Infrared Studies of a La_{0.67}Ca_{0.33}MnO_3 Single Crystal: Optical Magnetoconductivity in a Half-Metallic Ferromagnet

TL;DR

This study investigates the infrared optical properties of La_{0.67}Ca_{0.33}MnO_3 single crystals across various temperatures and magnetic fields, revealing changes consistent with theoretical models of double exchange and Jahn-Teller effects, and observing significant magnetoconductivity near the Curie temperature.

Contribution

It provides experimental infrared data on a manganite single crystal, supporting theoretical models of electron-phonon interactions and magnetic effects in half-metallic ferromagnets.

Findings

Optical conductivity shifts from Drude-like to broad peak below T_C.

Strong optical magnetoconductivity observed near T_C.

Features align with double exchange and Jahn-Teller interaction theories.

Abstract

The infrared reflectivity of a $\rm La_{0.67}Ca_{0.33}MnO_3$ single crystal is studied over a broad range of temperatures (78-340 K), magnetic fields (0-16 T), and wavenumbers (20-9000 cm$^{-1}$). The optical conductivity gradually changes from a Drude-like behavior to a broad peak feature near 5000 cm$^{-1}$ in the ferromagnetic state below the Curie temperature $T_C=307 K$. Various features of the optical conductivity bear striking resemblance to recent theoretical predictions based on the interplay between the double exchange interaction and the Jahn-Teller electron-phonon coupling. A large optical magnetoconductivity is observed near $T_C$.