MOSSBAUER STUDIES ON THE SERIES LA1-XSRXFEO3

Mossbauer spectra have been recorded at 4.2 and 300 K on the series La1-xSrxFeO3, where x varies from 0 to 1.0 in steps of 0.1. Neutron diffraction experiments have shown that the crystal structure is orthorhombic for 0 less than or equal to x < 0.3, rhombohedral for 0.4 less than 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 magnetic sextet components arising from different charge states of iron ions. 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 coexistence of Fe3+ and Fe5+ remains. For samples 0.4 less than or equal to x less than or equal to 1.0, the samples are paramagnetic. Fits to these spectra 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.