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-crystallin e perovskite manganites have systematically been investigated. Near x= 1/2 with intrinsic instability of charge ordering (a 1/1 ordering of M n3+/Mn4+), the one-electron bandwidth (W) is varied by reducing the ra dius or R-site cation in R1-xSrxMnO3. For R=Nd, the MR behavior is rat her canonical, while for R=Sm, the field-induced nonmetal-to-metal tra nsition of the first order shows up accompanying a change in resistivi ty by several orders of magnitude as a result of an enhanced antiferro magnetic interaction. (C) 1997 American Institute of Physics.