Mössbauer Studies on Iron in the Perovskites ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x\mathrm{Fe}{\mathrm{O}}_3 (0\mathrm{}<~x<~1)$

Mössbauer spectra of the perovskite series ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x\mathrm{Fe}{\mathrm{O}}_y (0.0\mathrm{}<~x<~1.0);y\lesssim 3)$ with ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ as the photonemitting and -absorbing nucleus were analyzed. The Néel temperature of antiferromagnetic LaFe${\mathrm{O}}_3$ decreases with increasing Sr concentration. Characteristic ${\mathrm{Fe}}^{4+}$ lines for high $x$ have isomer shifts between +0.10 and +0.20 mm/sec relative to a source of ${}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$ in stainless steel. However, for intermediate $x$ a ${\mathrm{Fe}}^{3+\leftrightarrow 4+}$ mixed state seems to exist. Increasing $x$ causes a significant discontinuity in the total isomer shift (transition from magnetic order to disorder). Linewidths vary around 0.40 mm/sec and show broadening in a sample fired briefly.