Crystallographic and magnetic properties in CoFe2-xCrxO4

Co-Cr ferrite has been studied with Mossbauer spectroscopy, X-ray diffracti on, and vibrating sample magnetometery (VSM). The crystal structure for thi s system is a spinel structure, and the lattice constants are in accordance with Vegard's law. The Mossbauer spectra consist of two six-line patterns corresponding to Fe3+ at the tetrahedral (A) and the octahedral (B) sites. The Neel temperature decreases linearly with Cr concentration, suggesting t he superexchange interaction Co-O-Fe link is stronger than that for the Cr- O-Fe link. The Debye temperatures for the A and the B sites of CoFe1.9Cr0.1 O4 are found to be theta(A)=827+/-5 K and theta(B)=218+/-5 K. Atomic migrat ion of CoFe1.9Cr0.1O4 starts near 295 K and increases rapidly with increasi ng temperature to such a degree that 64 % of the ferric ions at the A sites have moved over to the B sites at 600 K. The VSM data showed that the satu ration magnetization decreased with increasing quantity of Cr ions.