Magneto‐optic Kerr effect of amorphous Gd–Fe–Co films

Amorphous Gdx(Fe1−yCoy)1−x (0.25<x<0.28, 0<y<0.39) films have been prepared by coevaporation technique. The films exhibit the magnetization perpendicular to the film plane, and the Curie temperature rises with increasing Co content. The magneto‐optic polar Kerr rotation angel θk has been measured in the temperature range of 300–450 K. It is found that Co substituted films exhibit larger θk than Gd–Fe films in the wavelength range of 400–700 nm. The effect of Co substitution is very significant in high temperature range because of the high Curie temperature. The temperature dependence of θk can be fitted to magnetization of 3‐d transition metal sublattice using the mean field model, while the increase of θk at ambient temperature cannot be attributed to the rise of the Curie temperature.