Chiral critical behaviour in CsNiCl 3

Abstract

Neutron diffraction experiments have been performed on the hexagonal antiferromagnet CsNiCl 3 in order to determine the critical exponent β along the phase boundary between paramagnetic and spin-flop phase. At field strengths far above the spin-flop field our data are consistent with predictions for the n = 2 chiral universality class, β = 0.25. Close to the spin-flop transition, where the weak Ising anisotropy present in CsNiCl 3 is cancelled by the magnetic field, good agreement is achieved with the critical exponent of the n = 3 chiral universality class.