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MA: Fachverband Magnetismus

MA 3: Bio- and Molecular Magnetism

MA 3.2: Talk

Monday, March 14, 2011, 11:15–11:30, HSZ 401

Geometrical Frustration in Molecular Spin Triangles with S=1/2, 5/2 — •Nicolas Yèche¹, Andrei Zvyagin^1,2, Daniel Plaul³, Dirk Schuch³, Winfried Plass³, Eric Kampert⁴, Til Dellmann¹, Christopher Baines⁵, Gwendolyne Pascua⁵, Hans-Henning Klauß¹, and Hubertus Luetkens⁵ — ¹Institut für Festkörperphysik ,TU Dresden — ²Institute for Low Temperature Physics and Engineering of the NAS of Ukraine, Kharkov — ³Institut für Anorganische Chemie, Uni Jena — ⁴Hochfeldlabor Dresden, FZ Dresden-Rossendorf — ⁵Paul Scherrer Institute, Villingen, Switzerland

In the study of finite geometrically frustrated system, the simplest problems that can be considered are paradoxically some of the hardest ones to observe experimentally. Thanks to sophisticated organic ligands, independent triangles of Cu(II) (S=1/2) and Fe(III) (S=5/2) were synthesized. Investigations carried out with macroscopic (pulsed and static field magnetization) and local probe techniques (µSR and ⁵⁷Fe mössbauer spectroscopy) show characteristic behavior of frustrated systems. Comparison of the magnetization data with theoretical calculations indicates that the antiferromagnetic coupling in the Cu system is greater than 45K: the complex shows a single magnetization plateau up to 60T at about 1/3 of the expected saturation. As for the Fe compound, several clear magnetization steps are observed in pulsed field, hinting for a coupling constant of about 10K. Slow dynamic spin fluctuations are observed in mössbauer spectra and in the µSR measurements down to millikelvin temperatures.