Oxygen Vacancy Engineering for Highly Tunable Ferromagnetic Properties: A Case of SrRuO₃ Ultrathin Film with a SrTiO₃ Capping Layer

Oxide heterostructures have great potential for spintronics applications due to their well-defined heterointerfaces and vast functionalities. To integrate such compelling features into practical spintronics devices, effective control of the magnetic switching behavior is key. Here, continuous control of the magnetic coercive field in SrTiO₃/SrRuO₃ ultrathin heterostructures is achieved by oxygen vacancy (V_O) engineering. Pulsed laser deposition of an oxygen-deficient SrTiO₃ capping layer can trigger V_O migration into the SrRuO₃ layer while avoiding the formation of Ru vacancies. Moreover, by varying the thickness and growth conditions of the SrTiO₃ capping layer, the value of the coercive field (H_C) in the ferromagnetic SrRuO₃ layer can be continuously tuned. The maximum enhancement of H_C at 5 K is 3.2 T. Such a wide-range tunability of H_C may originate from a V_O-induced enhancement of perpendicular magnetic anisotropy and domain wall pinning. This study offers effective approaches for controlling physical properties of oxide heterostructures via V_O engineering, which may facilitate the development of oxide-based functional devices.