Frequency and temperature dependent intrinsic electric properties of manganese doped cobalt ferrite nanoparticles

Abstract

This paper reports a series of investigations on the frequency and temperature dependent intrinsic electric properties of manganese doped cobalt ferrite nanoparticles. The investigated samples were prepared via solid state reaction route using the planetary ball milling technique. The XRD patterns confirm their crystallinity and single phase spinel structure. The Field Emission Electron Scanning Microscopic (FE-SEM) micrographs show the agglomerated particle with a nearly spherical shape. The estimated lattice constant is found to decrease but the crystallites size to increase with the Mn content. The ac resistivity is found to decrease exponentially with the increase of frequency due to the effect of multilayer capacitance. Conversely, the ac conductivity is observed to increase exponentially with the frequency due to increased hopping between metallic cationsFe2+and Fe3+. The temperature dependent ac resistivity exhibits the semiconducting behavior of the materials above room temperature. The variation in both the resistivity and conductivity is assumed to follow the Arrhenius equation at a selected frequency of 10 kHz. The estimated activation energy using the Arrhenius equation of ac conductivity in the ferro region is found to increase with the Mn content. This increasing trend in activation energy signifies ferrimagnetic-to-paramagnetic phase transition. Besides, the electric modulus shows the contributions of both the grain and grain boundaries to the conduction mechanism in the materials. This nature of temperature dependent resistivity is as usual for the majority of nanoferrite materials. Keywords: AC resistivity, AC conductivity, Electric modulus, Activation energy