57Fe-enriched perovskites M(Fe0.5Nb0.5)O3 (M – Pb, Ba) studied by Mössbauer spectroscopy, NMR and XRD in the wide temperature range 4.2–533 K


The ⁵⁷Fe enriched perovskites Pb(Fe0.5Nb0.5)O3 and Ba(Fe0.5Nb0.5)O3 prepared by a ceramic method were studied by Mössbauer spectroscopy, NMR, conventional and synchrotron XRD. The temperature dependences of hyperfine and structural parameters from 4.2 K to temperatures above the ferroelectric ordering shows the presence of AF magnetic ordering transitions and the spin-glass transition under the Néel temperatures. In PFN sample, the structural change from trigonal to cubic structure around TN is observed, while the cubic structure is stable in the temperature range from 4.2 K to 530 K for BFN. The Fe/Nb perturbed arrangement was suggested based on results of Mössbauer and NMR spectroscopies.