Europhys. Lett.
Volume 66, Number 3, May 2004
Page(s) 423 - 429
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 01 April 2004
Europhys. Lett., 66 (3) , pp. 423-429 (2004)
DOI: 10.1209/epl/i2004-10008-x

Mechanism of ground-state selection in the frustrated molecular spin cluster $\chem{V_{15}}$

G. Chaboussant1, S. T. Ochsenbein1, A. Sieber1, H.-U. Güdel1, H. Mutka2, A. Müller3 and B. Barbara4

1  Department of Chemistry, University of Bern - CH-3000 Bern 9, Switzerland
2  Institut Laue-Langevin - BP 156, 38042 Grenoble, France
3  Department of Chemistry, University of Bielefeld - 33501 Bielefeld, Germany
4  Laboratoire de Magnétisme Louis Néel, CNRS - BP 166, 38042 Grenoble, France

(Received 5 January 2004; accepted in final form 23 February 2004)

We report an inelastic neutron scattering (INS) study under a magnetic field on the frustrated molecular spin cluster V15. Several field-dependent transitions are observed and provide a comprehensive understanding of the low-energy quantum spin states. The energy gap $2\Delta_0\approx 27(3)$ $\un{\mu eV}$ between the two lowest S=1/2 Kramers doublets is unambiguously attributed to a symmetry lowering of the cluster. The INS data are mapped onto an S=1/2 Antiferromagnetic Heisenberg triangle with scalene distortion. A quantitative description of the wave function mixing within the ground state is derived.

75.30.Et - Exchange and superexchange interactions.
75.50.Xx - Molecular magnets.
78.70.Nx - Neutron inelastic scattering.

© EDP Sciences 2004