A hybrid magnetic random-access memory using spin-orbit torque and multiferroics

Spin-orbit torque (SOT) is an energy efficient method to control magnetization with magnetic memory applications. However, using SOT to switch memory bits with perpendicular magnetic anisotropy (PMA) is still a challenge. Here we present a new strain-mediated SOT switching mechanism. The strain induced magnetoelastic anisotropy in the multiferroic heterostructure breaks lateral symmetry of SOT device thus produces field-free deterministic perpendicular switching. A finite element model and a macrospin model are used to numerically simulate the switching mechanism. Space inversion transformation is performed to show the symmetry breaking of strain-mediated SOT system. A relatively small voltage (±0.5V) combined with a modest current (3.5×10⁷ A/cm²) produces 180° perpendicular magnetization reversal. The switching direction (‘up’ or ‘down’) is dictated by the voltage polarity (positive or negative) applied to piezoelectric layer in the multiferroic heterostructure. The switching is fast (up to 10GHz) and does not require precisely timed voltage or current pulses. Based on the strain-mediated SOT control mechanism, a new random-access memory system is designed with high storage density and high scalability.