Ulsan National Institute of Science and Technology (UNIST) announced that it has developed a magnetic tunnel junction (MTJ) device based on 'ruthenium oxide (RuO₂),' which is attracting attention as a next-generation material for realizing AI memory semiconductors capable of low-power and high-speed computation, and observed the reversal of tunnel magnetoresistance (TMR) for the first time in the world.

This study was jointly conducted by Professor Yoo Jeong-woo's team from the Department of Materials Science and Engineering at UNIST and Professor Son Chang-hee's team from the Department of Physics, and is expected to be an alternative that can overcome the limitations of switching speed and power consumption of existing ferromagnetic-based MRAM.

MRAM is a non-volatile memory that processes information using the 'spin' of electrons rather than electric charges, but due to its ferromagnetic nature, it is sensitive to external magnetic fields and has limitations in high-speed switching.

The research team synthesized ruthenium oxide (RuO₂) using an atomic-level thin-film deposition technique in a high vacuum and implemented a new MTJ device through lamination with an insulating layer and a ferromagnetic layer.

We experimentally demonstrated that the tunnel magnetoresistance value in the device substantially changes depending on the change in spin direction, which is an important achievement that shows the feasibility of memory devices utilizing ferromagnetic materials.

The results were published on June 20 in 'Physical Review Letters', the most prestigious journal in the field of physics.Researchers Noh Seung-hyun and Kim Gye-hyun participated in the study as first authors.

This study is part of the 'Limit Challenge R&D Project' that aims to provide rapid support for high-risk and high-impact topics starting in September 2024, and achieved results in less than a year from material synthesis to device measurement.

Kim Dong-ho, a director at the National Research Foundation of Korea, said, “This is the result of a combination of rapid support and researchers who boldly took on the challenge of the field of magnetic materials,” and added, “We will continue to provide support so that it can lead to the next leap forward in the semiconductor industry.”

This study is evaluated as an innovative technology for implementing low-power and high-speed characteristics of AI semiconductors, and plans are in place to implement more clear TMR inversion characteristics through follow-up research.