Abstract
The results of a quasielastic neutron scattering experiment on CsNiF3 around TN are reported and discussed. At TN the ferromagnetic chains, which determine the magnetic behaviour for T > TN , order anti-ferromagnetically in a collinear arrangement. The critical properties are expected to show the usual three-dimensional behaviour. By fitting the convolution of a Lorent-zian and a Gaussian line to the experimental data, the critical indices β, γ ν, could be determined with TN , = 2.664 K. β was found to be The indices ν γ, for T > TN were found to be different in different ε-ranges: This corresponds to a crossover from MFA to x-y critical behavior when approaching TN , from above.