Strain-Mediated Spin-Orbit-Torque Switching for Magnetic Memory

Spin-orbit torque (SOT) switching is an energy-efficient method to control magnetization in magnetic memory devices. However, deterministically switching perpendicular memory bits usually requires the application of an additional bias field to break lateral symmetry. Here we present a field-free deterministic perpendicular switching approach using a strain-mediated SOT switching method. The strain-induced magnetoelastic anisotropy breaks the lateral symmetry, and the resulting symmetry breaking is controllable. A finite-element model and a macrospin model are used to numerically simulate the strain-mediated SOT switching mechanism. The results show that a relatively small voltage (+/- 0.5 V) along with a current (5 x 10(7) A/cm(2)) can produce a 180 degrees perpendicular magnetization reversal. The switching direction (up or down) is dictated by the voltage polarity (positive or negative) applied to the piezoelectric layer in the magnetoelastic/heavy metal/piezoelectric heterostructure. The switching speed can be as fast as 10 GHz. More importantly, this control mechanism can be potentially implemented in a magnetic random-access memory system with a small footprint, high endurance, and high tunnel magnetoresistance readout ratio.