We report significant enhancement of magnetoresistance (MR) in melt-processed La0.67Ca0.33MnO3 (LCM) and in Ho-doped LCM samples. The LCM system exhibits surprising enhancement of metal-insulator transition (T-IM) that coincides with the Curie transition temperature (T-c), T-IM approximate to T-c, illustrating the enhanced percolative transport and spin-polarization through grain boundaries. Surprisingly, 1 mol % of addition of Ho enhances T-c of similar to 70 K with remarkable colossal MR. The nanoscale Ho distribution is consistent with the magnetic inhomogeneity-induced MR due to phase segregation in Ho-doped sample whereas charge-segregation picture is valid for undoped LCM. (C) 2001 American Institute of Physics.
Copyright:Copyright [2001]. All efforts have been made to respect the copyright to the best of our knowledge. Inadvertent omissions, if brought to our notice, stand for correction and withdrawal of document from this repository.