Magneto-optical measurements of hysteresis loop and anisotropy energy constants on amorphous Tb_xFe_1-x alloys

Measurements of the Kerr magneto-optic effect, coercivity, and anisotropy energy constants are performed in a magneto-optical system that combines the Kerr rotation angle and ellipticity to enhance the strength of the signal. The temperature dependence of the polar Kerr effect is compared with the magnetization of the iron subnetwork in the mean-field approximation and good agreement is obtained in all cases. Coercivity is found to be a strong function of the sweeping frequency and the saturating field and the results are found to be in qualitative agreement with the magnetization reversal model based on the existence of initial nuclei in a saturated film and the subsequent growth of these nuclei under a reverse field. Finally, perpendicular magnetic anisotropy energy is studied by magneto-optical techniques and the first two coefficients in the expansion of anisotropy energy in powers of the angle of deviation from the easy axis are determined.