Temperature and doping dependence of the thermopower in LaMnO3

The temperature dependence of the thermopower (S) for La(1-x)A(x)MnO(3) (A = Sr, Pa, Pb, and Ca) perovs kites has been investigated systematically as a function of doping (x) in order to determine the role of several scattering mechanisms in the ferromagnetic phase. Irrespective of the nature of A ions, the thermopower shows strong temperature dependence and can be positive or negative depending on the doping level and temperature. In the ferromagnetic regime, thermopower follows an expression of the form S-0 + S3/2T3/2 + S4T4 over a wide range of temperature and doping. The coefficients S-0,S-3/2, and S-4 show systematic variation with the doping concentration. The large peak well below the ferromagnetic transition (T-c) and the complicated temperature dependence of S may be understood on the basis of electron-magnon scattering as predicted for an itinerant ferromagnet.