Dresden 2011 – scientific programme

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MO: Fachverband Molekülphysik

MO 10: Cluster

MO 10.9: Talk

Tuesday, March 15, 2011, 12:30–12:45, MER 02

Spin and orbit moments of super paramagnetic Cobalt clusters from XMCD investigation of isolated ions by the GAMBIT experiment — •Jennifer Meyer¹, Matthias Tombers¹, Heinrich Kampschulte¹, Gereon Niedner-Schatteburg¹, Sergey Peredkov², Sven Peters², Matthias Neeb², and Wolfgang Eberhardt² — ¹Fachbereich Chemie und Forschungszentrum OPTIMAS, TU Kaiserslautern — ²Helmholtz-Zentrum, Campus Adlershof, BESSY II, Berlin

X-ray induced circular dichroism (XMCD) arises in magnetized samples upon resonant inner shell ionization once their spins and orbit moments are sufficiently aligned e.g. by a strong external field. We operate an ion trap (GAMBIT) at BESSY II in Berlin to record XMCD spectra of isolated clusters. By standard sum rule analysis we have deduced the partial spin and orbit contributions of Cobalt cluster cations Co_n⁺ (8 ≤ n ≤ 23) void of coupling to any substrate. It shows that orbit moments (per atom) in the clusters are significantly enhanced as compared to those of bulk Cobalt whereas spin contributions show little variation. The sum of both contributions compares well with the total moments from prior Stern-Gerlach experiments. Spin contributions may diminish further once a conceivable - yet undetermined - magnetic anisotropy would be taken into account. Our current experiments do not reveal evidence for such anisotropy. These obtained results provide benchmark data for further modeling. This project is part of the new Transregional Collaborative Research Center SFB TRR 88 "3MET".