Discerning element and site-specific fluctuations of the charge-orbital order in Fe3O4 below the Verwey transition

Despite countless experimental probes into magnetite's electronic structure across the Verwey transition Fe3O4, the exact origin of this archetypical metal-insulator transition remains a puzzle. Advanced x-ray diffrac-tion techniques have mostly resolved the monoclinic structure of the insulating phase, including interatomic bond lengths, but the complexity of the charge-orbitally ordered state is difficult to disentangle. We combined resonant elastic x-ray scattering and x-ray photon correlation spectroscopy to probe charge-orbital fluctuations in the insulating state of magnetite. By accessing the Bragg forbidden (00 1/2 )c peak at the oxygen K-edge, we complement our previous study on the iron L-3-edge to reveal the dynamics of the iron 3d and oxygen 2p orbital domains. Our new results reveal a decoupling of the orbital correlation lengths between the oxygen 2p states and site-specific iron 3d states, and we further show charge-orbital domain fluctuations at the iron t(2g) orbital sites of trimeron chains. These results also demonstrate an experimental method capable of distinguishing electronic dynamics between the oxygen ligands and the transition metal that underpins emergent behaviors in complex oxides.

Automated summary

We studied charge-orbital fluctuations in the insulating state of magnetite using resonant elastic x-ray scattering and x-ray photon correlation spectroscopy. Our results revealed the dynamics of the iron 3d and oxygen 2p orbital domains, showing a decoupling of the orbital correlation lengths between the oxygen ligands and site-specific iron 3d states. We also observed charge-orbital domain fluctuations at the iron t(2g) orbital sites of trimeron chains.