Study of the cation distribution and crystallographic properties of the spinel system NiCrxFe2-xO4 (0.0≤x≤1.0) by neutron diffraction

- NiCrxFe2−xO4 ferrites crystallize at 1350 °C and possess cubic symmetry.
- Cation distribution and crystallographic parameters have been determined precisely.
- Cell parameter decreases with increasing Cr content in the system.
- Ferrimagnetic ordering was found at room temperature for the samples with x ≤ 0.8.

The spinel system NiCrxFe2-xO4 with composition x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 were obtained by solid state sintering technique in air at 1350 °C. X-ray and neutron powder diffraction experiments have been performed on the samples at room temperature to characterize the materials. The formation of the single phase cubic spinel structure has been confirmed by the sharp peaks of X-ray diffraction patterns for all the samples. Rietveld refinement of the neutron diffraction data showed cubic symmetry corresponding to the space group F d3-m. The distributions of cations over the two sublattices and other crystallographic parameters have been determined precisely from the analysis of the neutron diffraction data. The cell parameter decreases with increasing Cr content in the system. The tetrahedral and octahedral bond distances have been calculated from the analysis of the neutron diffraction data. Sublattices and net magnetic moments were deduced from the refinement of neutron diffraction data. The magnetic structure at room temperature was found to be ferrimagnetic for the samples x ≤ 0.8 with no remarkable magnetic moments at x = 1.0.