磁気トンネル接合素子におけるスピントルク磁化反転とその応用

摘要

Spin-transfer-torque (STT) induced magnetization switching was investigated in MgO-based magnetic tunnel junctions (MTJs). The concept of STT switching was first introduced theoretically, followed by an experimental demonstration in a metallic giant magnetoresistance (MR) element and A10-based MTJ. However, the MR elements in the early stage resulted in rather poor MR effects, indicating that they have poor prospects in applications for hign-density magnetoresistive random access memories (MRAMs). Amid such unfavorable circumstances, we were able to demonstrate STT switching in low-resistive and high-magnetoresistive MgO-MTJs, which eventually triggered the development of high-density MRAMs. Notable advances have been made toward the commercialization of high-density STT-MRAMs by combining new materials. Furthermore, new spintronics devices such as high-frequency driven devices are being developed by utilizing STT-induced magnetization dynamics. Their great performance potential means that expectations for new spintronics devices are better than ever before.