Frontier Research Institute for Interdisciplinary Sciences
Tohoku University

Spintronics-based very large scale integrated circuits (VLSIs) are attracting great attention these years since they consume no energy to retain bit information. Since the information is stored as the magnetization of ferromagnetic materials, the electrical manipulation of magnetization direction without resorting to an external magnetic field is now being developed as a fundamental spintronics technology. In recent years, increasing attention has been paid to a new electrical magnetization switching scheme based on spin-orbit torque (SOT), which allow high speed write operation and relaxed design parameters for spintronics memory. SOT is a torque brought about by in-plane current flowing in a heavy metal (Ta, W, Pt etc.) channel under the ferromagnetic thin layer via the spin-orbit interaction, which acting on the magnetization in ferromagnetic layer and thus switch the magnetization in it. Until now, there still some issues unsolved for the development of the magnetic random access memory (MRAM) based on SOT-MTJ (magnetic tunnel junction) devices. For example, there is no consensus about the detail physics behind the SOT and SOT-induced magnetization switching mainly due to a lack of effective experimental methologies, and material systems or device structures allowing magnetization switching with lower current is also required. In our studies, we focus on the investigation of the origin of SOT and the new material systems for SOT switching, the development of SOT-MTJ devices with new structures, and the construction of MRAM technology for realizing high performance and low power consumption.