Magneto-optical investigation of epitaxial nonstoichiometric Co2MnGe thin films

We investigate the magneto-optical properties of a nonstoichiometric, epitaxial Co2Mn0.77Ge0.42(001) film grown on a MgO-buffered MgO(001) single-crystal substrate. Magneto-optical Kerr effect magnetometry indicates that the sample has strong uniaxial anisotropy, whereas the easy and hard axes of magnetization are tilted by ∼10° with respect to the [110] and [110] directions, respectively. A modest quadratic Kerr effect with an amplitude of 0.4 mdeg was observed. Brillouin light scattering spectroscopy was used to find that the exchange constant A, spin-wave stiffness D, and saturation magnetization Ms are 22.5 pJ/m, 413 meV Å2, and 6.43 μB/f.u., respectively. The saturation magnetization value suggests that the Slater-Pauling rule might apply to such nonstoichiometric compositions.