Local interactions and electronic phenomena in substituted LaFeO3 perovskites

Effects of electronic charge disproportionation were observed by 57Fe Mössbauer spectroscopy at low temperatures in substituted LaFeO3 perovskites as (La1−xCax)FeO3 and La(Fe1−xMgx)O3 (x≤0.5). The presence of both Fe3+ and Fe5+ species was evidenced in both series of compounds. Direct evidence for disproportionation was supported by correlating the Mössbauer results with the chemical determination of tetravalent iron at RT. The evolution of hyperfine parameters vs. substitution degree was comparatively analysed for Fe3+ and Fe5+ ions in relation to their electronic microscopic origin. Electron delocalisation processes are discussed in terms of ion distribution and valence state.