Regensburg 2004 – scientific programme
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O: Oberflächenphysik
O 28: Postersitzung (Elektronische Struktur, Grenzfläche fest-flüssig, Halbleiteroberflächen und -grenzflächen, Magnetismus und Symposium SYXM, Methodisches, Nanostrukturen, Oberflächenreaktionen, Teilchen und Cluster, Zeitaufgelöste Spektroskopie)
O 28.81: Poster
Wednesday, March 10, 2004, 16:00–19:00, Bereich C
Anomalous ferromagnetism of monatomic Co wire at the Pt(111) surface step edge — •Peter M. Oppeneer1, Alexander B. Shick2, and Frantisek Máca2 — 1IFW Dresden — 2Inst. of Physics, ASCR, Prague
We report a first-principles investigation of the anomalous ferromagnetism of a quasi-one-dimensional Co chain decorating the Pt(111) step edge. Our calculations demonstrate that the symmetry breaking at the Pt step leads to an easy magnetization axis at an anomalous angle of ∼20∘ towards the Pt step, in semi-quantitative agreement with the experimentally observed peculiar easy axis at an angle of ∼ 40∘ [P. Gambardella et al., Nature 416, 301 (2002)]. The computed hard magnetization axis direction also corresponds well to the experimentally observed hard axis. A (T=0) magnetocrystalline anisotropy energy of 3 meV/Co is calculated in good agreement with the experimental value of ∼ 2 meV/Co at T=45 K. On account of the symmetry breaking the Co spin and orbital moments become noncollinear, even in the case of a collinear ferromagnetic spin arrangement. We also performed LSDA+U calculations, with which a significant enhancement of the Co orbital magnetic moment is achieved already when modest electron correlations (small U) are taken into account.