Thermopower of La1−xCaxMn1−yFeyO3 as a result of asymmetric density of states

Thermopower, S, of La1−xCaxMn1−yFeyO3 with x=0.3 and y=0–0.09 is investigated between 25 and 310 K in magnetic fields B=0–10 T. Temperature dependence of S has a maximum in vicinity of the magnetic transition temperature, TC, exhibiting high sensitivity to y and to applied magnetic field. Detailed analysis of the experimental data shows that the temperature dependence of S in the paramagnetic insulating phase above TC is determined by asymmetry of the complex gap in the density of states around the Fermi level.