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Probing the surface phase diagram of Fe_{3}O_{4}(001) towards the Fe-rich limit: Evidence for progressive reduction of the surface

Physical Review B 87(19): 195410

Autoren/Herausgeber: Novotny Z
Mulakaluri N
Edes Z
Schmid M
Pentcheva R
Diebold U
Parkinson GS
Erschienen: 2013
Reduced terminations of the Fe3O4(001) surface were studied using scanning tunneling microscopy, x-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). Fe atoms, deposited onto the thermodynamically stable, distorted B-layer termination at room temperature (RT), occupy one of two available tetrahedrally coordinated sites per (√2×√2)R45° unit cell. Further RT deposition results in Fe clusters. With mild annealing, a second Fe adatom per unit cell is accommodated, though not in the second tetrahedral site. Rather both Fe atoms reside in octahedral coordinated sites, leading to a “Fe-dimer” termination. At four additional Fe atoms per unit cell, all surface octahedral sites are occupied, resulting in a FeO(001)-like phase. The observed configurations are consistent with the calculated surface phase diagram. Both XPS and DFT+U results indicate a progressive reduction of surface iron from Fe3+ to Fe2+ upon Fe deposition. The antiferromagnetic FeO layer on top of ferromagnetic Fe3O4(001) suggests possible exchange bias in this system.

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