The role of defects in the magneto-ionic control of exchange-bias thin films

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The exchange bias is an important interface-related effect in modern thin-film magnetism. It offers an elegant way to control the remnant magnetization direction of ferromagnetic layers in magnetic memories, sensors, spintronics and magnetophoretic devices. Especially, artificial magnetic domain patterns with tailored stray field landscapes can be created in in-plane exchange bias films by the controlled introduction of defects and energy via light-ion bombardment.Thus, light ion bombardment presents a versatile method to modify magnetic anisotropies, but, due to the influence of accumulating defects in successive bombardment steps a reversible modification of anisotropies cannot be achieved by this technology. The reversible electric control of interface-related magnetic properties by the insertion and removal of ions in magnetic layers via an electrochemical approach (magneto-ionic control) is an emerging concept. However, kinetics are limited by the ion transport in the material. Even though defects are expected to play a pivotal beneficial role as ion transport paths, the impact of defects on the magneto-ionic switching has not been studied systematically yet. In the proposed project, the combination of defect-modified exchange bias films and magneto-ionic interface control will be studied as a novel approach towards (i) a reversible programming of artificial magnetic domains in exchange bias systems and (ii) an increase in the switching speed and efficiency of magneto-ionic switching. The fundamental understanding of the role of defects for magneto-ionic switching will open up new avenues toward the tuning of functional interfaces in general. For instance, the gained knowledge will also pave a way to new design options for other interface-related magnetic phenomena such as the Dzyaloshinskii–Moriya-interaction or spin orbit torques.