Diamagnetism, transport, magnetothermoelectric power, and magnetothermal conductivity in electron-doped CaMn1-xVxO3 manganites

The effects of V doping on field-cooled magnetization M-FC(T), zero-field-cooled magnetization M-ZFC(T), resistivity rho, thermoelectric power S, and thermal conductivity kappa in manganites CaMn1-xVxO3 (0.02 <= x <= 0.08) have been investigated systematically. As the V doping level exceeds 0.02, an anomalous "diamagnetism" has been observed. It is suggested that the force generated by the orbit rotation of e(g) electron in Mn3+O6 octahedron makes the spin tilt, as a result, the vector sum of individual spins may be along or opposite to the direction of the applied magnetic field, and macroscopically, the average magnetization exhibits positive or negative values. In addition, the transport mechanism in the high and low temperature ranges is dominated by the small polaron conduction and the variable-range-hopping conduction, respectively, according to the fitting analysis of the temperature dependence of Seebeck coefficient S(T) and resistivity rho(T). Both S and kappa peaks appearing at low temperature is gradually suppressed by V doping. Additionally, obvious magnetothermoelectric power and magnetothermal conductivity are observed in the temperature region which an anomalous diamagnetism appears. The results are discussed based on spin-orbital coupling and spin-phonon coupling induced due to V doping, respectively. Moreover, the large thermoelectric figure of merit Z=S-2/rho kappa for the slightly V-doped sample suggests that the V-doped manganite may be a good candidate for thermoelectric materials. (c) 2006 American Institute of Physics.