Effect of annealing field orientation on complex permeability spectra in Co-based amorphous ribbon

We prepare field-annealed amorphous magnetic ribbons of Co₆₆Fe₄NiB₁₄Si₁₅ at various angles, α, to the ribbon axis. The reversible and irreversible relaxation dispersions are decomposed from the complex permeability spectra in the frequency range of 1 kHz-10 MHz. Static permeabilities and relaxation frequencies for the reversible and irreversible relaxations are determined from the decomposed spectra, respectively. The irreversible permeability decreases with α and becomes negligible for α = 90°. The reversible permeability decreases as α increases for α ≤ 30°, but increases for the further increase of α > 70°. The relaxation frequency of irreversible relaxation shows a nearly constant value of 30 kHz for all samples. The relaxation frequency of reversible relaxation was 316 kHz for α ≤ 70° and increases to 724 kHz for α = 90°. The α dependence of the static permeabilities and relaxation times are analyzed in terms of the effect of easy-axis orientation on magnetization processes by domain wall motion and magnetization rotation.