Critical dynamics and statics of uniaxial dipolar magnets

The critical behaviour of uniaxial ferromagnets is studied by an anisotropic renormalization transformation. For dimensionalityd smaller than the critical dimensionalityd_c(d_u), which depends on the dimensionality of the uniaxial directiond_u, the critical exponents are computed by the-expansion. The critical dynamics is based on a timedependent Ginzburg Landau model, for a non-conserved and for a conserved order parameter. For the experimentally relevant cased=3 andd_u=1 the logarithmic corrections in the frequency dependent susceptibility are computed.Work supported by the Fonds zur Förderung der wissenschaftlichen Forschung