Mössbauer effect in the system Sr1–xLaxFeO3

Abstract

Mössbauer spectra at room temperature of samples in the system Sr_1–xLa_x FeO₃ show a single absorption peak for x= 0.2–0.6 having an isomer shift intermediate between that of iron(III) and iron(IV). This is the result of an electronic exchange which is rapid compared to the lifetime of the excited state of ⁵⁷Fe. Consequently, the Mössbauer effect is indicative of an average oxidation state. At 78°K, however, Mössbauer spectra of these samples show magnetic hyperfine splitting and the individual oxidation states are readily resolved. The temperature dependence of the Mössbauer effect is indicative of the onset of the rapid electronic transfer and it is discussed with respect to the different phases within the system.