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

The magnetic and related structural properties of amorphous ${\mathrm{Co}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Ti}}_{\mathrm{x}}$ ferromagnetic thin films are reported. The concentration range investigated is 0.14≤x≤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 $K_u$ ($K_u$ ${)}_{\max }$ 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.