Interfacial Control via Reversible Ionic Motion in Battery-Like Magnetic Tunnel Junctions

Electrical control on interfaces is one of the key approaches to harvest advanced functionalities in modern electronic devices. In this work, it is proposed and demonstrated that a “battery-like” tunnel junction structure can be embedded with added control and functionalities via reversible lithium-ion motion. In a model system of FeCo/FeCoOx/LiF/FeCo magnetic tunnel junctions, the ultrathin LiF barrier makes strong electric fields possible under moderate applied voltages, and can therefore electrically drive reversible lithium-ion migration within the barrier. The ion motion subsequently leads to reversible interfacial modifications that generates over a thousand percent resistance change across the devices. Meanwhile, sizable tunneling magnetoresistance persists and even reverses the sign of spin polarization as a function of the interfacial control. The devices are therefore responsive to both electric and magnetic field manipulations, giving rise to diverse and nonvolatile functionalities.