Structural, magnetic, electrical and dielectric properties of MnxNi1-xFe2O4 spinel nanoferrites prepared by PEG assisted hydrothermal method

MnxNi1-xFe2O4 (x=0.2, 0.4, 0.6) nanoparticles were synthesized by a polyethylene glycol (PEG)-assisted hydrothermal route. We present a systematic investigation on the structural, magnetic, electrical and dielectric properties of the products by using XRD, FT-IR, SEM, TGA, VSM and dielectric spectroscopy, respectively. Single phased cubic spinel structure was confirmed for all samples and the average crystallite size of the products was estimated using Line profile fitting and ranges between 6.5 and 11 nm. The nanoparticles have ferromagnetic nature with small coercivity. The samples showed semiconducting behavior which is revealed from temperature dependent conductivity measurements. Temperature and frequency dependent dielectric property; dielectric permittivity (epsilon) and ac conductivity (sigma(AC)) studies for the samples indicated that the dielectric dispersion curve for all samples showed usual dielectric dispersion confirming the thermally activated relaxation typical for Debye-like relaxation referring to it as the Maxwell-Wagner relaxation for the interfacial polarization of homogeneous double structure. The particle size, saturation magnetization, coercive field, conductivity and dielectric constant of the samples are strictly temperature dependent and increased with Mn concentration. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.