Polaron physics and crossover transition in magnetite probed by pressure-dependent infrared spectroscopy

Abstract

The optical properties of magnetite at room temperature were studied by infrared reflectivity measurements as a function of pressure up to 8 GPa. The optical conductivity spectrum consists of a Drude term, two sharp phonon modes, a far-infrared band at around 600 cm${}^{-1}$, and a pronounced mid-infrared absorption band. With increasing pressure both absorption bands shift to lower frequencies and the phonon modes harden in a linear fashion. Based on the shape of the MIR band, the temperature dependence of the dc transport data, and the occurrence of the far-infrared band in the optical conductivity spectrum the polaronic coupling strength in magnetite at room temperature should be classified as intermediate. For the lower-energy phonon mode an abrupt increase of the linear pressure coefficient occurs at around 6 GPa, which could be attributed to minor alterations of the charge distribution among the different Fe sites.

7 pages, 7 figures

References in corpus (7)

• Resonant X-ray diffraction studies on the charge ordering in magnetite
• Origin of the Verwey transition in magnetite: Group theory, electronic structure, and lattice dynamics study
• High-energy photoemission on Fe3O4: Small polaron physics and the Verwey transition
• Pressure-induced deconfinement of the charge transport in the quasi-one-dimensional Mott insulator (TMTTF)_2AsF_6
• Optical properties of small polarons from dynamical mean-field theory
• Pressure-induced changes in the optical properties of quasi-one-dimensional $\beta$-Na${}_{0.33}$V${}_2$O${}_5$
• Effect of pressure on the polarized infrared optical response of quasi-one-dimensional LaTiO${}_{3.41}$

Cited by in corpus (3)

• Temperature-Dependence of Magnetically-Active Charge Excitations in Magnetite across the Verwey Transition
• Polarization-dependent infrared reflectivity study of Sr${}_{2.5}$Ca${}_{11.5}$Cu${}_{24}$O${}_{41}$ under pressure: Charge dynamics, charge distribution, and anisotropy
• Optical conductivity of the metallic pyrochlore iridate Pr${}_2$Ir${}_2$O${}_7$: Influence of spin-orbit coupling and electronic correlations on the electronic structure