Magnetic properties of La-substituted NiFe2O4 via egg-white precursor route

Nano-sized NiFe2-xLaxO4 ferrites (x = 0.00, 0.01, 0.02, 0.03, 0.04, 0.5, 0.07 and 0.09) were synthesized for the first time by using metal nitrate and egg-white extract in aqueous medium. The ferrites were characterized by DTA-TG, XRD, TEM, FT-IR and VSM techniques. The thermal decomposition behavior revealed that the precursors were completely decomposed at about 420 degrees C. TEM image shows agglomerated nanoparticles with crystallite sizes agrees well with that estimated by XRD measurement. XRD patterns show a secondary phase of LaFeO3 besides the cubic structure of the La-substituted ferrites. The lattice parameters, X-ray density and crystallite size were found to increase with the increasing La content. The VSM measurement exhibited a ferromagnetic property for all the samples at room temperature. With increasing La, M-s was found to decrease while H-c increased. The decrease in the saturation magnetization is attributed to the paramagnetic properties of lanthanum, which prefer to substitute iron present in the octahedral sites. The increase in the coercivity is due to either the stronger magnetocrystalline anisotropy induced by La substitution or the change in the crystallite size. (c) 2011 Elsevier B.V. All rights reserved.