Gate-induced switching of perpendicular exchange bias with very low coercivity in Pt/Co/Ir/Cr₂O₃/Pt epitaxial film

We investigate magnetoelectric switching of perpendicular exchange bias with very low coercivity in a Pt/Co/Ir/Cr₂O₃/Pt epitaxial film. We also optimize the suitable Ir spacer thickness so that the film exhibits the perpendicular exchange bias greater than the coercivity up to the vicinity of the Néel temperature. Main impact of the Ir spacer layer is the significant reduction of coercivity less than 0.5 mT in maintaining both the perpendicular magnetic anisotropy and the perpendicular exchange bias. For the suitable structure, the perpendicular exchange bias was isothermally switched by the gate voltage in combination with the magnetic field. Analysis of the hysteresis of the exchange bias field as a function of the gate voltage suggested that the magnetoelectric coefficient was comparable to the reported value. This implies that the Ir layer does not degrade the efficiency to transfer the magnetoelectrically controlled antiferromagnetic order parameter to the ferromagnetic Pt/Co/Ir trilayer.