Regensburg 2004 – wissenschaftliches Programm

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O: Oberflächenphysik

O 12: Magnetismus in reduzierten Dimensionen

O 12.3: Vortrag

Montag, 8. März 2004, 16:15–16:30, H45

Valence band electronic structure and chemical reactivity in MgO/Fe(100) and MgO/Co/Fe(100) oxide-metal interfaces grown on GaAs(100) — •Liu-Niu Tong¹, Frank Matthes¹, and C.M. Schneider² — ¹Leibniz Institut für Festkörper- und Werkstoffforschung — ²Institut für Elektronische Eigenschaften, Forschungszentrum

The interface electronic structure of MgO/Fe(100) and MgO/Co/ Fe(100) films epitaxially grown on GaAs(100) was studied by employing spin-polarized photoemission spectroscopy (SPPES) and magnetic circular dichroism (MCD) techniques. With increasing excitation energy from 30 eV to 60 eV, we observe an enhanced spectral intensity in the SPPES data of pure Fe for transitions from bulk Δ¹ and Δ⁵ initial states near the Fermi energy that is accompanied with an increase in the detected spin polarization. After covering the Fe(100) surface by 0.5 ML MgO, the shape of the Fe Δ⁵ minority-spin peak becomes significantly broadened, while the shape of the Fe Δ¹ majority-spin peak is only weakly affected. Additionally, we observed that 1 ML MgO on top of Fe(100) suppresses almost all contribution from the Fe Δ⁵ minority transition in the measured spin polarization data. This observed effect is especially strong for an excitation energy of 40 eV. Furthermore, our MCD data show that the O 2p peak is shifting towards the Fermi level as a function of time after preparation, indicating a slow change in the film chemistry. This chemical reaction can also be seen for MgO/Fe samples that were immediately covered after preparation with an additional Fe film on top.