Ultrafast and Directional Magnetization Control via Voltage-Controlled Exchange Coupling

Abstract: Ultrafast and energy-efficient electrically controlled magnetization switching is critical for next-generation spintronic devices. Voltage-driven switching offers an alternative to current-driven methods, significantly improving energy efficiency. Although voltage-controlled exchange coupling (VCEC) has been proposed to switch magnetic states, its ultrafast response has not been experimentally verified. Here, we demonstrate that VCEC induces a directional exchange field that persists under nanosecond voltage pulses in a perpendicular magnetic tunnel junction (pMTJ) with an exchange-coupled free layer. This establishes that VCEC can operate on ultrafast timescales with deterministic control over the switching polarity. The magnetization reversal is primarily assisted by voltage-induced magnetic anisotropy (VCMA), which transiently lowers the energy barrier. This combination enables magnetization switching within 87.5 ps with a 50% switching probability. The fast switching is attributed to enhanced magnetic relaxation of the free layer, facilitated by the exchange-coupled structure, which accelerates voltage-driven magnetization switching. These findings reveal that purely voltage-driven switching is viable for fast, bidirectional magnetization switching for future spintronic logic and memory technologies.