  Molecular spin crossover switches are the objects of intense theoretical and
experimental studies in recent years. This interest is due to the fact that
these systems allow one to control their spin state by applying an external
photo-, thermo-, piezo-, or magnetic stimuli. The greatest amount of research
is currently devoted to the study the effect of the photoexcitation on the
bi-stable states of spin crossover single molecular magnets (SMMs). The main
limitation of photo-induced bi-stable states is their short lifetime. In this
paper we present the results of a study of the spin dynamics of the CoOEP
molecule in the Low Spin (LS) state and the High Spin (HS) state induced by
applying the magnetic pulse of 36.8 T. We show that the spin switching in case
of the HS state of the CoOEP molecule is characterized by a long lifetime and
is dependent on the magnitude and duration of the applied field. Thus, after
applying an external stimuli the system in the LS state after the spin
switching reverts to its ground state, whereas the system in the HS state
remains in the excited state for a long time. We found that the temperature
dependency of magnetic susceptibility shows an abrupt thermal spin transition
between two spin states at 40K. The proposed here theoretical approach opens
the way to create modern devices for spintronics with the controllable spin
switching process.
