| Popis: |
In this article we report the results of electrical resistivity, thermopower and ac magnetic susceptibility measurements on Nd1-xSrxMnO3 with x = 0.40, 0.33 and 0.30. The room temperature paramagnetic to low temperature ferromagnetic transition temperature TC and electrical resistivity ?(T) are observed to depend on the processing conditions. ?(T) exhibits a shoulder at TC and a peak below TC. The latter peak is likely to be of intrinsic origin rather than due to lattice defects/ grain boundaries, etc. The resistivity decreases with increasing x as well as upon Ar annealing. Upon Ar annealing the thermopower [S(T)] below TC shows no appreciable change in magnitude, while above TC \S\ decreases. S(T) exhibits considerable differences between x = 0.33 and x = 0.3, which we attribute to a dopant induced insulator-metal (I-M) transition. Our thermopower data along with the resistivity and magnetic measurements show that the changes in the observed features in the ?(T) and S(T) cannot be related to magnetic ordering alone but the electronic transitions also have to be taken into consideration. ? 1999 American Institute of Physics. |
