CU DOPING EFFECT ON MN SITES OF LA2 3CA1/3 MNO3 SYSTEM/

The temperature dependence of resistance and magnetoresistance at 77 K for Cu-doped La2/3Ca1/3Mn1-xCuxO3 have been investigated. Besides the transition similar to the Cu-free sample at similar to 260 K, a new t ransition at lower temperature appears for Cu-doped samples. The new t ransition moves toward low temperature with increasing of Cu content. A new conductive proceeding related to Cu ion may exist. Magnetoresist ance at liquid nitrogen shows that MR increased three orders when x is changed from 0 to 0.15. Moreover, the main variation of magnetoresist ance is below the field of 1 T.