Dilution effects on X-ray photoelectron spectra of La0.8Sr0.2MnO3 with SiO2

Abstract

Diluted samples of La0.8Sr0.2MnO3 with SiO2 were prepared by calcination of the MCM-41 molecular sieve soaked in precursor solutions with various concentrations (0.1, 0.05 and 0.005 mol/l). The diluted samples from the 0.1, 0.05 and 0.005 mol/l solutions showed ferromagnetic behavior in temperature dependent magnetic susceptibility below ≈300, ≈250 and ≈100 K, respectively. The electron binding energy of the La 3d5/2 main peak of the diluted samples from the 0.1, 0.05 and 0.005 mol/l solutions were 835.7, 836.0 and 837.4 eV, respectively, and were larger than that of La0.8Sr0.2MnO3 bulk sample (834.2 eV). Reduction in intensity of the La 3d charge-transfer satellite was more pronounced for more diluted sample. The Mn 2p3/2 main peak of all the diluted samples remained at 642.2 eV, which is larger by 0.6 eV than that of the bulk sample (641.6 eV). The charge-transfer peak energy in the optical absorption spectra was the same (2.3 eV) for all the diluted samples, and the energy was larger by 0.4 eV than the bulk one (1.9 eV). The dilution caused localization of charge carriers within the La0.8Sr0.2MnO3 lattices isolated by the insulator. Suppression of charge flow between the isolated La0.8Sr0.2MnO3 lattices resulted in the enlargement of the La 3d electron binding energy and the decrease of the La 3d charge-transfer satellite peak intensity, and also the lowering of the ferromagnetic ordering temperature. © Springer Science + Business Media, Inc.