Lithium-Ionic Control of Magnetism Through Spin Capacitance and Conversion

Magnetoelectric (ME) coupling has gradually developed into one of the core means of advancing ultralow-power memory, logic and sensor technologies. Among various strategies, magneto-ionic control of magnetism based on mechanism such as redox, intercalation/deintercalation, and charge accumulation can be achieved in ion battery or capacitor systems. In this work, we demonstrate a ME effect originating from the spin capacitance, combining the advantages of intercalation batteries and supercapacitors. A giant, fast and reversible modulation on the saturation magnetization of ferromagnetic Fe is achieved by lithium ions motion across the Fe/Li2O interface at no more than 1 V. Furthermore, the magnetic evolution driven by the conversion reaction between FeO and Fe over a larger voltage range demonstrates ferromagnetic ordering of the FeO surface. These findings not only open new perspectives for developing high-performance magneto-ionic devices, but also are crucial to designing spintronic devices composed of iron and oxide multilayer structures.