Emerging Magnetoresistive Memories

Abstract

Nonvolatile CMOS-compatible spin-transfer torque (STT) and spin-orbit torque (SOT) magnetoresistive random access memories (MRAMs) exhibit high speed, endurance, and long retention when compared to competing technologies. These advanced devices are composed of multiple magnetic layers, which are separated by tunnel barriers and non-magnetic metalic spacers. To effectively model magnetization dynamics in such complex structures, we employ a coupled spin and charge transport approach accurately capturing spin accumulation and the torques acting on ferromagnetic layers. We apply appropriate boundary conditions at the interfaces to evaluate spin and charge transport in metallic spin valves and magnetic tunnel junctions. Our approach has demonstrated versatility in several areas, including the accurate evaluation of the operation of ultra-fast multilayer STT-MRAM, achieving magnetic field-free switching in SOT-MRAM with a heavy metal/ferromagnetic stack, and managing magnetization in the strained noncollinear antiferromagnet Mn3Sn. By integrating an Mn3Sn layer with a ferromagnetic layer, we enable electrical control over magnetization, thus creating opportunities for future field-free SOT-MRAM devices.