  We consider Gaussian fluctuations about domain walls embedded in one- or
two-dimensional spin lattices. Analytic expressions for the free energy of one
domain wall are obtained. From these, the temperature dependence of
experimentally relevant spatial scales -- i.e., the correlation length for spin
chains and the size of magnetic domains for thin films magnetized out of plane
-- are deduced. Stability of chiral order inside domain walls against thermal
fluctuations is also discussed.
