Real-time observation shows new hybrid writing method is fast and reliable in spin-based memory

Spin-based memory devices represent an emerging technology that may one day replace conventional, charge-based devices. A promising spin-based memory called spin-transfer torque (STT) magnetic random access memory can be used as a write method to switch magnetization to the desired state, but struggles with operating speed and reliability.

An alternative write method, voltage controlled magnetic anisotropy (VCMA), reduces the write current for faster magnetization switching but also increases the error rate. Spin-orbit torque (SOT), another alternative, reduces error by separating the read and write current paths, but enlarges the required size of memory cells.

To simultaneously address the issues of speed and reliability, Inokuchi et al. combined VCMA and SOT to create a new write method. They tested their design in a novel spin-based memory type called voltage-control spintronics memory (VoCSM) and found the new design can speed up magnetization switching without increasing the error rate. The hybrid method also has a high write durability of over 10¹³ write cycles using short write pulses of two nanoseconds, making it a promising spin-based memory with the potential to shape the next generation of MRAM.

The authors examined the reason behind its faster speed by measuring real-time magnetization switching in the new device. By applying a pulse to the write line and measuring sub-nanosecond-order dynamics, the authors determined that the VCMA effect lowers the switching energy barrier between spin states, therefore reducing write current and accelerating magnetization switching. Tomoaki Inokuchi, one of the authors, said that this real-time observation method will help further improve the device in future work.

Source: “Real-time observation of fast and highly reliable magnetization switching in Voltage-Control Spintronics Memory (VoCSM),” by T. Inokuchi, H. Yoda, K. Koi, N. Shimomura, Y. Ohsawa, T. Kato, S. Shirotori, M. Shimizu, H. Sugiyama, S. Oikawa, B. Altansargai, and A. Kurobe, Applied Physics Letters (2019). The article can be accessed at https://doi.org/10.1063/1.5097063 .