Scaling of quadratic and linear magnetooptic Kerr effect spectra with L21 ordering of Co2MnSi Heusler compound
Abstract
The Heusler compound Co2MnSi provides a crystallographic transition from B2 to L21 structure with increasing annealing temperature Ta, being a model system for investigating the influence of crystallographic ordering on structural, magnetic, optic, and magnetooptic (MO) properties. Here, we present quadratic magnetooptic Kerr effect (QMOKE) spectra depending on M2 in addition to the linear magnetooptic Kerr effect (LinMOKE) spectra being proportional to M, both in the extended visible spectral range of light from 0.8\,eV to 5.5\,eV. We investigated a set of Co2MnSi thin films deposited on MgO(001) substrates and annealed from 300 to 500. The amplitude of LinMOKE and QMOKE spectra scales linearly with Ta, and this effect is well pronounced at the resonant peaks below 2.0\,eV of the QMOKE spectra. Furthermore, the spectra of the MO parameters, which fully describe the MO response of Co2MnSi up to the second order in M, are obtained dependend on Ta. Finally, the spectra are compared to ab-initio calculations of a purely L21 ordered Co2MnSi Heusler compound.