Study of structural, dielectric, electric, magnetic and magnetoelectric properties of K0.5Na0.5NbO3− Ni0.2Co0.8Fe2O4 composites

Magnetoelectric composites with general formula (x) Ni0.2Co0.8Fe2O4- (1- x) (K0.5Na0.5)NbO3 (x = 0, 0.10, 0.20, 0.30, 0.40, 0.50 and 1.0) have been synthesized by solid state reaction method. X-ray diffraction pattern asserts the existence of both the constituent phases in the synthesized composites. FESEM micrographs are used to investigate the microstructure and for calculation of average grain size of the composites. Temperature dependent dielectric properties are investigated as a function of temperature and found to enhance with addition of ferrite in the composites. P-E hysteresis loops obtained for individual (K0.5Na0.5)NbO3 (KNN) phase and composites indicate the ferroelectric ordering in the composites. Saturation and remnant magnetization show increasing trend with increase in NCFO concentration. FC-ZFC magnetization curves indicate charge ordering, metal-insulator transition (Verwey transition) in NCFO and composites. Impedance spectroscopy shows that bulk resistance reduces with increase in temperature, thereby indicating negative temperature coefficient of resistance (NTCR) behaviour of the composites. The magnetoelectric effect is confirmed by measuring magnetoelectric voltage coefficient, αME and the maximum value of αME is 5.389 mV/cm-Oe for 20% NCFO-80% KNN composite.