Magnetoresistance Plateau in La_(2/3)Ca_(1/3)Bi_xMn_(1-x)O_3 Granular System

The effect of doping additional Bi on the magnetoresistance (MR) of La2/3Ca1/3BxMn1-x O3 was investigated. It is found that traditional colossal magnetoresistance (CMR) peak can only be observed in the x0.05 samples and the peak value decreases with the increase of x, but the x≥0.05 samples show a magnetoresistance plateau above 200 K because of the presence of additional (La,Ca,Bi)-O layers. Moreover, this MR plateau is enhanced for the segregation of the La, Ca, and Bi elements.