Mössbauer Study of the Mechanical Activation Effect on the Magnetic Properties of PbFe0.5Ta0.5O3

The Mossbauer spectra of PbFe0.5Ta0.5O3 samples prepared by mechanical activation of a mixture of PbO, Fe2O3, and Ta2O5 with subsequent annealing at different temperatures Ta have been investigated. The Mossbauer study showed that Fe3+ ions in these samples can be either in the octahedral coordination or in the state with a coordination number equal to 5, which indicates the presence of oxygen vacancies in the samples. The magnetic-phase transition temperatures TM are found for all samples. The dependence of TM on Ta is peaking in the vicinity of Ta ≈ 700°C. The factors affecting the TM values of the mechanically activated PbFe0.5Ta0.5O3 samples are discussed.