X-Ray photoelectron and infrared transmission spectra of manganite system La0.5-xBixCa0.5MnO3 (0≤x≤0.25)

The results of measurements of X-ray photoelectron and infrared absorption spectra in the manganese oxides La0.5-xBixCa0.5MnO3 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25) are presented. Compared with the energy exchange splitting in different valency Mn compounds, the average Mn valency in our samples is close to 3.5+. Infrared spectra show two strong absorption bands located around 600 and 420 cm(-1), which can be ascribed to the internal phonon modes nu(s) and nu(b). As the doping x increases, the band frequency of nu(s) decreases while the nu(b) band remains invariant. and a reversal of the intensity ratio of nu(s) to nu(b) is also observed. These results reflect the changes of the Mn-O bond length and the Mn-O-Mn bond angle of MnO6 octahedra along with the doping, and the changes are mainly influenced by the unique 6s(2) lone pair character of the doped Bi ions. (C) 2002 Elsevier Science B.V. All rights reserved.