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Regensburg 2004 – wissenschaftliches Programm

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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 28.84: Poster

Mittwoch, 10. März 2004, 16:00–19:00, Bereich C

X-ray magneto-optical sum rules in small Co clusters — •Kai Fauth1,2, Markus Heßler1,2 und Gisela Schütz21Physikalisches Institut der Universität Würzburg, Am Hubland, 97074 Würzburg — 2MPI für Metallforschung, Heisenbergstraße 3, 70569 Stuttgart

The so-called spin and orbital sum rules [1,2] in x-ray magnetic circular dichroism (XMCD) spectroscopy are often believed to apply with reasonable accuracy in the case of the late 3d transition metals and their compounds, if the magnetic dipole term Tz can be neglected. Strong deviations can occur due to symmetry breaking such as given at surfaces, causing the magnetic dipole term to contribute significantly to the spin sum rule, while not contributing to the magnetization. Much less is known in the case of small clusters. We have derived magnetic moments of superparamagnetic Co55 clusters from XMCD at various applied magnetic fields. We find that the moments thus obtained from the magnetization curve and those determined separately from the sum rules agree to within 10%. This result sets an upper limit for the importance of Tz in these clusters.
B. T. Thole et al. , Phys. Rev. Lett. 68, 1943 (1992)
P. Carra et al. , Phys. Rev. Lett. 70, 694 (1993)

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