Experimental evidence of the electronic transitions responsible for magneto-optical activity of La1−xSrxMnO3 (x⩽0.25)

The spectral, field and temperature dependences of magneto-optical Kerr effect (MOKE) in ferromagnetic La1−xSrxMnO3 single crystals with x=0.15x=0.15, 0.20 and 0.25 were studied. The measurements were carried out before and after recovery annealing in air or argon atmosphere. It was found that the shape and behavior of MOKE(T) curves are strongly dependent on x and the annealing conditions. The components of the permittivity tensor were calculated. Two transitions with different temperature dependences were allocated within the energy region 2.5–4.0 eV. The features of MOKE spectra are connected with charge transfer transitions in [Mn3+O6]-octahedral complexes with different valence. The independence of the MOKE and the permittivity tensor spectra of doping level at low temperatures is interpreted in the assumption of localization of doping holes at oxygen ions in the x<0.25x<0.25 samples.