Substituting effects of Sm in polycrystalline La-Ca-Mn-O

The Sm substituting effects for La in Lao(0.67)Ca(0.33)MnO(3) have been stu died systematically. With increasing Sm doping amount, the metal-isolator p hase transition temperature for the samples decreases monotonically, the co rresponding peak resistivity increases dramatically and the Curie temperatu re decreases monotonically. The substitution of La-Ca-Mn-O with 0.13% Sm fo r La improved the magnetoresistance ratio by an order of magnitude. The eff ects of doping with Sm can be explained in terms of the lattice effects. An irreversible MR behaviour was observed in the Sm-doped compound. This effe ct was enhanced with increasing Sm doping amount.