Magnetoresistive Random Access Memory: Present and Future

TLDR

Magnetoresistive random access memory (MRAM) is regarded as a reliable persistent memory technology because of its long data retention and robust endurance. The article reviews current and future MRAM technologies, aiming to enable scaling to higher capacities. MRAM employs toggle mode writing of a balanced synthetic antiferromagnet free layer, and the review covers the evolution to spin‑transfer torque switching and emerging technologies. STT‑MRAM scaling to 1‑Gb devices in 2019, coupled with lower power, higher performance, and improved data integrity, meets the growing demands of data centers and IoT.

Abstract

Magnetoresistive random access memory (MRAM) is regarded as a reliable persistent memory technology because of its long data retention and robust endurance. Initial MRAM products utilized toggle mode writing of a balanced synthetic antiferromagnet (SAF) free layer to overcome problems with half-selected bits that challenged traditional Stoner-Wohlfarth switching. With the development of spin transfer torque (STT) switching in perpendicular magnetic tunnel junctions, the capability for scaling MRAM products increased markedly, enabling a 1-Gb device in 2019. Ongoing research will allow scaling to even higher capacities. Compared to traditional memories, STT-MRAM can save power, improve performance, and enhance system data integrity, which supports the growing computing demands for everything from data centers to Internet of Things (IoT) devices. This article provides a review of the technology that enabled present toggle and STT-MRAM products, future STT-MRAM products, and new MRAM technologies beyond STT.