Mössbauer Studies of the System La1−xSrxCo1−yTiyO3

Abstract

The system La1−xSrxCo1−yTiyO3 for (a) x = 0 and (b) x = y is investigated through Mössbauer spectroscopy measurements carried out between 77 and 800 K. None of the Mössbauer spectra show hyperfine splitting even at 77 K as Ti4+ substitution restricts the generation of Co+ which is primarily responsible for itinerant electron ferromagnetism in La1−xSrxCoO3. In all the samples, two resonances are observed except in the samples with y = 0.3 and 0.5 in the system (a) where three resonances are observed. Three resonances are assigned to low spin cobalt states (i.e. CoII, CoIII and CoIV), high spin Co3+(t2g4eg2) and high spin Co2+(t2g5eg2) states, the first two being common in all the samples. The variation of the isomer shift and other data with temperature is discussed in the framework of spin‐state and valence‐state equilibria of cobalt ions in these materials. The difference in behaviour between the systems (a) and (b) is explained in terms of generation of different valence and spin states of cobalt with the increase in x and is further compared with the system La1−xSrxCoO3. The susceptibility, electron transport, and other data reported earlier support the results obtained from Mössbauer studies. Copyright © 1985 WILEY‐VCH Verlag GmbH & Co. KGaA