Lattice effects of doping the Mn sites in La_(0.5)Ca_(0.5)MnO_(3)

摘要

The structure, magnetic, and transport properties of La_(0.5)Ca_(0.5)Mn_(1-x)M_(x)O_(3) (0≤x≤0.1) with M=Ge and Sn have been investigated systematically. A significant lattice expansion is observed in the Sn-doped samples, but not in the Ge-doped ones. At the same time, a substitution of Mn by Ge has little effect on Curie temperature (T_(C)), but increases the metal-insulator transition temperature (T_(P)). In contrast, the T_(C) decreases sharply for Sn doping, while the T_(P) shows an increase for x0.02. Compared with Ge doping, Sn doping is more effective in destroying the charge-ordered state. The difference in local lattice distortions due to the Ge and Sn doping is believed to be responsible for the present observations.