  A macroscopic effect can be induced by a local non-Hermitian term in a
many-body system, when it manifests simultaneously level coalescence of a full
real degeneracy spectrum, leading to exceptional spectrum. In this paper, we
propose a family of systems that support such an intriguing property. It is
generally consisted of two arbitrary identical Hermitian sub-lattices in
association with unidirectional couplings between them. We show exactly that
all single-particle eigenstates coalesce in pairs even only single
unidirectional coupling appears. It means that all possible initial states obey
the exceptional dynamics, resulting in some macroscopic phenomena, which never
appears in a Hermitian system. As an application, we study the dynamic
magnetization induced by complex fields in an itinerant electron system. It
shows that an initial saturated ferromagnetic state at half-filling can be
driven into its opposite state according to the dynamics of high-order
exceptional point. Any Hermitian quench term cannot realize a steady opposite
saturated ferromagnetic state. Numerical simulations for the dynamical
processes of magnetization are performed for several representative situations,
including lattice dimensions, global random and local impurity distributions.
It shows that the dynamic magnetization processes exhibit universal behavior.
