Lithium-Ion Migration-Induced Magnetic Anisotropy Transition in CoNi Thin Films

Voltage control of magnetic anisotropy in nanoscale heterostructures plays a pivotal role in the design and realization of magnetic random-access memories. To achieve low-voltage operation with high reversibility, we introduce an ion-conducting TiO₂ layer capable of storing lithium ions atop a Ta/Pt/CoNi heterostructure. During the discharging process, lithium ions migrate into the TiO₂ layer. The resulting interfacial electric field between TiO₂ and CoNi induces a reversible evolution of magnetic anisotropy from the out-of-plane direction toward the in-plane direction. Within a voltage window of 1.5 V (from 3.0 V to 1.5 V), both remanent magnetization and coercivity are suppressed to zero. Furthermore, consecutive charge-discharge cycles indicate the reversibility in the modulation of remanent magnetization and coercivity. These findings highlight that ion migration at the magnetic interface enables efficient and reversible control of magnetic anisotropy, opening new opportunities for the development of low-power spintronic devices.