Preparation of nanocrystalline MnFe2O4 by doping with Ti4+ ions using solid-state reaction route

Nanostructured manganese ferrites (MnFe2O4) with diameters in the range of 45-30 nm were synthesized by Ti4+ ion doping, using conventional solid-state reaction route. The substitution of Ti4+ ions created vacancies at Mn 21 sites and the coupling of ferrimagnetically active oxygen polyhedra was broken. This created nanoscale regions of ferrites. A reduction of magnetization for decreasing particle size was observed. Coercivity showed an increasing trend. This was explained as arising due to multidomain/ monodomain magnetic behaviour of magnetic nanoparticles. DC resistivities of the doped specimens indicated the presence of an interfacial amorphous phase formed by the nanoparticles. Zero-field cooled and field-cooled curves from 30 nm sized particles showed a peak at T-B (similar to 125 K), typical of superparamagnetic blocking temperature. (c) 2006 Elsevier B.V. All rights reserved.