P.H. Plakhty¹, Th. Brückel, W. Schweika, J. Kulda², S. Gavrilov¹, D. Visser^3,4,5
1Petersburg Nuclear Physics Institut
²ILL Grenoble
³Department of Physics, University of Warvick
⁴ISIS Facility, Rutherford Appleton Laboratory
⁵IRU, Tu Delft

The critical exponent for the average chirality, ßc = 0.79(3), and the chiral susceptibility, rc = 0.79(5), are determined for the spin-ordering transition in helimagnet Ho. The rc agrees with the Monte Carlo va1ue for the XY chiral universality class, while the ßc is substantially higher than a predicted value. It is shown that ßc > 2ß = 0.67(1), which indicates that chirality is an additional component of the order parameter, but not simply a vector product of two spins.