The Effect of Material Defects on Magneto-Elastic Switching

Past experiments have shown that magneto-elastic switching phenomenon is extremely energy-efficient but error-prone. We have studied the effect of material defects (voids, thickness variations, etc.) on the switching probability of elliptical magnetostrictive nanomagnets subjected to uniaxial strain using micromagnetic simulations in the presence of thermal noise. Defects drastically increase the switching error rate. Curiously, there is a critical value of stress that results in the minimum error rate for both defective and defect-free nanomagnets. The critical stress is much higher for defective nanomagnets. Another interesting observation was that if the nanomagnet’s thickness is different in two different halves, then stable magnetization states are spawned along the nanomagnet’s hard axis. Above a certain thickness variation, the magnetization tends to get pinned along the hard axis when the nanomagnet is stressed and remains stuck there even after stress removal. These unexpected observations reveal some of the complexities associated with magneto-elastic switching, with important ramifications for practical applications of straintronics.