  In discrete energy structure of nanoscale magnets, nonadiabatic transitions
at avoided level crossings lead to fundamental processes of dynamics of
magnetizations. The thermal environment causes dissipative effects on these
processes. In this paper we review the features of the nonadiabatic transition
and the influence of the thermal environment. In particular we discuss the
temperature independent stepwise structure of magnetization at very low
temperatures (deceptive nonadiabatic transition), the alternate enhancement of
relaxation in the sequence of resonant tunneling points (parity effects), and
processes caused by combinations of nonadiabatic transitions and disturbance
due to external noises.
