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We have studied the electronic structure of bulk single crystals andepitaxial films of magnetite Fe$_3$O$_4$. Fe $2p$ core-level spectra show cleardifferences between hard x-ray (HAX-) and soft x-ray (SX-) photoemissionspectroscopy (PES), indicative of surface effects. The bulk-sensitive spectraexhibit temperature ($T$)-dependent charge excitations across the Verweytransition at $T_V$=122 K, which is missing in the surface-sensitive spectra.An extended impurity Anderson model full-multiplet analysis reveals roles ofthe three distinct Fe-species (A-Fe$^{3+}$, B-Fe$^{2+}$, B-Fe$^{3+}$) below$T_V$ for the Fe $2p$ spectra, and its $T-$dependent evolution. The Fe $2p$HAXPES spectra show a clear magnetic circular dichroism (MCD) in the metallicphase of magnetized 100-nm-thick films. The model calculations also reproducethe MCD and identify the magnetically distinct sites associated with the chargeexcitations. Valence band HAXPES shows finite density of states at $E_F$ forthe polaronic metal with remnant order above $T_V$, and a clear gap formationbelow $T_V$. The results indicate that the Verwey transition is driven bychanges in the strongly correlated and magnetically active B-Fe$^{2+}$ andB-Fe$^{3+}$ electronic states, consistent with resistivity and bulk-sensitiveoptical spectra.

Temperature-Dependence of Magnetically-Active Charge Excitations in Magnetite across the Verwey Transition