Electronic structure of Fe₃O₄ across the verwey transition

A study of the first-order Verwey transition in single-crystal Fe₃O₄ using high-resolution temperature dependent (100 - 300K) photoemission spectroscopy is reported. Fe₃O₄ exhibits a gap of ∼ 70 meV in the occupied part of the density of states(DOS) below the transition temperature, T_v = 122 K. On increasing the temperature above T_v, the gap in the DOS is closed thus establishing a metal-semiconductor transition. The Fe 3d derived features arising from Fe³⁺ (eg²) majority and Fe²⁺ (t2_g¹) minority spin states responsible for the transition, retain their character just above the transition but merge into a single feature by 300 K. Simultaneously, the DOS at EF increases systematically in the metallic phase. The results indicate a gradual change in the short-range order for T > T_v which gives rise to the non-metallic like electrical conductivity observed just above T_v.