Thin films of colossal magnetoresistance (MR) material, La0.67Ca0.33MnO3, were implanted with different doses (1011–1015 ions/cm2) of 200 keV Ar+ ions. The implanted samples were examined by ion channeling and x-ray diffraction techniques. The channeling results clearly showed that the magnitude of the induced lattice disorder did not increase greatly for implantation doses up to 5×1013 ions/cm2. In this low dose implantation regime, the magnetoresistance {MR=[R(0)−R(H)]/R(0)} increased by 50%, the peak resistivity went up by two orders of magnitude, and the magnetoresistivity peak temperature decreased by 130 K compared to the original, unimplanted sample. For doses ≥5×1013 ions/cm2, the damage was significant and caused the sample to become semiconducting.

stereochemistry stereochemistry (general, optical resolution) O 0030 -048Chiral Triarylcarbenium Ions in Asymmetric Mukaiyama Aldol Additions.-Title compounds such as (I) and (II), are used as new chiral Lewis acids in asymmetric Mukaiyama aldol additions. Enantiomerically enriched esters (V) are obtained with up to 38% e.