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

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.

arXiv comment8 pages, 6 figures

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• Magneto-electric properties and low-energy excitations of multiferroic FeCr2S4
• Spin-phonon interactions and magnetoelectric coupling in Co${}_4$$B_2$O${}_9$ ($B$ = Nb, Ta)
• Optical magnetoelectric effect in the polar honeycomb antiferromagnet Fe2Mo3O8
• On the complexity of spinels: Magnetic, electronic, and polar ground states