Electron injection in Te-doped derivatives of Tl2Mn2O7 pyrochlore

J. M. DE PAOLI

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

The American Physical Society.

Lugar: New York; Año: 2001 vol. 64 p. 184436 - 184436

0163-1829

series of Te-substituted pyrochlores of stoichiometry Tl2Mn2-xTexO7 (x< 0.2) has been prepared under high-pressure conditions, at 20 kbar. A neutron-diffraction study demonstrates that Te atoms partially replace Mn cations, adopting a hexavalent oxidation state. The samples are ferromagnetic (FM), showing a maximum TC of 193 K for the x= 0.1 member, considerably higher that that of undoped compound Tl2Mn2O7, with TC= 120 K. This trend implies the reinforcement of an extra FM superexchange interaction mediated by the conduction band. Hall effect shows a dramatic increase in the number of carriers upon Te doping, implying an electronic injection associated with the replacement of Mn4+ by the aliovalent TeVI. The magnetoresistance (MR) is lower than that observed for the undoped pyrochlore, as expected for a higher number of carriers. The high temperature resistivity can be modeled by a thermally activated behavior, via magnetic polaron hopping. The activation energy decreases upon Te d