Europhys. Lett.
Volume 48, Number 2, October 1999
Page(s) 215 - 220
Section Condensed matter: electronic structure, electrical, magnetic and optical properties
Published online 01 September 2002
DOI: 10.1209/epl/i1999-00468-4

Europhys. Lett, 48 (2), pp. 215-220 (1999)

Inelastic polarised neutron scattering in the triangular-lattice antiferromagnet $\rm CsMnBr_3$: An experimental proof of the chiral universality

V. P. Plakhty 1, S. V. Maleyev 1, J. Kulda 2, J. Wosnitza 3
D. Visser 4 and E. Moskvin 1

1 Petersburg Nuclear Physics Institute, RAS, Gatchina - St. Petersburg, 188350 Russia
2 Institut Laue-Langevin - BP 15, 38042 Grenoble Cedex 9, France
3 Physikalisches Institut, Universität Karlsruhe - 76128 Karlsruhe, Germany
4 Department of Physics, University of Warwick - Coventry CV4 7AL, UK

(received 11 June 1999; accepted 30 August 1999)

PACS. 75.25${\rm +z}$ - Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source X-ray scattering, etc.).
PACS. 75.40Gb - Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.).
PACS. 75.40${\rm -s}$ - Critical-point effects, specific heat, short-range order.


The temperature behaviour of the polarisation-dependent part of the differential cross-section of inelastic neutron scattering is investigated for the triangular-lattice antiferromagnet $\rm CsMnBr_3$ in the critical region above $T_{\rm N}$ with the external magnetic field $H = 4\;{\rm T}$, applied along the hexagonal axis c, or the scattering vector Q(1/3 1/3 1). In the range of reduced temperature $\tau \gt 0.1$ restricted by the resolution, this part of the cross-section, which is determined by the projection of a chiral fluctuation on the field-induced magnetisation, follows a power law of reduced temperature with the critical chiral crossover exponent $\phi_{\rm C} = 1.29(7)$. This is the first chiral critical exponent determined experimentally, which gives a direct proof of the chiral universality.


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