  The theory of spin superradiance, developed earlier for nuclear magnets, is
generalized to a wider class of spin systems, such as granular magnets and
molecular magnets. The latter may possess strong single-site magnetocrystalline
anisotropy, whose role in nonlinear spin dynamics is analysed. Transient as
well as pulsing superradiant regimes are described. These coherent regimes may
be employed in the operation of spin masers.
