Abstract
Residual magnetic frustration in the multiferroic LuMnO3 may be key towards understanding magneto-elastic coupling in hexagonal manganites. Critical magnetic scattering present well above the magnetic ordering temperature T-N persists below, as observed by inelastic neutron scattering. The magnetic fluctuations are confined in two dimensions implied by the characteristic wavevector dependence of the magnetic structure factor that changes from symmetric to asymmetric across T-N. The low dimensionality of the magnetic structure is also evident in the temperature dependence of the commensurate antiferromagnetic intensity which follows a mean field exponent of beta similar to 0.2.