Mossbauer and magnetic studies of MFe2O4 (M=Co, Ni) nanoparticles

Nanocrystalline MFe2O4 (M=Co, Ni) particles are synthesized by citrate precursor technique. Mossbauer and magnetic studies are carried out with the CoFe2O4 samples having particle sizes of 9, 14 and 30 nm and the NiFe2O4 samples having particle sizes of 9, 21 and 30 nm. The intrinsic magnetic parameters are found to vary with the particle size. The magnetic interactions and cation distribution present in these systems influence the room temperature Mossbauer parameters. Ferrimagnetic sextets are observed for all the different particle sizes. The observed reduction of the magnetic hyperfine field values with the decrease in the size of MFe2O4 particles are attributed to the intrinsic size effect and the canted spin structure at the surface of the nanoparticles.