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

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

Abstract

The temperature behaviour of the polarisation-dependent part of the differential cross-section of inelastic neutron scattering is investigated for the triangular-lattice antiferromagnet in the critical region above T_N with the external magnetic field , applied along the hexagonal axis c, or the scattering vector Q(1/3 1/3 1). In the range of reduced temperature 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 . This is the first chiral critical exponent determined experimentally, which gives a direct proof of the chiral universality.