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Dresden 2009 – scientific programme

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MA: Fachverband Magnetismus

MA 40: Poster II: Bio- and Molecular Magnetism (1-9); Magnetic Coupling Phenomena/Exchange Bias (10-15); Magnetic Particlicles and Clusters (16-29); Micro and Nanostructured Magnetic Materials (30-51); Multiferroics (52-64); Spin Injection in Heterostructures (65-67); Spin-Dyn./Spin-Torque (68-93); Spindependent Transport (94-108)

MA 40.8: Poster

Friday, March 27, 2009, 11:00–14:00, P1A

Investigation of Electronic Spin Dynamics in the Giant Keplerat Molecule Fe30Mo72 by 57Fe Moessbauer Spectroscopy and Magnetisation Measurements — •Til Dellmann1,2, F. Jochen Litterst1, H.-Henning Klauß2, Jürgen Schnack3, Bernd Büchner4, Anupama Parameswaran4, Rüdiger Klingeler4, and Achim Müller51IPKM TU Braunschweig — 2IFP TU Dresden — 3Fakultät für Physik, Uni Bielefeld — 4IFW Dresden — 5Anorganische Chemie I, Uni Bielefeld

In the frustrated polyoxomolybdate nanomolecule Fe30Mo72, 30 Fe(III) ions (S=5/2) are located on the vertices of an icosidodecahedron coupled via nearest neighbor antiferromagnetic interactions J0. However, recent ac suszeptibility measurements by Schröder et al. [1] show that the interactions are non-isotropic and can be described by a random distribution around J0.

We performed 57Fe Moessbauer spectroscopy on this system down to 2 K. Dynamic magnetic hyperfine spectra with magnetically inequivalent sites appear below 6 K. We conclude slow paramagnetic relaxation in agreement with dc magnetisation measurements. Furthermore, the magnetic field dependence at low temperatures (T=50mK) has been studied by ac susceptibility measurements. No magnetsation steps could be observed as predicted by the quantum rotational band model [2]. The implications of our results on this low temperature quantum model are being discussed on the poster.

[1] C. Schröder et al., Phys.Rev.B 77 (2008), 224409

[2] J. Schnack et al., Europhys. Lett., 56 (6), pp. 863-869 (2001)

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