Progress and Application Perspectives of Voltage-Controlled Magnetic Tunnel Junctions

This article discusses the current state of development, open research opportunities, and application perspectives of electric-field-controlled magnetic tunnel junctions that use the voltage-controlled magnetic anisotropy effect to control their magnetization. The integration of embedded magnetic random-access memory (MRAM) into mainstream semiconductor foundry manufacturing opens new possibilities for the development of energy-efficient, high-performance, and intelligent computing systems. The current generation of MRAM, which uses the current-controlled spin-transfer torque (STT) effect to write information, has gained traction due to its nonvolatile data retention and lower integration cost compared to embedded Flash. However, scaling MRAM to high bit densities will likely require a transition from current-controlled to voltage-controlled operation. In this perspective, an overview of voltage-controlled magnetic anisotropy (VCMA) as a promising beyond-STT write mechanism for MRAM devices is provided and recent advancements in developing VCMA-MRAM devices with perpendicular magnetization are highlighted. Starting from the fundamental mechanisms, the key remaining challenges of VCMA-MRAM, such as increasing the VCMA coefficient, controlling the write error rate, and achieving field-free VCMA switching are discussed. Then potential solutions are discussed and open research questions are highlighted. Lastly, prospective applications of voltage-controlled magnetic tunnel junctions (VC-MTJs) in security applications, extending beyond their traditional role as memory devices are explored.