In collaboration with Tohoku University, the National Institute for Materials Science, Osaka University and the Japan Synchrotron Radiation Research Institute, the researcher has developed a novel very thin iron-iridium (FeIr) magnetic material for voltage-controlled magnetic memory that achieves highly efficient spin control by voltage that is about three times as efficient as conventional spin control.

Properties of the developed Ir-doped ultra-thin Fe film (red star) and a schematic of the device structure

Magnetic random access memory (MRAM) is expected as a promising working memory with low stand-by power using non-volatility of magnetism. However, since an electric current is used to write information, energy for writing process is high due to heat generation by the current. Consequently, the drive power is a few orders of magnitude greater for MRAM than for current semiconductor-based memories, which are operated by electric-field. This limits the range of applications of MRAM. On the other hand, information can be written using a voltage pulse in voltage-torque MRAM. It is expected that ideal small non-volatile memory with low drive power will be developed. To put voltage-torque MRAM into practical application, the challenge is to increase the efficiency of spin control by voltage.

In previous works, conventional iron-cobalt (FeCo)-based alloys were used. The researcher discovered that the efficiency of spin control by voltage can be increased about three-fold by using an Ir-doped ultra-thin Fe film. In addition to the efficiency of voltage control, perpendicular magnetic anisotropy, which is important to show the scalability of voltage-torque MRAM, is also improved simultaneously. For the first time, he has achieved the target performance for practical voltage-torque MRAM, such as last-level cache memory.

The researcher will develop a mass-production technology for the developed material. He will also develop new materials and structures to further enhance perpendicular magnetic anisotropy and the efficiency of spin control by voltage.