Voltage-controlled MRAM for working memory: Perspectives and challenges

Magnetic random access memory (MRAM) has been widely studied for future nonvolatile working memory candidate. However, the mainstream current (spin transfer torque, STT or spin Hall effect, SHE) driven MRAMs (STT-MRAM or SHE-MRAM) face intrinsic problems in terms of high write power and long latency, significantly limiting the applications for low-power and high-speed working memories. The recently-developed new-generation MRAM, named VCMA-MRAM, which exploits the voltage-controlled magnetic anisotropy (VCMA) effect to write (or assist to write) data information into magnetic tunnel junctions (MTJs), holds the promise to efficiently overcome these problems. Despite the impressive possibility of improving write power and speed, this technology, however, is currently under intensive research and development (R&D), and some challenges still await answers. In this paper, we investigate the perspectives and challenges of VCMA-MRAM for working memories from a cross-layer (device/circuit/architecture) design point of view. We demonstrate that VCMA-MRAM outperforms STT-MRAM and SHE-MRAM in terms of area, speed, energy consumption and instruction-per-cycle (IPC) performance, benefiting from the low-power and high-speed VCMA-driven data writing mechanism. On the other hand, challenges in terms of device fabrication and circuit design should be efficiently addressed before practical applications.