Colossal magnetoresistance in La1-xLixMnO3

La1-xLixMnO3 (x = 0, 0.1, 0.2, and 0.3) were synthesized by using conventio nal solid state reaction and partial melting technique. The compounds were determined to be of rhombohedral structure by x-ray powder diffraction. For the x = 0.2 and x = 0.3 samples, room temperature neutron powder diffracti on patterns were collected and analyzed with the Rietveld method. The analy sis showed that the Li substitutes onto the La site in the rhombohedral per ovskite lattice. Resistivities were measured between 4.2 K and room tempera ture in the magnetic fields of 0, 1, 2, 4, 8, and 13 T. A wide semiconducto r-metal transition at temperatures between 160 and 210 K or between 200-230 K were observed for both samples with x = 0.2 and 0.3, respectively. Large magnetoresistances above 20%-80% were achieved at fields from null to 13 T over a wide temperature range from the ferromagnetic transitions down to 4 .2 K. However, the x = 0 and 0.1 samples show a semiconducting behavior in resistivity measured between 77 and 300 K. (C) 1998 American Institute of P hysics.