This ferrite was studied by using Mössbauer spectroscopy, X-ray diffraction and vibrating-sample magnetometry. The crystal structure was that of a spinel, and the lattice constants obeyed Vegard's law. The Mössbauer spectra consisted of two 6-line patterns which corresponded to Fe3+ at the tetrahedral (A) and octahedral (B) sites. The Curie temperature decreased linearly with Cr concentration, thus suggesting that the super-exchange interaction Fe(A)-O-Fe(B) link was stronger than that of the Fe(A)-O-Cr(B) link. The Debye temperatures for the A- and B-sites of Fe1.9Cr0.1MgO4 were found to be 515 and 265K, respectively. Atomic migration in Fe1.9Cr0.1MgO4 began near to 350K and increased rapidly, with increasing temperature, so that 50% of the ferric ions at the A-sites had moved to B-sites by 600K.

Atomic Migration in Mg(Fe,Cr)2O4. S.W.Lee, S.Y.An, G.Y.Ahn, C.S.Kim: Journal of Applied Physics, 2000, 87[9], 6238-40