The study of magnetic ordering in the spinel system Zn xNi 1− xFeCrO 4 by neutron diffraction

Abstract

Neutron diffraction measurements have been performed in the temperature range 600 K⩾ T ⩾10 K on the spinel system Zn x Ni 1− x FeCrO 4 ( x=0.2, 0.4, 0.6 and 0.8) synthesized in the ceramic sintering method. The moment distributions in the two sublattices and their ordering as affected by compositional change and temperature variation have been determined. Ferrimagnetic transition temperatures and spin compensation temperatures for all the specimens have been determined. The system shows significant deviations from the usual ferrimagnetic behavior, which increases with the increase of diamagnetic substitutions, being more prominent in the B sublattice. The ferrimagnetic ordering is perturbed due to the presence of non-collinear spins mainly in the B site. Presence of small fluctuating magnetic clusters for x⩾0.6 is evident from the diffuse nature of the scattered intensity. A qualitative explanation of the observed features is put forward in the light of competing inter and intra sublattice exchange interactions. A randomly canted ferrimagnetic ordering is suggestive for the system at x⩽0.4, while a semi-spin glass like transition is favorable for x⩾0.6 due to large reduction in moment and evolution of diffuse signal from short-range clusters at low temperatures.