Dresden 2011 – scientific programme
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O: Fachverband Oberflächenphysik
O 91: Epitaxy and growth: Oxides and insulators
O 91.1: Talk
Thursday, March 17, 2011, 17:15–17:30, WIL C307
DFT study of structure and magnetism of CoO(111) bilayers on Ir(100) — Florian Mittendorfer1, •Josef Redinger1, Raimund Podloucky2, and Michael Weinert3 — 1Inst. of Applied Physics, Vienna University of Technology, Vienna, Austria — 2Inst. of Physical Chemistry, University of Vienna, Vienna, Austria — 3Dept. of Physics, University of Wisconsin-Milwaukee, Milwaukee, USA
Experimentally, a hexagonal CoO(111) bilayer is formed on square fcc Ir(100) leading to a c(10x2) superstructure (9 CoO/10 Ir) with large lateral displacements and vertical buckling (5 high, 4 low) of the Co atoms [1]. The 4 O atoms above the Co atoms show a (111) NaCl-type arrangement, while the remaining 5 O atoms are found about 1Å lower, almost coplanar with Co, resembling a hexagonal BN-like arrangement. We have performed DFT calculations for the proposed c(10x2) structure and found the structure to be energetically stable and in good agreement with experimental LEED data, provided proper care is taken for the rather complex magnetic arrangement. The 5 high Co atoms couple anti-ferromagnetically (AF), while ferromagnetic (F) coupling is stabilized by the Ir substrate for the 4 low Co atoms. Considering a CoO registry shift on the Ir(100) substrate a new structure with similar energy emerges, but now with 5 high and 4 low Co/O atoms, resembling 9x2 CoO/Pd(100) [2]. The 5 low Co atoms close to Ir favor once more F-coupling, while the remaining 4 high Co couple AF to the former, abandoning an alternating AF-coupling along the high Co rows. [1] C. Ebensperger et al., Phys Rev. B81, 235405 (2010). [2] L. Gragnaniello et al., Surf. Sci. 604, 2002 (2010).