Mössbauer study of cobalt ferrite nanocrystals substituted with rare-earth Y3+ ions

Mössbauer spectroscopy is used to characterize the crystallite size and structure of CoFe2−xYxO4 (x=0, 0.1, 0.3, 0.5) ferrite nanocrystallites synthesized by the sol–gel auto-combustion method. The effect of the substitution of Fe3+ ions by Y3+ ions on the structure of cobalt ferrite nanocrystallites is investigated. The Mössbauer spectra showed two sets of six-line hyperfine patterns for all the samples, indicating the presence of Fe in both A and B-sites. On increasing the concentration of doped Y, the hyperfine field strength and the isomer shift first increase and then decrease, whereas the quadrupole splitting continuously increases. The superparamagnetism was observed for all the samples and the change of ratio of the superparamagnetism component reflects the size of crystal grain.