  We study the finite temperature antiferromagnetic phase of the ionic Hubbard
model in the strongly interacting limit using quantum Monte Carlo based
dynamical mean field theory. We find that the ionic potential plays a dual role
in determining the antiferromagnetic order. A small ionic potential (compared
to Hubbard repulsion) increases the super-exchange coupling in the projected
sector of the model, leading to an increase in the Neel temperature of the
system. A large ionic potential leads to resonance between projected
antiferromagnetically ordered configurations and density ordered configurations
with double occupancies, thereby killing antiferromagnetism in the system. This
novel way of degrading antiferromagnetism leads to spin polarization of the low
energy single particle density of states. The dynamic response of the system
thus mimics ferromagnetic behaviour, although the system is still an
antiferromagnet in terms of the static spin order.
