Modeling Advanced Magnetoresistive Memories

Abstract

Nonvolatile CMOS-compatible spin-transfer torque (STT) and spin-orbit torque (SOT) magnetoresistive random access memories (MRAMs) possess high speed and endurance as well as long retention compared to their competitors. Advanced MRAM devices are composed of multiple magnetic layers separated by tunnel barriers and nonmagnetic metallic spacers. To efficiently model magnetization dynamics in complex, multilayered structures, we use a coupled spin and charge transport approach, which accurately captures the spin accumulation and the torques acting on ferromagnetic layers. Appropriate boundary conditions at the interfaces are applied to determine the spin and charge transport in metallic spin valves and magnetic tunnel junctions. We demonstrate the versatility of our approach by applying it to evaluate operation in ultra-fast multilayer STT-MRAM, efficient magnetic fieldfree switching in SOT-MRAM with a heavy metal/ferromagnetic SOT stack, as well as a magnetization control in strained noncollinear antiferromagnet Mn<inf>3</inf> Sn. By combining an Mn<inf>3</inf> Sn layer with a ferromagnetic layer, electrical control over magnetization is achieved, opening perspectives for future field-free SOT-MRAM devices.