  We find that a new type of non-reciprocal modes exist at an interface between
two \emph{parity-time} ($\mathcal{PT}$) symmetric magnetic domains (MDs) near
the frequency of zero effective permeability. The new mode is non-propagating
and purely magnetic when the two MDs are semi-infinite while it becomes
propagating in the finite case. In particular, two pronounced nonreciprocal
responses could be observed via the excitation of this mode: one-way optical
tunneling for oblique incidence and unidirectional beam shift at normal
incidence. When the two MDs system becomes finite in size, it is found that
perfect-transmission mode could be achieved if $\mathcal{PT}$-symmetry is
maintained. The unique properties of such an unusual mode are investigated by
analytical modal calculation as well as numerical simulations. The results
suggest a new approach to the design of compact optical isolator.
