Magneto-optical properties of amorphous terbium-iron alloys

The magneto-optical properties of rf sputtered amorphous Tb _xFe_1-x alloys (with 0.17≤x≤0.32) were investigated using reflectivity and polar Kerr measurements from a surface overcoated in situ with SiO₂. The concentration dependence of the Curie temperature, compensation temperature, and low-temperature polar Kerr amplitude were all derived and the results compared with a mean-field theory. The temperature behavior of the coercive force was also determined. While a considerable degree of agreement is obtained with earlier work, it appears that the low-temperature polar Kerr amplitude can only be determined by the iron sub-network alone, if the iron moment increases with terbium concentration. The extent to which this view is justified is examined in light of current ideas.