A systematic study on the structural,magnetic,and electrical transport properties was performed for the LaMn1-xCuxO3 system.A single phase of orthorhombic perovskite structure was formed for x = 0.05-0.40.A striking paramagnetic-ferromagnetic transition and a considerable magnetoresistance effect were observed at the ferromagnetic ordering temperature TC,but no insulator-metal transition induced by Cu-doping was observed.Below TC,a visible unexpected drop was observed in the ac susceptibility and zero-field-cooled dc magnetization for the dilute doped samples with x ≤ 0.10,which was proven to be associated with domain wall pinning effects by milling the bulk material into single domain particles.It is validated that there is no exchange interaction between Cu and Mn,and double exchange interactions between Mn3+ and Mn4+ are induced by Cu-doping in the anti-ferromagnetic LaMnO3 matrix,whereas the severe distortion and disorder caused by occupied-dopant prohibits charge carriers from hopping.
