The magnetooptic Kerr effect (MOKE) is a well known and handy tool to characterize ferro-, ferri-and antiferromagnetic materials. Many of the MOKE techniques employ effects solely linear in magnetization M . Nevertheless, a higher-order term being proportional to M 2 and called quadratic MOKE (QMOKE) can additionally contribute to the experimental data. Here, we present detailed QMOKE spectroscopy measurements in the range of 0.8 -5.5 eV based on a modified 8-directional method applied on ferromagnetic bcc Fe thin films grown on MgO substrates. From the measured QMOKE spectra, two further complex spectra of the QMOKE parameters Gs and 2G44 are yielded. The difference between those two parameters, known as ∆G, denotes the strength of the QMOKE anisotropy. Those QMOKE parameters give rise to the QMOKE tensor G, fully describing the perturbation of the permittivity tensor in the second order in M for cubic crystal structures. We further present experimental measurements of ellipsometry and linear MOKE spectra, wherefrom permittivity in the zeroth and the first order in M are obtained, respectively. Finally, all those spectra are described by ab-initio calculations.

We investigated crystallographic and magnetic properties of TiN buffered Co2FeAl thin films. Room temperature deposition of the Heusler compound led to high crystalline ordering. The layer thickness and post annealing temperature dependence of the coercivity, squareness ratio, and the anisotropy constant of the thin Co2FeAl films were measured. High perpendicular magnetic anisotropy was observed for the 0.9 nm thin Co2FeAl film. A squareness ratio of one was reached at 325 °C post annealing temperature, which is lower compared to previous studies. It remained constant for temperatures up to 500 °C. Surface sensitive x-ray absorption and x-ray magneto circular dichroism measurements were carried out, in order to investigate the element specific magnetic moments. A magnetic moment of 5.4 ± 0.4 μB/f.u. for the 1 nm thin Co2FeAl was determined, which is in good agreement with the previously reported values for Cr or MgO buffered Co2FeAl.

The Heusler compound Co 2 MnSi provides a crystallographic transition from B2 to L2 1 structure with increasing annealing temperature T a , 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 M 2 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 Co 2 MnSi thin films deposited on MgO(001) substrates and annealed from 300 • C to 500 • C. The amplitude of LinMOKE and QMOKE spectra scales linearly with T a , 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 Co 2 MnSi up to the second order in M , are obtained dependend on T a . Finally, the spectra are compared to ab-initio calculations of a purely L2 1 ordered Co 2 MnSi Heusler compound.