Structural and magnetic phase transition of sol–gel-synthesized Cr2O3 and MnCr2O4 nanoparticles

Abstract

Cr2O3 and MnCr2O4 spinel chromite nanoparticles were synthesized using chemically derived sol–gel technique. Crystal structure was analyzed using X-ray diffraction, and phase transition from a rhombohedral symmetry (R-3c) for Cr2O3 to a spinel cubic symmetry (Fd3 m) for MnCr2O4 has been observed. Data obtained from diffraction were also utilized to evaluate the lattice parameters, crystallite size and unit cell volume. Micrographs obtained using a field emission scanning electron microscope exhibited well-shaped, homogenously distributed 30–70-nm-sized nanoparticles, with well-defined grain. Stoichiometric composition of all the elements present in the samples was confirmed using energy-dispersive X-ray spectroscopy. Dynamic light scattering measurement was performed to corroborate the hydrodynamic diameter and distribution of Cr2O3 and MnCr2O4 nanoparticles. The magnetic behavior of samples was scrutinized as a function of temperature and applied field. It was observed that Cr2O3 exhibited paramagnetic behavior both at room temperature and at 5 K, while a magnetic phase transition from ferro to para was observed in MnCr2O4 with a Curie temperature, T c ~ 50 K.