Mössbauer Study of the Effect of Mechanical Activation on the Magnetic Properties of PbFe 0.5 Nb 0.5 O 3

Mossbauer studies of PbFe0.5Nb0.5O3 samples prepared by mechanical activation of PbO, Fe2O3 and Nb2O5 mixture and subsequent sintering at various temperatures T S were performed. The room temperature Mossbauer spectra consist of two doublets (D1 and D2) for the samples with T S 800 °C. The parameters of the doublet D1 correspond to Fe3+ in the octahedron environment. Doublet D2 has a lower isomer shift corresponding to Fe3+ with the coordination number 5 that indicates the presence of oxygen vacancies. Dependence of the temperature T N of magnetic phase transition on T S has a maximum at T S ≈ 700 °C. The effect of Fe3+/Nb5+ ordering degree and oxygen deficiency on T N is discussed.