Thermoelectric power and electrical conductivity of cadmium-substituted manganese ferrites

Thermoelectric power and electrical conductivity of cadmium-substituted man ganese ferrites were studied as a function of composition and temperature. On the basis of the sign of the Seebeck coefficient, the ferrites under inv estigation are classified as n-type semiconductors. The electrical conducti on in these ferrites is explained on the basis of the hopping mechanism. Pl ots of log(sigma T) versus 10(3)/T are linear and show a transition near th e Curie temperature. The activation energy in the ferrimagnetic region is i n general less than that in the paramagnetic region. The values of the char ge carrier mobility have been computed from the values of the electrical co nductivity and charge carrier concentration, and also discussed as a functi on of composition. The properties of cadmium-substituted manganese ferrites have been correlated with those of zinc-substituted manganese ferrites, ca dmium and zinc being two non-magnetic divalent ions occupying essentially t etrahedral A sites when substituted in ferrites. (C) 2000 Elsevier Science B.V. All rights reserved.