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 transition at lower temperature appears for Cu-doped samples. The new transition moves toward low temperature with increasing of Cu content. A new conductive proceeding related to Cu ion may exist. Magnetoresistance at liquid nitrogen shows that MR increased three orders when x is changed from 0 to 0.15. Moreover, the main variation of magnetoresistance is below the field of 1 T.