Chiral fluctuations in MnSi above Tc

Abstract

Polarized neutrons are used to determine the antisymmetric part of the magnetic susceptibility in non-centrosymmetric MnSi. The paramagnetic fluctuations are found to be incommensurate with the chemical lattice and to have a chiral character. We argue that antisymmetric interactions must be taken into account to properly describe the critical dynamics in MnSi above T$_C$. The possibility of directly measuring the polarization dependent part of the dynamical susceptibility in a large class of compounds through polarised inelastic neutron-scattering is outlined as it can yield direct evidence for antisymmetric interactions like spin-orbit coupling in metals as well as in insulators.