Probing the electronic structure of Ni-Mn-In-Si based Heusler alloys thin films using magneto-optical spectra in martensitic and austenitic phases

摘要

Thin films of Ni_(52)Mn_(35−) _xIn_(11+) _xSi_2 were fabricated by magnetron sputtering on MgO (0 0 1) single crystal substrates. Magnetization as function of temperature for Ni_(52)Mn_(35)In_(11)Si_2 exhibits features consistent with a magnetostructural transition (MST) from an austenitic phase to a martensitic phase, similar to the bulk material. We observed that the martensitic transformation is externally sensitive to small changes in chemical composition and stoichiometry. It has been found that thin films of Ni_(52)Mn_(34−) _xIn_(11+) _xSi_2 with x = 0 and 1 undergo a temperature-induced MST or remain in a stable austenitic phase, respectively. Comparison of magneto-optical transverse Kerr effect spectra obtained at 0.5-4.0 eV in the 35-300 K temperature interval reveal insignificant differences between the martensitic and austenite phases. We found that the field and temperature dependencies of the transverse Kerr effect are quite different from the magnetization behavior, which is attributed to magnetic inhomogeneity across the films. To elucidate the effects of magnetostructural phase transitions on the electronic properties, we performed density functional calculations of the magneto-optical Kerr effect.