Temperature dependent electrical and magnetic properties of CoWO4 nanoparticles synthesized by sonochemical method

CoWO4 nanoparticles were synthesized by a facile sonochemical method. The formation of wolframite type monoclinic structure was studied by XRD. Both SEM and TEM analyses revealed nearly spherical morphology with the particle size in the range of 20-30 nm. The XPS studies confirmed the 2+ and 6+ oxidation states for the metal elements: Co and W, respectively. A maximum d.c. conductivity of 1.24 × 10−5 S cm−1 was obtained from a.c. impedance spectroscopy measurements at 640 °C. The conductance spectra inferred that the hopping of charge carriers is localized motion. The ZFC-FC magnetization curves predicted the antiferromagnetic transition temperature at 20 K. An enhancement in the magnetization observed below the Néel temperature supported the core-shell model of antiferromagnetic nanoparticles. Curie-Weiss fitting predicted the Curie temperature of −47.6 K and Curie constant of 7.2 K emu mol−1. A linear relationship obtained above the Néel temperature confirmed the existence of paramagnetic behavior in CoWO4 nanoparticles above the antiferromagnetic transition temperature.