Critical change of magnetoresistance with bandwidth and doping in perovskite manganites

To explore the optimized colossal magnetoresistance (MR), i.e., higher MR with lower field, magnetotransport properties of single-crystalline perovskite manganites have systematically been investigated. Near x=1/2 with intrinsic instability of charge ordering (a 1/1 ordering of Mn3+/Mn4+), the one-electron bandwidth (W) is varied by reducing the radius of R-site cation in R1-xSrxMnO3. For R=Nd, the MR behavior is rather canonical, while for R=Sm, the field-induced nonmetal-to-metal transition of the first order shows up accompanying a change in resistivity by several orders of magnitude as a result of an enhanced antiferromagnetic interaction. copyright 1997 American Institute of Physics