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Regensburg 2000 – scientific programme

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AM: Magnetismus

AM 6: Elektronentheorie und Modelle geordneter Spinstrukturen

AM 6.4: Talk

Monday, March 27, 2000, 14:45–15:00, H22

Investigation of small classical and quantum Heisenberg-spin-systems — •D. Mentrup1, J. Schnack1, and Marshall Luban21Universität Osnabrück, Fachbereich Physik, Barbarastr. 7, 49069 Osnabrück — 2Ames Laboratory & Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA

There is a growing interest in the magnetic properties of synthesized molecules containing relatively small numbers of paramagnetic ions. As their magnetic interaction seems to be well described by the Heisenberg model, we have investigated properties of classical and quantum Heisenberg dimers and trimers, focussing on thermodynamic properties and time-dependent correlation functions. Exact analytical calculations for the density of states and for time correlation functions point the way in which the quantum result reaches the classical limit for large spin quantum numbers.
Moreover, we have carried out quantum calculations for the molecular magnets V6 (spin-1/2-triangle) and Cr4 (spin-3/2-tetrahedron) that allow numerous comparisons with experimental data. The results for the magnetization, susceptibility, and spin-lattice relaxation time strikingly justify the use of the Heisenberg model.

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