EXTRINSIC GIANT MAGNETORESISTANCE IN CHROMIUM(IV) OXIDE, CRO2

Polycrystalline CrO2 is shown to exhibit a giant magnetoresistance (GM R) at low temperatures. A rapid decrease in the GMR with increasing te mperature is correlated with a decrease in the intergranular resistanc e. Single-crystal CrO2 is a half-metallic ferromagnet, as the data are interpreted to reflect two types of charge carriers, crossing a grain boundary: those that tunnel between conduction bands of adjacent grai ns and those that hop after residing at a localized state fora time lo ng compared to a spin relaxation time. (C) 1998 American Institute of Physics.