POLARONIC TRANSPORT-PROPERTIES IN LA1-XSRXFEO3 SYSTEMS LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.3)

Electrical transports in the La1-xSrxFeO3 system (0.05 less than or eq ual to x less than or equal to 0.3) was investigated as a function of temperature from 80 K to 350 K by dielectric properties, DC and AC con ductivities. Two dielectric relaxation peaks appeared and their relati ve peak heights were closely related to the amount of Sr. The intensit ies of both these peaks were thermally activated. In every specimen, t here was an Arrhenius relation between sigma T and T, the activation e nergy of which was nearly equal to the sum of the activation energy re quired for the dielectric relaxation and that for the thermal activati on in the intensity of the relaxation peak The frequency dependences o f AC conductivities obeyed an equation of sigma(omega) = A omega(s) an d AC conductivities were independent of temperature below similar to 2 00 K at every applied frequency. These results were explained self con sistently with small polarons of ligand holes (3d(5) ($) under bar L) which were transformed from the states of O 2p weight to the mixed Fe 3d-O 2p states with an increase in the covalent character as the amoun t of Sr increases, as confirmed by the soft-x-ray spectroscopies and X PS-experiments.