Electronic Raman scattering in magnetite: Spin versus charge gap
We report Raman-scattering data of single crystals of magnetite (Fe3O4) with Verwey transition temperatures (T-v) of 123 and 117 K, respectively. Both single crystals reveal broad electronic background extending up to 900 wave numbers (similar to 110 meV). Redistribution of this background is observed when samples are cooled below T-v. In particular, spectra of the low-temperature phase show diminished background below 300 wave numbers followed by an enhancement of the electronic background between 300 and 400 wave numbers. To enhance the effect of this background redistribution, we divide the spectra just below the transition by the spectra just above the transition. A resultant broad peaklike feature is observed centered at 370 +/- 40 wave numbers (45 +/- 5 meV). The peak position of this feature does not scale with the transition temperature. We discuss two alternative assignments of this feature to a spin or charge gap in magnetite.
Keywords: energy gap ; iron compounds ; magnetic semiconductors ; magnetic transition temperature ; metal-insulator transition ; Raman spectra ; spin dynamics ; Verwey Transition ; Fe3O4 ; Excitations ; Ferrites ; Polarons ; Point ; Light
Record created on 2010-11-30, modified on 2016-08-09