Carrier density change in Colossal Magnetoresistive Pyrochlore Tl2Mn2O7

TL;DR

This study investigates how carrier density in Tl2Mn2O7, a colossal magnetoresistive pyrochlore, varies with temperature and magnetic field, revealing its role in the material's magnetoresistance behavior.

Contribution

It demonstrates that carrier density changes with temperature and magnetic field in Tl2Mn2O7, highlighting a conduction-band-edge shift due to s-d interaction as a key mechanism.

Findings

Carrier density increases near TC with temperature decrease.

Carrier density increases with magnetic field strength.

Negligible anomalous Hall coefficient due to small skew scattering.

Abstract

Hall resistivity and magneto-thermopower have been measured for colossal magnetoresistive Tl2Mn2O7 over wide temperature and magnetic-field ranges. These measurements revealed that a small number of free electron-like carriers is responsible for the magneto-transport properties. In contrast to perovskite CMR materials, the anomalous Hall coefficient is negligible even in the ferromagnetic state due to negligibly small skew scattering. The characteristic feature in Tl2Mn2O7 is that the carrier density changes with temperature and the magnetic field. The carrier density increases around TC as the temperature is lowered or as the magnetic field is increased, which explains the CMR of this material. The conduction-band-edge shift, which is caused by the strong s-d interaction between localized Mn moments and s-like conduction electrons, is a possible mechanism for the carrier density change.