Spin dynamics of CMR pyrochlore Tl2Mn2O7

Abstract The observed spin dynamics in colossal magnetoresistive pyrochlores is in stark contrast with that of perovskite manganites. We performed spin wave calculations for Tl 2 Mn 2 O 7 , using the microscopic generic model for the compound proposed recently. Through a canonical transformation we determine the renormalization of the ferromagnetic spin waves related to local Mn 4+ spins, by their coupling with the conduction electrons. We obtain excitations such as measured by neutron scattering experiments, characteristic of 3-D isotropic ferromagnets.