High-resolution photoemission spectroscopy of the Verwey transition inFe3O4

We study the first-order Verwey transition in single-crystal ${\mathrm{Fe}}_3$ ${\mathrm{O}}_4$ using high-resolution temperature-dependent (100–300 K) photoemission spectroscopy. The near-Fermi-level (${\mathit{E}}_{\mathit{F}}$) spectrum exhibits a clear gap of ∼70 meV in the occupied part of the density of states (DOS) in the low-temperature semiconducting phase. The gap is closed above the transition temperature ${\mathit{T}}_{\mathit{V}}$=122 K, establishing a metal-semiconductor transition. The Fe 3d derived features arising from ${\mathrm{Fe}}^{3+}$ (${\mathit{e}}_{\mathit{g}}^2$) majority- and ${\mathrm{Fe}}^{2+}$ (${\mathit{t}}_{2\mathit{g}}^1$) 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 ${\mathit{E}}_{\mathit{F}}$ increases systematically in the metallic phase. The results indicate the existence of, and a gradual change in, the short-range order for T>${\mathit{T}}_{\mathit{V}}$, which causes the nonmetalliclike electrical conductivity observed just above ${\mathit{T}}_{\mathit{V}}$.