Turkish Journal of Physics

Electrical Conductivity and Thermoelectric Power of Gd^{3+} Substituted Mg-Cd Ferrites




The temperature depondence of elctrical resistivity and thermoelectric power is measured in the temperature range 300 to 800 K for a series of Gd^{3+} substituted Mg-Cd ferrites. The resistivity increases with Gd^{3+} content. A break has been observed in the log \rho versus 10^{3}/T variation around Tc. The break is associated with a change of the activation energy around the Curie temperature. This is attributed to the change in magnetic ordering. The small polaron hopping mechanism is used to explain the conduction behaviour in ferrites. From the sign of the observed Seebeck coefficient, the Mg-Cd ferrite samples are found to exhibit n-type semiconducting behaviour. But the addition of Gd^{3+} changes the conductivity from n-type to p-type. The behaviour has been explained on the basis of the excess or deficiency of the iorn ions in the composition on Gd^{3+} substitution.

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