MOSSBAUER STUDIES ON THE SERIES LA1-XSRXFEO3

Mossbauer spectra have been recorded at 4.2 and 300 K on the series La 1-xSrxFeO3, where x varies from 0 to 1.0 in steps of 0.1. Neutron diff raction experiments have shown that the crystal structure is orthorhom bic for 0 less than or equal to x < 0.3, rhombohedral for 0.4 less tha n or equal to x less than or equal to 0.7, and cubic for 0.8 < x less than or equal to 1.0. Mossbauer spectra at 4.2 K are composed of magne tic sextet components arising from different charge states of iron ion s. In the orthorhombic and rhombohedral phases, the charge states Fe3 and Fe5+ coexist. In the cubic phase, iron is present as Fe3+ and Fe4 + states. At 300 K, the samples are magnetically ordered in the range 0 less than or equal to x less than or equal to 0.3 and the coexistenc e of Fe3+ and Fe5+ remains. For samples 0.4 less than or equal to x le ss than or equal to 1.0, the samples are paramagnetic. Fits to these s pectra require two components, one corresponding to an Fe4+ state, the other being best described as an Fe3+ ion for x less than or equal to 0.7 but for x > 0.7 having a mean charge state which increases to 3.5 for x = 1.0.