Superparamagnetic zinc ferrite: A correlation between high magnetizations and nanoparticle sizes as a function of reaction time via hydrothermal process

Abstract

Superparamagnetic zinc ferrite nanoparticles with high magnetization were successfully synthesized by hydrothermal method at 110 degrees C under different reaction times from 2 to 24 h. Elemental analysis of the nano particles determined by inductively coupled plasma atomic emission spectroscopy and energy dispersive X-ray spectrometer results proved that the samples are zinc ferrite. X-ray diffraction (XRD) and Fourier transmission infrared spectroscopy analysis displayed that zinc ferrite nanoparticles were single phase of cubic ferrite. The particles size, d(XRD) of the nanoparticles calculated from XRD patterns increased as the reaction time increased. From the images of transmission electron microscopy (TEM), the particle sizes, d(TEM) were also calculated and increased from 6.8 +/- 2.5 to 10.6 +/- 5.1 nm as the reaction time increased, which were consistent with the d(XRD) Magnetic measurements revealed that the magnetization curves of the synthesized nanoparticles show super paramagnetic behavior with zero coercivity and remanence. And, the magnetization values also increased to a maximum value of 30.8 emu/g (measured at 20 kOe) as the particle size increased to similar to 10 nm with the increase of reaction time. At this particle size limit, this is a considerable high value compared to the superparamagnetic zinc ferrite nanoparticles studies. Magnetization values were also extrapolated. It is seen that to a certain degree, the average particle sizes of the products and hence high maximum magnetization can be tuned by simply adjusting the parameter, reaction time by hydrothermal process.