Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 27: Bio- and Molecular Magnetism

MA 27.6: Vortrag

Donnerstag, 28. Februar 2008, 15:45–16:00, EB 202

Electronic Spin Dynamics and Static Order in Coupled Magnetic Keplerates Fe₃₀Mo₇₂ — •F.J. Litterst¹, H.-H. Klauss^1,2, T. Dellman^1,2, J. Schnack³, R. Klingeler⁴, and A. Müller⁵ — ¹IPKM, TU Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig — ²IFP, TU Dresden, Zellesche Weg 16, 01069 Dresden — ³Fakultät für Physik, Univ. Bielefeld, 33501 Bielefeld — ⁴IFW-Dresden, Helmholtzstr. 20, 01171 Dresden — ⁵Anorganische Chemie I, Univ. Bielefeld, 33501 Bielefeld

In the polyoxomolybdate nanomolecule Fe₃₀Mo₇₂ 30 S=5/2 FeIII ions are located on the vertices of an icosidodecahedron coupled via nearest-neighbor antiferromagnetic interactions J [1]. In the paramagnetic molecules the electronic ground state and excitations are governed by the strong magnetic frustration on the Kagomé-like surface [2]. A modified system with much stronger inter-molecular exchange interaction [3] shows several anomalies in the magnetic susceptibility below 5 K.

We performed ⁵⁷Fe-Mössbauer spectroscopy on the isolated and magnetically interacting molecules. Around 4.45 K (broad maximum in χ(T)) dynamic magnetic hyperfine spectra with magnetically inequivalent sites appear. Around 2.45 K a drop in χ(T) is accompanied by a slowing down of hyperfine dynamics and indicates antiferromagnetic order.

[1] A. Müller et al., Angew. Chem. Int. Ed. Engl. 38 (1999) 3238. [2] V.O. Garlea et al., Phys. Rev. B 73 (2006) 024414. [3] A. Müller et al., Angew. Chem. Int. Ed. Engl. 39 (2000) 1612.