Berlin 2012 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 49: Joint Session "Surface Magnetism III" (jointly with O)

MA 49.4: Vortrag

Donnerstag, 29. März 2012, 16:00–16:15, BH 243

Structural aspects of magnetic coupling in a bilayer CoO(111) on Ir(100) — Florian Mittendorfer¹, Raimund Podloucky², and •Josef Redinger¹ — ¹Inst. of Applied Physics, Vienna University of Technology, Vienna, Austria — ²Inst. of Physical Chemistry, University of Vienna, Vienna, Austria

Experimentally, stoichiometric CoO is found to form a (111)-like hexagonal c(10x2) bilayer on the square fcc Ir(100) surface [1]. Besides lateral displacements and vertical bucklings two distinct local building blocks can be detected: hexagonal BN-like almost co-planar Co-O fragments and NaCl-type O atoms above Co triangles. Consequently, different magnetic couplings for the different arrangements should be expected, which will be further modified by the coupling to the non-magnetic substrate. We have performed DFT and DFT+U calculations for the proposed c(10x2) CoO(111)/Ir(100) structure and structural variants and also for the NaCl (RS) and Wurtzite (WZ) type bulk phases. Quite interestingly for the bulk phases PBE and even HSE predict the WZ to be the stable one, a trend which could only be reversed in PBE+U calculations for high values of U. Furthermore ferromagnetic coupling for bulk WZ CoO is found to be energetically much closer to the antiferromagnetic groundstate as compared to RS CoO. For the bilayer CoO(111)/Ir(100) systems this translates into a rather complex magnetic arrangement of ferro and antiferromagnetc couplings, which could be easily modified by small changes to the geometrical structures as determined by the CoO/Ir interface.
C. Ebensperger et al., Phys Rev. B81, 235405 (2010).