SFB 668


SFB 668

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23.2.2006, 15:30
Jungiusstr. 9, Hörsaal III

SFB 668 - Kolloquium

Prof. Jürgen Schnack (Uni Osnabrück):

Frustration effects in magnetic molecules

Besides being a fascinating class of new materials, magnetic molecules provide the opportunity to study concepts of condensed matter physics in zero dimen-sions. This contribution will exemplify the impact of molecular magnetism on concepts of frustrated spin systems [1]. We will discuss rotational bands of energy eigenvalues, which are experimen-tally observed in various molecular magnets and 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 phase transitions [4]. 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, H. Nojiri, J. Schnack, P. Hage, M. Luban, P. Kögerler, Competing Spin Phases in Geometrically Frustrated Magnetic Molecules, Phys. Rev. Lett. 94 (2005) 017205
[4] C. Schröder, H.-J. Schmidt, J. Schnack, and M. Luban, Metamagnetic phase transition of the antiferromagnetic Heisenberg icosahedron, Phys. Rev. Lett. 94 (2005) 207203

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