Onset of size independent cationic exchange in nano-sized CoFe2O4 induced by electronic excitation

Abstract

Present work investigates electronic excitation induced cationic exchange phenomena in nano-sized cobalt ferrites using Mossabaur and X-ray absorption spectroscopies. The electronic excitations were produced by irradiation of 100 MeV O+7 at different fluences ranging from 1 x 10(11) to 1 x 10(14) ions/cm(2). Cubic spinel phase of cobalt ferrite remains preserved after irradiation. However, attributes of crystalline disorder were observed in irradiated materials. Crystallite size remain almost same for pristine and irradiated materials. X-ray absorption fine structure measurements show the preservation of valence state and spin state of metal ions under intense electronic excitation. These measurements also envisage bond breaking process induced by the electronic excitation. Mossbauer spectroscopic measurements also corroborate with the fine structure measurements that the valence state of Fe remains same after irradiation. Paramagnetic doublet which presents in the Mossabaur spectrum of pristine material disappears after irradiation, showing the evolution of irradiation induced magnetic ordering. Fe3+ ion increases with irradiation at octahedral site of spinel lattice. Magnetization of the material slightly increases after irradiation at the fluence of 5 x 10(13) and 1 x 10(14) ions/cm(2). (C) 2015 Elsevier B.V. All rights reserved.