Ultrafast dynamics in the colossal magnetoresistance pyrochlore Tl2Mn2O7
Abstract
Colossal magnetoresistance (CMR) materials have recently received a great deal of attention, both due to fundamental interest in CMR as well as potential applications in areas such as magnetic sensing and recording. The pyrochlore Tl_2Mn_2O7 exhibits CMR below its Curie temperature (T_c) of ∼ 120 K, but the CMR mechanism is expected to be very different from that in the ferromagnetic perovskite manganites. Optical conductivity measurements revealed a transition from an insulator-like to a metallic structure as the temperature was tuned below T_c, with a corresponding increase in the carrier density and change of the reflectivity with temperature near the plasma edge. In this work, we use an optical pump, mid-IR probe system to investigate ultrafast dynamics in Tl_2Mn_2O7 near the plasma edge of the reflectivity as a function of temperature. We observe distinct changes as the temperature is tuned through T_c, in particular a large increase in the peak amplitude and offset of the signal near T_c. This corresponds to a long-lived carrier density increase which may be due to reduced spin scattering resulting from dynamically enhanced ferromagnetic ordering.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MARL24004P