Structural, dielectric and ferromagnetic behavior of (Zn, Co) co-doped SnO2 nanoparticles

Abstract

Nanoparticles of basic composition Sn0.94Zn0.05Co0.01O2, Sn0.92Zn0.05Co0.03O2 and Sn0.90Zn0.05Co0.05O2 were synthesized by chemical precipitation method. The incorporation of Co and Zn in SnO2 lattice introduced significant changes in the physical properties of all the three nanocrystals. The average particle size estimated from TEM data decreased from 15.71 to 6.41 nm with enhancement in concentration of oxygen vacancies as Co content is increased from 1 to 5wt%. Increasing Co content enhanced the Sn:O atomic ratio as a result concentration of oxygen vacancies increased. The dielectric study revealed strong doping dependence. The dielectric parameters (ε′, tanδ and σac) increased with increasing Co content and attained maximum values for 5% (Zn, Co) co-doped SnO2 nanoparticles. The dielectric loss (ε′′) exhibited dispersion behavior and the Debye’s relaxation peaks observed in dielectric loss factor (tanδ), whose intensities increased with increasing Co content. The variation of dielectric properties and ac conductivity revealed that the dispersion is due to Maxwell-Wagner interfacial polarization and hopping of charge carriers between Sn+2/Sn+3 and Co+2/Co+3. The large dielectric constant of all samples made them interesting materials for device application. Magnetization measurements (M (H) loops) revealed enhancement in saturation magnetization with doping which is due to the formation of large amount of induced defects and oxygen vacancies in the samples. The present study clearly reveals doping dependent properties and the oxygen vacancies induced ferromagnetism in Zn, Co co-doped SnO2 nanoparticles having applications in ultra-high dielectric materials, high frequency devices and spintronics.