${P}_{\mathrm{Ar}}$. The maximum value of ${K}_{u}$ (${K}_{u}$${)}_{\mathrm{max}}$ is obtained for the same ${P}_{\mathrm{Ar}}$ in the whole concentration range studied. The physical origin of ${K}_{u}$ was determined by performing thermomagnetic annealing, which revealed that depending on the value of ${P}_{\mathrm{Ar}}$ used, ${K}_{u}$ is related to a pseudodipolar or structural mechanism or a combination of both. The small variations of ${H}_{c}$ with deposition parameters are also shown and discussed in terms of the change in the local structure.