Structural, magnetic, and transport properties in La(2+4x)/3Sr(1−4x)/3Mn1−xCuxO3 (0⩽x⩽0.20) system

A series of the double-doping samples La(2+4x)/3Sr(1−4x)/3Mn1−xCuxO3(0⩽x⩽0.2) with the Mn3+/Mn4+ ratio fixed at 2:1 have been prepared. The structural, magnetic, transport properties and magnetoresistance of the series samples have been investigated. It is found that no apparent crystal structure change is introduced by Cu doping up to x=0.20. But the Curie temperature TC and magnetization M are strongly affected by Cu substitution. A remarkable magnetotransport behavior, characterized by double bumps, is observed, and an obvious low-temperature upturn is found in the range of 0.07⩽x⩽0.12. As a result, the temperature range of colossal magnetoresistance (CMR) is greatly broadened. Moreover, it is found that the room temperature magnetoresistance (MR) of double-doping samples is obviously larger that the undoped La2/3Sr1/3Mn1−xCuxO3 at 300 K, which can give a guide for the adequate selection of the room temperature CMR materials.