Ba(Fe_0.5Nb_0.5)O₃ studied by Moessbauer spectroscopy and SQUID magnetometry

The ceramic multiferroic barium iron niobate BaFe_0.5Nb_0.5O₃ (BFN) studied in this work belongs to the single-phase perovskites exhibiting high value of dielectric permittivity [1]. The aim of our study was to clarify the transition temperature to magnetically ordered state from the temperature dependence of the hyperfine parameters and magnetic measurements. The sample was prepared by the solid-state method. Scanning Electron Microscopy/Energy Dispersive Spectrometry (SEM/EDS) and X-ray fluorescence analysis (XRF) and X-ray diffraction (XRD) were employed for sample characterisation and check of the element and phase composition. The Moessbauer measurements were carried out in the temperature range 4.2-300 K with the in-field spectrum taken in external field of 6 T at 4.2 K. Magnetic ordering transition was found in a relatively wide range of temperatures around 25 K.The in-field spectra indicate antiferromagnetic ordering. ZFC and FC susceptibilities were measured by a SQUID magnetometer. The onset of the antiferromagnet phase is at about 28 K. (authors)