ELECTRONIC BAND-STRUCTURE STUDY OF COLOSSAL MAGNETORESISTANCE IN TL2MN2O7

The electronic structure of Tl2Mn2O7 was examined by performing tight binding band calculations. The overlap between the Mn t(2g)- and Tl 6s -block bands results in a partial filling of the Tl 6s-block bands. Th e associated Fermi surface consists of 12 cigar-shape electron pockets with each electron pocket about 1/1000 of the first Brillouin zone in size. The Tl 6s-block bands have orbital contributions from the Mn at oms, and the carrier density is very low. These are important for the occurrence of a colossal magnetoresistance in Tl2Mn2O7. Copyright (C) 1997 Elsevier Science Ltd