The optical and magneto-optical properties of ferromagnetic La(1-x)Ba(x)MnO(3) single crystals with x=0.15, 0.20 and 0.25 are studied. The components of the permittivity tensor are obtained by spectral ellipsometry techniques and transverse Kerr effect measurements. The Kerr effect spectra depend substantially on the Ba content. The plasma frequency is estimated. In the paramagnetic semiconductor state, the small polarons contribute to conductivity in La(0.85)Ba(0.15)MnO(3), in La(0.75)Ba(0.25)MnO(3) no evidence for polarons is found even in the semiconductor state. For La(0.85)Ba(0.15)MnO(3) (T(C)=214 K), the metallic phase is estimated to occupy less than 1% of the total volume at T=190 K. It is shown that in La(0.75)Ba(0.25)MnO(3), the energy gap vanishes and the metal-semiconductor transition occurs somewhat below T(C) rather than at T=T(C).

No abstract

Optical absorption and transverse Kerr effect spectra, resistivity, and magnetoresistance of La 1Ϫx Sr x CoO 3 (xϭ0.15,0.25,0.35) films have been studied. The temperature dependences of the optical and magneto-optical properties of the films exhibit features which can be attributed to the transition of the Co 3ϩ ions from the low-spin state (Sϭ0) to the intermediate-spin state (Sϭ1) and to orbital ordering of the Co 3ϩ ions in the latter state. The evolution of the properties influenced by doping with Sr is interpreted on the basis of the phase separation model.

No abstract

No abstract