  The theoretical understanding of time-dependence in magnetic quantum systems
is of great importance in particular for cases where a unitary time evolution
is accompanied by relaxation processes. A key example is given by the dynamics
of single-molecule magnets where quantum tunneling of the magnetization
competes with thermal relaxation over the anisotropy barrier. In this article
we investigate how good a Lindblad approach describes the relaxation in giant
spin models and how the result depends on the employed operator that transmits
the action of the thermal bath.
