Quadratic magneto-optical Kerr effect in Co₂MnSi

Quadratic magneto-optical Kerr effects (QMOKE) are investigated in epitaxial Co₂ MnSi thin films as a function of the post-deposition annealing temperature. We determine the amplitude of the QMOKE signal for different annealing temperatures, which provide various degrees of L2 ₁ crystal ordering, as manifested by X-ray diffraction. We observe that QMOKE is significantly present only when the L2₁ ordering phase is also present, and that the QMOKE signal increases with the higher degree of L2₁ ordering. Additionally, we notice that the linear magneto-optical Kerr effect (LMOKE) decreases with higher annealing temperature. A comparison of the linear and quadratic MOKE contributions shows the amplitudes are of similar magnitude. From these results, we conclude that the presence of QMOKE is linked to the higher degree of L2₁ ordering in Co₂ MnSi.