1202.4431 (J. Ebad-Allah et al.)

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

J. Ebad-Allah, L. Baldassarre, M. Sing, R. Claessen, V. A. M. Brabers, C. A. Kuntscher

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.

View original: http://arxiv.org/abs/1202.4431