In3+ substitution effects and defect distribution in Li0.25Mg0.5Mn0.1Fe2.15-xInxO4 studied by positron annihilation and Mossbauer spectroscopy

The ferrite series Li0.25Mg0.5Mn0.1Fe2.15-xInxO4 (x = 0, 0.3, 0.6, 0.9) have been studied through positron lifetime and Mossbauer spectroscopic techniques. The changes in positron lifetime parameters are attributed to positron trapping in tetrahedral and octahedral sites at the different stages of In3+ ion substitution. Positrons initially get trapped in the vacancies in the octahedral sites in the undoped sample. With doping by In3+ ions up to x = 0.3, tetrahedral vacancies dominate as positron trapping sites. With further doping, some of the octahedral sites become vacancies and trap positrons. Incorporation of In3+ ions in the place of Fe3+ ions in the series has also introduced magnetic dilution in both the tetrahedral (A) and octahedral (B) sites. Knowledge of the variation in the magnetic properties of these ferrites with increase in concentration of In3+ ions, as derived from the Mossbauer parameters, suggests a correlation of such a variation with the defect concentration in these samples. (C) 2004 Elsevier B.V. All rights reserved.