Properties of MgFe2O4 Nanocrystallites to Bulk

In this work, nanocrystalline MgFe2O4 powders were synthesized by co-precipitation method and then
heat treated at different temperatures in the range from 200 - 1400°C with the objective of obtaining
superparamagnetic properties. The single phase cubic structure of MgFe2O4 with space group Fd3m
was confirmed by powder X-ray diffraction (XRD), and the average crystallite size of each sample has
been estimated from the (311) peak of the XRD spectra using the Debye-Scherrer equation.
Formation of ferrites has also been studied by using FTIR. On heating, the crystallite size increased
with corresponding increase in saturation magnetization (Ms), and for 1400°C, it is 27.96 emu/g that is
close to the bulk MgFe2O4. On increasing the crystallite size, the coercivity (Hc) increased passed
through a maximum and then dropped, indicates a transition from single to multi-domain state at a
critical particle size ~52.5 nm. B-H loop measurements have been carried out by B-H loop tracer. The
room temperature Mössbauer spectra of the samples show six-figure patterns for higher crystallite
size and a doublet pattern for smaller crystallite size, which is confirmed the appearance of
superparamagnetic (SPM) relaxation of the nanoparticles with crystallite size up to 7.7 nm in the
samples. Curie temperatures have been determined from the temperature dependence of
permeability. Curie temperatures for the samples of this composition do not vary significantly with the
variation of sintering temperatures. From the Raman spectrum all the peaks observed in samples
matched with Raman active modes of MgFe2O4 spinel structure. The optimized properties make these
nanoparticles a potential candidate for various applications including biomedical field.