Room temperature magnetodielectric effect in composites of cobalt containing silica based nanoglass and mesoporous alumina

Abstract

Silica based nano-glass of composition 30CoO-70SiO2 was formed within mesoporous alumina (MA) by Sol-gel protocol. Small angle x-ray scattering (SAXS) and TEM studies reveal theordered structure of MA. Small polaron hopping between Co2+ and Co3+ species was the cause of electrical conductivity of the nanocomposite (NC) system. The resistivity and activation energy values of NCwerefound to be low and followed Mott’s small polaron hopping model. The irreversibility of ZFC-FC curve and satisfactory fit with Almeida-Thouless (AT) relation confirmed the spin-glass nature of the sample. The hysteresis in M-H data showed the ferromagnetic nature of the sample. Enhanced magnetodielectric (MD) effect (17.3-2.6) % at frequency 200 KHz-2 MHz with very low dissipation factor (0.02-0.07) found in this system were explained on the basis of Catalan’s model of two dielectricshaving different resistivity values connected in series. These materials will be suitable for fabricating magnetic sensors and magnetic supercapacitors.