Evidence for polaron conduction in nanostructured manganese ferrite

Nanoparticles of manganese ferrite were prepared by the chemical co-precipitation technique. dielectric parameters, namely, real and imaginary dielectric permittivity (ε and ε), conductivity (σac) and dielectric loss tangent (tan δ), were measured in the frequency range 100 kHz–8MHz at different temperatures. The variations of dielectric dispersion (ε) and absorption (ε) with frequency and temperature were also investigated. The variation dielectric permittivity with frequency and temperature followed the Maxwell–Wagner based on interfacial polarization in consonance with Koops phenomenological theory. dielectric loss tangent and hence ε exhibited a relaxation at certain frequencies and at higher temperatures. The dispersion of dielectric permittivity and broadening of the absorption suggest the possibility of a distribution of relaxation time and the of multiple equilibrium states in manganese ferrite. The activation energy estimated the dielectric relaxation is found to be high and is characteristic of polaron conduction in nanosized manganese ferrite. The ac conductivity followed a power law dependenceσac = Bωn typical of charge transport assisted by a hopping or tunnelling process. The minimum in the temperature dependence of the frequency exponent n strongly that tunnelling of the large polarons is the dominant transport process