Cation distribution and magnetic properties in chromium-substituted nickel ferrites prepared using aerosol route

Cation distribution have been investigated using X-ray diffraction, magnetic and Moessbauer spectral studies in chromium-substituted nickel ferrites prepared by aerosol route. Cation distribution indicates that the chromium atom occupy octahedral site upto x=0.8, and then also enters into tetrahedral site. The saturation magnetization decreases linearly with the increase of chromium concentration due to the diamagnetic nature of the Cr3+. However, interesting behaviour is observed in the coercivity. Initially it increases slowly with the chromium concentration but when x>0.8 a very large increase has been observed. This was attributed to the specific cation distribution of Cr3+ which results an unquenched orbital angular momentum and a large anisotropy. Room temperature Moessbauer spectra of as obtained samples exhibited a broad doublet resolved into two doublets corresponding to the surface and internal region atoms. The samples annealed at 1200 deg. C show broad sextets, which were fitted with different sextets, indicating different local environment of both tetrahedral and octahedral coordinated iron cation. - Graphical abstract: Hysterisis loop of chromium-substituted nickel ferrites after annealing at 1200 deg. C