  We present dynamical properties of spin crossover compounds with
photomagnetization, proposing a new model in which the spin-crossover phenomena
and magnetic ordering are incorporated in a unified way. By using this model,
the novel characteristics observed in Prussian blue analogs are qualitatively
well reproduced. We investigate the time evolution of the magnetization and
high spin fraction taking into account multi-time scales in a master equation
approach for the magnetic relaxation, the lattice (electronic) relaxation, and
the photoexcitation process. In particular, processes with different
temperature cycles starting from the photoinduced saturated magnetic state are
studied including the effect of photoirradiation. In the temperature cycle in
the low temperature region where the high spin state has a strong
metastability, the magnetization almost exactly follows the quasi-static
process. On the other hand, when the temperature is raised above the region,
the dynamics of the spin state and the magnetization couple and exhibit various
types of dynamical cooperative phenomena under time-dependent control of
temperature and photoirradiation.
