Regensburg 2000 – wissenschaftliches Programm
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AM: Magnetismus
AM 6: Elektronentheorie und Modelle geordneter Spinstrukturen
AM 6.4: Vortrag
Montag, 27. März 2000, 14:45–15:00, H22
Investigation of small classical and quantum Heisenberg-spin-systems — •D. Mentrup1, J. Schnack1, and Marshall Luban2 — 1Universität 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.