Effects of unreconstructed and reconstructed polar surface terminations on growth, structure, and magnetic properties of hematite films

The effects of polar surface stabilization mechanisms on the film growth, phase composition, surface and interface structure, and magnetic properties are explored for polar oxide interfaces formed by the epitaxial growth of hematite films on magnesia and alumina single crystals. Growth of α-Fe ₂O ₃(0001) on the (√3×√3)R30° and (2 × 2) reconstructed MgO(111) surfaces results in formation of a self-organized Fe ₃O ₄(111) interfacial nano buffer that persists after growth. The interfacial magnetite-like phase is absent from the hematite films formed on hydrogen-stabilized unreconstructed MgO(111)-(1 × 1) and on Al ₂O ₃(0001)-(1 × 1) surfaces under equivalent conditions. This study suggests that in addition to the customary strain, spin, and band-gap engineering, control of surface polarity stabilization could also be important for electronic and magnetic device engineering.