title: 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.
authors.affiliation: Experimentalphysik 2, Universität Augsburg, D-86135 Augsburg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Ebad-Allah
authors.forename: L
authors.initials: L
authors.lastname: Baldassarre
authors.forename: M
authors.initials: M
authors.lastname: Sing
authors.forename: R
authors.initials: R
authors.lastname: Claessen
authors.forename: V A M
authors.initials: VA
authors.lastname: Brabers
authors.forename: C A
authors.initials: CA
authors.lastname: Kuntscher
mesh_terms: D004579:Electron Transport; D004583:Electrons; D052203:Ferrosoferric Oxide / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D044367:Phase Transition; D010825:Physics; D011312:Pressure; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman
chemical_list: D007501:Iron; D052203:Ferrosoferric Oxide