Dielectric properties and signature of multi-ferroelectricity in Co2FeO4: A structurally single phased and bi-phased spinel oxide

Abstract

The ferrite Co2FeO4 has been stabilized in single phased and bi-phased cubic spinel structure depending on annealing temperature of as prepared sample. This ferrite showed many interesting dielectric properties. AC conductivity study showed semiconductor characters with activation energy in the range 0.46–1.02eV. The combination of small and correlated barrier hopping of polarons controlled AC conductivity mechanism in the samples. Cole–Cole plot of the complex impedance spectrum suggested dielectric contribution from grains and grain boundaries of the material and electrical modulus confirmed it. The present ferrite material shows sufficiently large dielectric constant (30–200) and remarkably low loss (0–0.35) in a wide range of temperature and frequency. The single phased sample has shown lowest conductivity and dielectric loss. Maxwell–Wagner type interfacial polarization affected the dielectric properties at lower frequencies. A broad bump/peak in the temperature dependence of dielectric constant curves signalled the multi-ferroelectric nature of the material. Room temperature ferroelectric loop is, indeed, good in some of the samples and magnetic field controlled ferromagnetic blocking has been tailored in a wide temperature range 80–400K.