Significant Strain‐Induced Orbital Reconstruction and Strong Interfacial Magnetism in TiNi(Nb)/Ferromagnet/Oxide Heterostructures via Oxygen Manipulation

Dynamical manipulation of oxygen ion (O2−) at metal/oxide heterointerfaces is widely demonstrated to tailor numerous physical and chemical properties and facilitate creating novel functionalities significantly. The traditional works mainly focus on electric control of O2− dynamical behavior and related interface characteristics. Here, an alternative strategy is reported to modulate O2− transport and interfacial magnetism via a significant strain induced by shape memory effect, which is different from the conventional magnetoelastic coupling mechanism. By driving the martensite to austenite transition in TiNi(Nb) shape memory alloy substrates, a significant and tunable strain is exerted on Pt/Co/MgO heterostructure, which promotes interfacial O2− migration in a nonvolatile manner. The O2− migration induces an orbital reconstruction of Co to tune the orbital magnetism noticeably, which strengthens the interfacial magnetic anisotropy energy by two times to a striking value of 0.95 erg cm−2. Besides, the overall magnetic anisotropy is broadly tunable from in‐plane to perpendicular direction by an elaborate strain engineering with changing Co thickness. This work develops a nonelectrical oxygen manipulation for tailoring ion‐controlled interfacial properties universally and also clarifies the magnetoionic coupling origin for enriching the oxygen‐related orbital physics and functional device applications. This work develops a nonelectrical strategy of oxygen manipulation at the metal/oxide interfaces by using the significant strain from a shape memory alloy substrate. A prominent orbital reconstruction is observed by the strain‐induced O2− migration at Co/MgO interface, which strengthens interfacial magnetic anisotropy energy by two times. Besides, overall magnetic anisotropy is broadly tunable from in‐plane to perpendicular direction.