Magnetization enhancement in nanostructured random type $MgFe2O4$ spinel prepared by soft mechanochemical route

In this paper we report results of structural, spectroscopic, and magnetic investigations of $MgFe2O4$ nanoparticles prepared by soft mechanochemical synthesis. $MgFe2O4$ nanoparticles crystallize in $Fd3¯m$ space group with mixed cation distribution and reduced percentage of $Fe3+$ at tetrahedral (8a) sites. Discrepancy in the cation distribution compared to that in the bulk Mg–ferrite is one of the highest known. X-ray line broadening analysis reveals crystallite size and strain anisotropy. The saturation magnetization, $Msat=62emu/g$ measured at 5 K is twice higher than that found in the bulk counterparts. Such high value of $Msat$ is attributed to the low value of cation inversion parameter $(δ=0.69)$⁠, to the core/shell structure of the nanoparticles and to the surface/volume ratio. Mössbauer spectrum collected at room temperature reveals ferrimagnetic ordering between $Fe3+$ ions in $8a$ and $16d$ sites, while zero-field-cooled (ZFC) and field-cooled (FC) M(T) measurements were shown superparamagnetic state above 350 K.