Temperature-dependent vibrational spectroscopic and X-ray diffraction investigation of nanosized nickel chromite.

The nanocrystalline nickel chromite ( NiCr 2 O 4 ) with particle size of ∼20 nm was prepared by auto-combustion method. The nanocrystals were characterized by powder X-ray diffraction, vibrational spectroscopy and magnetic measurements. The expected structural phase transitions (cubic–tetragonal–orthorhombic) were studied by methods of temperature-dependent X-ray powder diffraction and vibrational spectroscopy. The evolution of the Raman spectra and X-ray diffraction patterns collected from 350 K down to 4 K confirmed the cubic-to-tetragonal distortion at ∼250 K, whereas the tetragonal-to-orthorhombic transition was not confirmed in the nanocrystalline sample. [ABSTRACT FROM AUTHOR]