NiFe2O4 - ZnO semiconducting nanocomposites: Studies of room temperature magnetoelectric coupling and electronic transport

Abstract

Nanocomposites of xNiFe2O4 – (1-x)ZnO (x = 0.2, 0.3 and 0.5) have been prepared through chemical “pyrophoric reaction process”. Structural characterizations confirm the formation of both NiFe2O4 and ZnO phases in nanocomposites. The room temperature magnetoelectric coupling, dielectric and temperature dependence of electrical properties of the prepared nanocomposites have been investigated. The observed magnetoelectric coupling may be owed to the field dependent magnetostriction property of the piezomagnetic phase of the nanocomposites. The magnetoelectric voltage is measured in both transverse and longitudinal directions. Electrical transport studies are carried out using an ac impedance spectroscopy and dc resistivity techniques. Metal-semiconductor transition of the nanocomposites has been explained on the light of delocalized and localized charge carrier. Detailed analysis of ac conductivity with frequency at varying temperature suggests the thermally activated electronic transport conduction mechanism for large and small polaronic hopping in the nanocomposites. The semiconducting band gap of the nanocomposites has also been estimated using recorded absorbance spectra. Light-dependent current-voltage characteristics are non-Ohmic in nature and exhibit significant electrical memory effect with resistive switching. On light illumination, there is a significant decrement in current with quenching of hysteresis loop suggesting high recombination of the photo-generated carriers.