Complex electronic, magnetic, and structural transformations in FeO

Iron oxides are important materials for Geoscience but also for basic science and applied technologies (Kupenko et al., 2019). Iron monoxide is likely to be the final constituent of the evolution of subducted banded iron formations and might be a source of the low-velocity zones at the Earth’s core-mantle boundary (Dobson and Brodholt, 2005). The stability and high-pressure properties of FexO could, thus, determine the fate of banded iron formations and their potential role in processes in Earth and planetary interiors, including controls on redox cycles.

FexO has the NaCl (B1) structure at ambient pressure and temperature and transforms into rhombohedral distorted-B1 phase (rB1) at about 16 GPa. A further transition from a rhombohedral rB1 phase to a hexagonal B8 phase has been proposed at 74 GPa and 900 K (Fei and Mao, 1994). Although numerous studies were focused on the investigation of the electronic and magnetic properties and phase diagram of FexO, information on the Fe2+/Fe3+ interplay, magnetic and structural coupling of FexO at high pressures and high temperature are very limited.

We will present our investigation on the pressure dependence of the electronic, magnetic and structural properties of FexO by means of Synchrotron Mössbauer Source spectroscopy and Single-Crystal X-ray diffraction with diamond anvil cells up to 94 GPa and 1200 K. We will discuss the interplay between Fe2+ and Fe3+ and its effects on the electronic and magnetic properties of FexO and their potential role in the mineralogy, chemistry, and physics of the Earth’s deep interior.