Crystallite size induced crossover from paramagnetism to superparamagnetism in zinc ferrite nanoparticles.

Present work investigates the crossover from paramagnetism to superparamagnetism as a function of crystallite size in zinc ferrite nanoparticles using near edge X-ray absorption spectroscopy. Synthesized paramagnetic and superparamagnetic nanoparticles exhibit presence of Fe 2+ and Fe 3+ ions with dominant concentration of Fe 3+ ions. Fe L - and O K -edges spectra of paramagnetic nanoparticles consist of more intense spectral features compared to that of superparamagnetic nanoparticles. This reflects enhanced t 2 g and e g symmetry states of Fe–O hybridized states in paramagnetic nanoparticles induced by increased degree of crystallization. [ABSTRACT FROM AUTHOR]