Chiral criticality in helimagnet Ho studied by polarized neutron scattering

Abstract

The critical exponents for the average chirality, ${\ensuremath{\beta}}_{c}=0.90(3),$ and the chiral susceptibility, ${\ensuremath{\gamma}}_{c}=0.68(6),$ are determined for the spin-ordering transition in helimagnet Ho. The ${\ensuremath{\beta}}_{c}$ is extraordinarily large and twice higher than the predicted value for the chiral universality class, while the ${\ensuremath{\gamma}}_{c}$ is in agreement with this scenario. The staggered magnetization critical exponent is determined to be \ensuremath{\beta}=0.38(1). The difference ${\ensuremath{\beta}}_{c}\ensuremath{-}2\ensuremath{\beta}=0.137(36)$ suggests that chirality is a component of the order parameter independent of the staggered magnetization. The chiral-ordering transition and the N\'eel temperature coincide with a relative precision of ${10}^{\ensuremath{-}4}.$