Origin of ferromagnetism and its pressure and doping dependence in Tl₂Mn₂O₇

Abstract

Using the Nth order muffin-tin obital downfolding technique, we investigate the origin of ferromagnetism in pyrochlore Tl₂Mn₂O₇. It is found to be driven by a hybridization induced spin polarization of delocalized charge carriers derived from Tl-s and O-p states. The mean-field estimate of the ferromagnetic transition temperature T_c estimated using computed exchange integrals are found to be in good agreement with measurements. We find an enhancement of T_c for moderate doping with nonmagnetic Sb and a suppression of T_c upon application of pressure, both in agreement with experimental findings.