  Electric field control of the exchange bias effect across
ferromagnet/antiferromagnet (FM/AF) interfaces has offered exciting potentials
for low-energy-dissipation spintronics. In particular, the solid state
magneto-ionic means is highly appealing as it may allow reconfigurable
electronics by transforming the all-important FM/AF interfaces through ionic
migration. In this work, we demonstrate an approach that combines the
chemically induced magneto-ionic effect with the electric field driving of
nitrogen in the Ta/Co$_{0.7}$Fe$_{0.3}$/MnN/Ta structure to electrically
manipulate exchange bias. Upon field-cooling the heterostructure, ionic
diffusion of nitrogen from MnN into the Ta layers occurs. A significant
exchange bias of 618 Oe at 300 K and 1484 Oe at 10 K is observed, which can be
further enhanced after a voltage conditioning by 5% and 19%, respectively. This
enhancement can be reversed by voltage conditioning with an opposite polarity.
Nitrogen migration within the MnN layer and into the Ta capping layer cause the
enhancement in exchange bias, which is observed in polarized neutron
reflectometry studies. These results demonstrate an effective nitrogen-ion
based magneto-ionic manipulation of exchange bias in solid-state devices.
