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Prog. Theor. Phys. Supplement No.145 (2002) pp. 43-51

[ Full Text PDF : FREE ACCESS (118K) ]

Dynamics, Selection Rules and Dzyaloshinsky-Moriya Interactions in Strongly Frustrated Magnets

Olivier Cépas,1,2 Toru Sakai3 and Timothy Ziman1,*,**

1Institut Laue Langevin, B. P. 156, 38042 Grenoble, France
2Department of Physics, University of Queensland, QLD 4072 Australia
3Tokyo Metropolitan Institute of Technology, Asahigaoka, Hino 191-0065, Japan

(Received December 18, 2001)

Abstract:

Anisotropic spin-spin interactions of the symmetry described by Dzyaloshinsky and Moriya are generally considered weak, as they depend on the spin-orbit couplings. In frustrated spin systems with singlet ground states they can, however, have rather strong effects. We discuss recent results related to two gapped spin systems: CuGeO3 and SrCu2(BO3)2 in particular. In the first compound the Dzyaloshinsky-Moriya interactions effectively lower the symmetry of the magnetic unit cell and this leads to doubling of the low frequency mode. In the second case, the Dzyaloshinsky-Moriya interactions also split the lowest magnon mode linearly in the spin-orbit coupling. In addition, the relatively weak Dzyaloshinsky-Moriya interactions can dominate the dispersion.
Consideration of the selection rules for optical transitions show that while the Dzyaloshinsky-Moriya interactions can explain much of the dynamics, they do not explain the observed transition amplitudes. This leads to a review of recent calculations of anisotropic spin-phonon couplings. We discuss how this leads to a novel mechanism to explain the ESR intensities in the spin gap systems discussed. Selection rules for this novel mechanism involving coupling to the electric field of the resonant probe are discussed and relation to polarised neutron experiments briefly mentioned.


URL : http://ptp.ipap.jp/link?PTPS/145/43/
DOI : 10.1143/PTPS.145.43


*Also at CNRS, LPM2C, UMR 5493, Grenoble, France.
**E-mail: cepas@physics.uq.edu.au, tsakai@cc.tmit.ac.jp, ziman@ill.fr

[ Full Text PDF : FREE ACCESS (118K) ] Citation:

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Citing Article(s) :

  1. Journal of the Physical Society of Japan 72 (2003) pp. 3243-3253 :
    ESR Study on the Excited State Energy Spectrum of SrCu2(BO3)2 –A Central Role of Multiple-Triplet Bound States–
    Hiroyuki Nojiri, Hiroshi Kageyama, Yutaka Ueda and Mitsuhiro Motokawa
  2. Journal of the Physical Society of Japan 77 (2008) 074712 (13 pages) :
    Theory of Magnetic Excitations and Electron Spin Resonance for Anisotropic Spin Dimer Systems
    Masashige Matsumoto, Takayuki Shoji, and Mikito Koga

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