Competing magnetic interactions, low and high temperature magnetic properties of 0.3NiFe<inf>2</inf>O<inf>4</inf>–0.7Na<inf>0.5</inf>Bi<inf>0.5</inf>TiO<inf>3</inf> nanocomposites

We report on temperature dependent magnetization and anisotropy properties, magnetic interactions at low temperatures, high temperature magnetic properties and frequency dependent dielectric properties of 0.3NiFe2O4–0.7Na0.5Bi0.5TiO3 nanocomposites. X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) techniques are employed to study the crystal structure, morphology and the chemical state of the NiFe2O4 (NFO) nanoparticles, Na0.5Bi0.5TiO3 (NBTO) nanorods and nanocomposites. XRD and Raman spectroscopy studies indicate the formation of NFO, NBTO and the nanocomposites in pure phase. SEM and TEM images indicates the presence of both nanoparticles (from NFO) and nanorods (from NBTO) in the 0.3NiFe2O4–0.7Na0.5Bi0.5TiO3 nanocomposites and the lattice planes with respect to both the phases are confirmed from the selected area diffraction pattern. Magnetization measurements at various temperatures (300 K, 40 K, 10 K and 2 K), field cooled (FC) and zero field cooled (ZFC) magnetization from 300 K to 2 K are measured for the nanocomposites. Saturation magnetization value at 300 K and 2 K for the nanocomposites is seen to be 14.62 emu/g and 16.80 emu/g respectively. Existence of spin glass behavior and competing magnetic interactions in the 0.3NiFe2O4–0.7Na0.5Bi0.5TiO3 nanocomposites is confirmed from the ZFC and FC magnetization studies. Curie temperature value for 0.3NiFe2O4–0.7Na0.5Bi0.5TiO3 nanocomposites is observed to be 900 K. Frequency dependent dielectric studies shows the relaxation behavior of the nanocomposites with two relaxation times of 5.803 × 10−2 s and 2.770 × 10−4 s arising from NFO and NBTO phases.