XRD, magnetic and Mossbauer spectral studies of nano size aluminum substituted cobalt ferrites (CoAlxFe2-xO4)

Aluminum substituted cobalt ferrites having particle size similar to 10 nm were prepared using aerosol route, which increases with annealing temperature. The unit cell parameter 'a' and saturation magnetization decreases linearly with the increase of aluminum concentration. This is due to the smaller ionic radius and the diamagnetic nature of the Al3+, respectively. Room temperature Mossbauer spectra of the samples annealed at 1200 degrees C show broad sextets, which were fitted with different sextets, indicating different local environment of both tetrahedrally and octahedrally coordinated iron cation. Further, hyperfine field of the samples decreases with the increase of Al3+ concentration due to the fact that the Al3+ diamagnetic species reduce the magnetic interactions. Cations distribution indicated a increase in Fe3+ (oct.)/Fe3+ (tet.) ratio on increasing the Al3+ concentration. (C) 2006 Elsevier B.V. All rights reserved.