Infrared and Raman Studies of the Verwey Transition in Magnetite

Published

October 16, 2008

Author(s)

L V. Gasparov, D B. Tanner, D B. Romero, H Berger, G Margaritondo, L Forro

Abstract

We present infrared and Raman measurements of magnetite (Fe₃O₄). This material is known to undergo a metal-insulator and a structural transition (Verwey transition) at T_V = 120 K. At temperatures below T_V, we observe a strong gap-like suppression of the optical conductivity below 1000 cm^-1. The structural aspect of the Verwey transition demonstrates itself by the appearance of additional infrared- and Raman-active phonons. The frequencies of the infrared-active phonons show no significant singularities at the transition whereas their linewidths increase. The frequency and linewidth of the Raman-active phonon at 670 cm^-1 changes abruptly at the transition. For T < T_V, we observe fine structures in the infrared and Raman spectra which may indicate strong anharmonicity of the system below the transition. Our estimate of the effective mass of the carriers above the transition is m* nearly equal to} 100 m, where m is the electron mass. Our measurements favor a polaronic mechanism of conductivity and underline the importance of the electron-phonon interaction in the mechamism of the Verwey transition.71.30.+h, 71.38.+i, 78.30.-j, 78.30.Er, 78.40.-q, 78.40.Kc

Citation

Physical Review B (Condensed Matter and Materials Physics)

Pub Type

Journals

Keywords

charge ordering, infrared spectroscopy, magnetite, polaron, Raman scattering, Verwey transition

Citation

Gasparov, L. , Tanner, D. , Romero, D. , Berger, H. , Margaritondo, G. and Forro, L. (2008), Infrared and Raman Studies of the Verwey Transition in Magnetite, Physical Review B (Condensed Matter and Materials Physics) (Accessed September 9, 2024)