LOCAL SPIN-DENSITY FUNCTIONAL INVESTIGATIONS OF THE CHEMICAL BONDING AND MAGNETISM IN THE CMR PYROCHLORE COMPOUND TL2MN2O7

The electronic and magnetic structures of the ferromagnetic pyrochlore compound Tl2Mn2O7, exhibiting colossal magnetoresistance (CMR), are s elf-consistently calculated within the local spin density functional t heory using the augmented spherical wave (ASW) method. The influence o f mixing between the different l-valence states on the chemical bondin g is discussed from the site projected densities of states (DOS) and f rom the crystal orbital overlap population (COOP). From this a descrip tion of the nature of chemical bonding is proposed in relation with th e development of the magnetic moment of Mn (2.77 mu(B)) which is found in good agreement with experimental results. Besides, from the calcul ations a new magnetic property of a weakly half-metallic ferromagnet i s proposed.