Phonon anomalies and charge dynamics in Fe_{1-x}Cu_{x}Cr_{2}S_{4} single crystals

TL;DR

This study investigates phonon behavior and charge dynamics in Fe_{1-x}Cu_{x}Cr_{2}S_{4} single crystals using infrared spectroscopy, revealing how magnetic order and doping influence phonon modes and charge transport.

Contribution

It provides new insights into how doping and magnetic order affect phonon excitations and charge carrier behavior in Fe_{1-x}Cu_{x}Cr_{2}S_{4} compounds.

Findings

Magnetic order strongly influences phonon modes in FeCr_{2}S_{4}

Doping causes continuous phonon evolution despite enhanced screening

Colossal magnetoresistance linked to suppression of spin-disorder scattering

Abstract

A detailed investigation of phonon excitations and charge carrier dynamics in single crystals of Fe_{1-x}Cu_{x}Cr_{2}S_{4} (x = 0, 0.2, 0.4, 0.5) has been performed by using infrared spectroscopy. In FeCr_{2}S_{4} the phonon eigenmodes are strongly affected by the onset of magnetic order. Despite enhanced screening effects, a continuous evolution of the phonon excitations can be observed in the doped compounds with x = 0.2 (metallic) and x = 0.4, 0.5 (bad metals), but the effect of magnetic ordering on the phonons is strongly reduced compared to x = 0. The Drude-like charge-carrier contribution to the optical conductivity in the doped samples indicates that the colossal magneto-resistance effect results from the suppression of spin-disorder scattering.