Local spin density functional investigations of the chemical bonding and magnetism in the CMR pyrochlore compound Tl2Mn2O7

Abstract

The electronic and magnetic structures of the ferromagnetic pyrochlore compound Tl ₂ Mn ₂ O ₇ , exhibiting colossal magnetoresistance (CMR), are self-consistently calculated within the local spin density functional theory using the augmented spherical wave (ASW) method. The influence of mixing between the different l-valence states on the chemical bonding is discussed from the site projected densities of states (DOS) and from the crystal orbital overlap population (COOP). From this a description of the nature of chemical bonding is proposed in relation with the development of the magnetic moment of Mn (2.77 µ _B ) which is found in good agreement with experimental results. Besides, from the calculations a new magnetic property of a weakly half-metallic ferromagnet is proposed.