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Phys. Rev. B 74, 094434 (2006) [9 pages]

Neutron scattering from a coordination polymer quantum paramagnet

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T. Hong1, M. Kenzelmann1,2, M. M. Turnbull3, C. P. Landee3, B. D. Lewis3, K. P. Schmidt4, G. S. Uhrig5, Y. Qiu2,6, C. Broholm1,2, and D. Reich1
1Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
2National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
3Carlson School of Chemistry and Department of Physics, Clark University, Worcester, Massachusetts 01610, USA
4Institute of Theoretical Physics, École Polytechnique Fédérale de Lausanne, CH 1015 Lausanne, Switzerland
5Theoretische Physik, FR 7.1, Gebäude 38, Universität des Saarlandes, 66123 Saarbrücken, Germany
6Department of Materials and Engineering, University of Maryland, College Park, Maryland 20742, USA

Received 21 March 2006; revised 19 May 2006; published 29 September 2006

Inelastic neutron scattering measurements are reported for a powder sample of the spin-1∕2 quantum paramagnet Cu(quinoxaline)Br2. Magnetic neutron scattering is identified above an energy gap of 1.9 meV. Analysis of the sharp spectral maximum at the onset indicates that the material is magnetically quasi-one-dimensional. Consideration of the wave vector dependence of the scattering and polymeric structure further identifies the material as a two-legged spin-1∕2 ladder. Detailed comparisons of the data to various models of magnetism in this material based on the single-mode approximation and the continuous unitary transformation are presented. The latter theory provides an excellent account of the data with leg exchange J‖=2.0 meV and rung exchange J⊥=3.3 meV.

© 2006 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.74.094434
DOI:
10.1103/PhysRevB.74.094434
PACS:
75.10.Jm
 
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