Berlin 2005 – wissenschaftliches Programm

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MA: Magnetismus

MA 10: FV-internes Symposium "Molecular Magnetism" (Organizer: H.J. Krüger)

MA 10.3: Hauptvortrag

Samstag, 5. März 2005, 10:00–10:30, TU H1012

Frustration effects in magnetic molecules — •Jürgen Schnack — Universität Osnabrück, Fachbereich Physik, D-49069 Osnabrück, Germany

Besides being a fascinating class of new materials, magnetic molecules provide the opportunity to study concepts of condensed matter physics in zero dimensions. This contribution will exemplify the impact of molecular magnetism on concepts of frustrated spin systems [1].

We will discuss spin rings and the unexpected rules that govern their low-energy behaviour. Rotational bands, which are experimentally observed in various molecular magnets, provide a useful, simplified framework for characterizing the energy spectrum, but there are also deviations thereof with far-reaching consequences. It will be explained in this context what localized independent magnons are and how they lead to giant magnetization jumps, a new macroscopic quantum effect [2]. In addition, frustration-induced plateaus of the magnetization and related susceptibility minima can be observed in magnetic molecules [3] as well as metamagnetic transitions. Finally, it is demonstrated that magnetic molecules could give rise to an enhanced magnetocaloric effect.

[1] J. Schnack, Molecular Magnetism, in Quantum Magnetism, Lecture Notes in Physics 645, Springer, Berlin, Heidelberg (2004) 155-194

[2] J. Schulenburg, A. Honecker, J. Schnack, J. Richter, H.-J. Schmidt, Macroscopic magnetization jumps due to independent magnons in frustrated quantum spin lattices, Phys. Rev. Lett. 88 (2002) 167207

[3] C. Schröder et al., Competing Spin Phases in Geometrically Frustrated Magnetic Molecules, Phys. Rev. Lett., submitted