High-energy photoemission on Fe3O4: Small polaron physics and the Verwey transition

We have studied the electronic structure and charge ordering (Verwey) transition of magnetite (Fe3O4) by resonant soft x-ray photoemission at the Fe 2p-3d threshold. Due to the enhanced probing depth and the use of different surface prepns. we are able to distinguish surface and vol. contributions to the spectra. The intrinsic spectral wt. distribution near the chem. potential and its temp. dependence give evidence of strong polaron effects consistent with both d.c. and optical cond. The charge carriers in magnetite are strongly bound small polarons of the Jahn-Teller type. The stability of the charge order is thus not only driven by nearest-neighbor Coulomb interaction but strongly dominated by elastic lattice contributions. [on SciFinder (R)]