Uniaxial and local anisotropies in amorphous thin CoZr films

RF sputtered amorphous CoZr and CoNbZr films were field-annealed in vacuum. Their uniaxial and local anisotropies as well as their saturation magnetization were investigated before and after the heat treatment. Susceptibility measurements as introduced by the ripple theory were carried out. In general, the coercive force is very low (0.1 Oe), the saturation magnetization ranges at 1000 emu/cm³for CoZr and 900 emu/cm³for CoNbZr, depending on the composition. The saturation magnetostriction λsis below 3.10^-6. Isothermal hard axis annealing of CoZr films reveals three different sources of the anisotropy: i) a non reversible part with low activation energy, ii) two reversible contributions with different relaxation times.