Roles of magnetic coupling and spin-orbit torque in the electrical manipulation of exchange bias in a Pt/Co/IrMn heterostructure

Heavy-metal/ferromagnet/antiferromagnet heterostructures have attracted significant attention in manipulat-ing antiferromagnetic ordering electrically. We report electric control of the exchange bias field along both the out-of-plane and in-plane directions in Pt/Co/IrMn with assist magnetic fields. Experiments with different directions and amplitudes of the assist magnetic field show the role of magnetic coupling between ferromagnet and antiferromagnet spins. Furthermore, we find that the magnitude and direction of the exchange bias can be manipulated by the magnitude of the current pulse. The observed results can be explained based on a numerical macrospin model; the antiferromagnetic spins are excited and precessed from their ground state via the spin-orbit torque-driven oscillation and are reoriented, being mediated by magnetic coupling with the ferromagnet. Our results provide an approach to achieve electrical omnidirectional exchange bias manipulation and an understanding of the spin dynamics at the antiferromagnet-ferromagnet interface.