Large magnetoresistance of heavily doped Nd1-xSrxMnO3 (0.55≤x≤0.75)

We have investigated heavily doped Nd1-xSrxMnO3 with 0.55 <= x <= 0.75 in detail. In 0.60 <= x <= 0.72, ferromagnetic correlation accompanying magnetoresistance (MR) is observed at low temperatures. The ferromagnetic correlation and the concomitant MR are most enhanced at x = 0.625 where the 3z(2) - r(2) and x(2) - y(2) orbital orders compete with each other in a bicritical manner. This strongly suggests that the orbital fluctuation arising from the competition gives rise to the ferromagnetic fluctuation closely linked to the MR. (C) 2007 Elsevier B.V. All rights reserved.