Structural, electrical transport and x-ray absorption spectroscopy studies of LaFe1-xNixO3 (x≤0.6) -: art. no. 093526

Electronic structures of LaFe1-xNixO3 (x <= 0.6) have been studied by x-ray absorption near edge structure spectra of O K, Fe L-2,L-3 and La M-4,M-5 edges. Upon substitution of Ni at Fe site in LaFeO3, the O K-edge spectra show a feature about 2.0 eV lower than that of LaFeO3. This feature is growing as the concentration of Ni is increasing. This is consistent with our resistivity data which show that the resistivity decreases very fast with Ni substitution from G Omega cm for LaFeO3 to a few m Omega cm for the sample with 60% Ni substitution. The resistivity data have been fitted with a variable-range hopping model and it is found that the gap parameter reduces from 2 eV to 2.1 meV with the Ni substitution. This gap parameter decreases very systematically with the increase in Ni concentration. The structural analysis of these samples shows that they have single-phase orthorhombic structure with space-group Pnma in the studied range (0 <= x <= 0.6). The study of Fe L-2,L-3-edge structures confirm the trivalent state of Fe. The observed features have been explained on the basis of charge-carrier doping in LaFeO3. The disorder-induced localization is found to effectively control the resistivity behavior. (C) 2005 American Institute of Physics.