X-ray absorption spectroscopy of Mg doped Fe3O4 thin films

Superconductivity induced in iron telluride films by low-temperature oxygen incorporation

“…Such a peak is a direct result of Fe 3d orbitals hybridizing with oxygen 2 p orbitals [23]. The relative photon energy position of the FeO x pre-peak to the main MgO peak is in very good agreement with the peak spacing reported in XAS studies of Fe 1−x Mg x O y [24].…”

Electronic structure of room-temperature ferromagnetic Mg1−xFexOy thin films

“…31 However, such splitting is not as resolved in our data as reported in Ref. 26, which may plausibly be attributed to the low Fe content in the host MgO matrix. The absence of p 1 in the Fe doped MgO thin films indicate that the conduction band minimum (CBM) shifts up towards higher energies on Fe doping.…”

“…Following these theoretical and experimental findings, we find the shoulder feature to reflect the unoccupied O 2p states and attribute the origin of the pre-edge feature (p*) to the transitions into the chargetransfer band between O 2p-Fe 3d (acceptor state). [26][27][28][29] The transition metal 3d band has previously been reported to consist of two peaks, identified as the t 2g -and e gsymmetry bands, separated by a ligand-field splitting. 28 Such splitting arises due to the repulsion between the 3d electrons and the negatively charged anions or dipolar ligands, and their baricentre of the degenerate levels is raised.…”

“…30 For a theoretical interpretation of such findings, in, e.g., La 2-x Sr x CuO 4 , the authors in Ref. 26 have used the three-band Hubbard model to show that the energy separation between the shoulder feature (p 1 ), and the pre-edge (p*) feature represents the charge-transfer gap, re-normalized by core-hole excitonic correlation. Following these theoretical and experimental findings, we find the shoulder feature to reflect the unoccupied O 2p states and attribute the origin of the pre-edge feature (p*) to the transitions into the chargetransfer band between O 2p-Fe 3d (acceptor state).…”

Understanding the magnetic interaction between intrinsic defects and impurity ions in room-temperature ferromagnetic Mg1−xFexO thin films

“…Instead, insight on the origin of B can be obtained from the studies of charge compensation in cuprate superconductors where the holes compensating impurity charge lie in the unoccupied O 2p band, and energy difference (Δ) between the charge donor induced spectral feature and acceptor feature corresponds to a charge transfer gap, re-normalized by core-hole excitonic correlation [35][36][37]. This analogy suggests that O 2p-Fe 3d charge transfer to become more pronounced with increasing dopant concentrations, as O 2p acceptor states (at 533 eV) would be substantially reduced [12,33].…”