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.

Fe75−xMn25Gax Heusler-like compounds were investigated in a wide range of Fe/Ga ratios while keeping the Mn content constant and equal 25 at% in order to elucidate the interplay between magnetic properties and composition. Materials were prepared by arc-melting from pure elements and subsequently annealed. Experimental investigations were focused on magnetization behavior in a wide temperature range from 4 to 1000 K and magnetic field up to 9 T. Optical and magneto-optical (MO) measurements were employed to shed more light on the magnetic state and electronic structure of investigated materials. Magnetization measurements indicated that in the vicinity of stoichiometry (Fe2MnGa) the compounds are ferro/ferrimagnetic, whereas the Fe-deficient compound is paramagnetic and at high Fe concentration the antiferromagnetic interaction prevails. Theoretical calculations of corresponding ordered and disordered stoichiometric compounds were carried out and compared to the experiment on the level of net magnetic moment as well as magneto-optical spectra. This comparison suggests that the Heusler crystal structure, L21, is not present even close to stoichiometry. Moreover, the comparison of density of states (DOS) for ordered and disordered structures allowed us to explain missing martensitic transformation (MT) in investigated materials.

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Ni2MnGa is a ferromagnetic shape memory alloy in which a large spontaneous deformation up to 12% has been observed after application of an external magnetic field [1]. [...]

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