  The electric-field control of magnetism is a highly promising and potentially
effective approach for achieving energy-efficient applications. In recent
times, there has been significant interest in the magneto-ionic effect in
synthetic antiferromagnets, primarily due to its strong potential in the
realization of high-density storage devices with ultra-low power consumption.
However, the underlying mechanism responsible for the magneto-ionic effect on
the interlayer exchange coupling (IEC) remains elusive. In this study, we have
successfully identified that the magneto-ionic control of the properties of the
top ferromagnetic layer of the synthetic antiferromagnet (SyAFM), which is in
contact with the high ion mobility oxide, plays a pivotal role in driving the
observed gate-induced changes to the IEC. Our findings provide crucial insights
into the intricate interplay between stack structure and magnetoionic-field
effect on magnetic properties in synthetic antiferromagnetic thin film systems.
