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Berlin 2005 – scientific programme

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MA: Magnetismus

MA 20: Poster:Schichten(1-29),Spintrsp(30-45),Ex-Bias(46-63),Spindyn(64-75),Mikromat.(76-80),Cluster(81-94),Abbv.(95-99),Obflm(100-02),SpElek.(103-09),E-Theo(110-14),Mikromag.(115-16),Spin+PÜ(117-26),Mag.Mat.(127-51),Meth.(152-55),Mol.Mag(156-59),Kondo(160-65

MA 20.164: Poster

Monday, March 7, 2005, 14:00–18:00, Poster TU C

Electronic structure of NiO monolayer on Ag(100) — •L. H. Tjeng1, C.-F. Chang1, S. Altieri2, S. Heise1, M. W. Haverkort1, Z. Hu1, S. V. Streltsov3, V. I. Anisimov3, H. H. Hsieh4, H.-J. Lin5, D.-J. Huang5 und C.T. Chen51II. Physikalisches Institut, Universität zu Köln,Zülpicher Str. 77, 50937 Köln, Germany — 2INFM, Modena,Italy — 3Institute of MetalPhysics, Ekaterinburg, Russia — 4Chung Cheng Institute of Technology, Taiwan — 5NSRRC, Taiwan

We have investigated the electronic structure of a NiO monolayer deposited on top of a Ag(100) substrate. Using x-ray absorption spectroscopy we found that the Ni ions are in the 3d8 (2+) valence state, with one hole in a 3d3z2r2 orbital and another in a 3dx2y2, very similar to bulk NiO. From the polarization dependence we observed nevertheless that the 3d3z2r2 orbital in the NiO monolayer is somewhat less unoccupied than in bulk NiO and that there is a large 3d3z2r2 −3dx2y2 crystal field splitting. Our LDA+U calculations show that the unoccupied 3d3z2r2 orbital is not pushed up so strongly above the Fermi level because in the monolayer there are no oxygens above or below it to hybridize with. This 3d3z2r2 forms a band via the Ag sp-states, with a low energy tail extending below the Fermi level. This is confirmed by our photoemission data, which show a clear Fermi cut-off in the Ni 3d. In other words, the monolayer is metallic. Moreover, except for a rigid energy shift, the photoemission spectra of the NiO monolayer and bulk NiO look rather similar. We have more spectroscopic data to suggest that the NiO monolayer on Ag is actually a Kondo lattice system.

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