Giant magnetocapacitance in magnetoelectric BNT/NFO particulate composites

Bi0.5Na0.5TiO3 (BNT) and NiFe2O4 (NFO) ceramics were synthesized using the sol–gel method. Further, a series of (1−x)BNT–xNFO (x = 0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.25, 0.30, 1) magnetoelectric (ME) composites were prepared by microwave sintering. The composites phase purity and microstructure were investigated through X-ray diffraction and scanning electron microscope. The highest value of leakage current density was observed for 0.70BNT–0.30NFO, i.e., 3.77 × 10–5 A/cm2 at 5 kV/cm. Pure BNT showed higher dielectric constant (i.e., 576 at 1 kHz) at room temperature, which further decreases with NFO content. All composites showed ferromagnetic behavior. The direct and indirect ME coupling was examined by change in capacitance in an applied magnetic field. Giant magnetocapacitance was observed for 0.70BNT–0.30NFO, i.e., 27.51% at 1 kHz frequency. The quadratic–linear nature and higher-order ME coupling of composite samples have been computed using the Landau theory.