Small-polaron band versus hopping conduction in Fe3O4

The electrical small-polaron (SP) conductivity of Fe 3 O 4 is calculated above the Verwey transition taking into account the polaronic short-range order. It is shown that the conductivity results from the superposition of SP band and SP hopping conduction. Concerning the DC conductivity below room temperature, the SP band conduction is the dominant mechanism. The observed maximum in the optical conductivity near 0.2 eV is explained as an SP hopping effect.