Evidence for polaron conduction in nanostructured manganese ferrite

• Published in: Journal of physics. D, Applied physics Vol. 41; no. 18; pp. 185005 - 185005 (9)
• Main Authors: Veena Gopalan, E, Malini, K A, Saravanan, S, Sakthi Kumar, D, Yoshida, Yasuhiko, Anantharaman, M R
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 21.09.2008; Institute of Physics
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dielectric loss and relaxation; Dielectric properties of solids and liquids; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport in multilayers, nanoscale materials and structures; Exact sciences and technology; Permittivity (dielectric function); Physics; Dielectric dispersion; Iron Manganese Oxides Mixed; Electrical conductivity; Tunnel effect; Nanostructures; Hopping conduction; Dielectric relaxation; Ferrites; Nanoparticles; Phenomenological model; Dielectric losses; Permittivity; Activation energy; Power law; Coprecipitation; Polarons
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/41/18/185005

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