DATE2025.06.17 #Press Releases

Room-Temperature Control of Exchange Bias Achieved Using Weyl Antiferromagnets

— Pioneering New Spintronic Technologies Through Functional Design Harnessing Exotic Magnetic Order —

Summary

A research group led by graduate student Mihiro Asakura, Project Associate Professor Tomoya Higo (at the time of research), and Professor Satoru Nakatsuji of the Graduate School of Science at the University of Tokyo has demonstrated that at the interface between the Weyl antiferromagnet Mn₃Sn and a ferromagnet, exchange bias effects—arising from magnetic coupling—can be induced and controlled at room temperature using external magnetic fields. Exchange bias effects are widely used in magnetic random-access memory (MRAM), a type of non-volatile memory with advantages such as low power consumption and high durability. In MRAM, the magnetic properties of the ferromagnetic recording layer are stabilized and controlled via magnetic coupling with another magnetic layer, typically an antiferromagnetic one. However, it has traditionally been considered difficult to establish and control this effect at room temperature without varying the temperature. In this study, the researchers employed the Weyl antiferromagnet Mn₃Sn, which exhibits a characteristic chiral antiferromagnetic order, as the antiferromagnetic layer and evaluated its magnetic coupling with a ferromagnetic layer. They confirmed that magnetic coupling forms between the chiral antiferromagnetic order of Mn₃Sn and the ferromagnetic order (magnetization) of the ferromagnetic layer. Furthermore, they demonstrated that the resulting exchange bias effect can be controlled not only by the conventional field-cooling process, but also by (i) simply applying a magnetic field at room temperature (an isothermal process), and (ii) changing the type of ferromagnetic material used in the junction. These findings present a new design principle for flexibly controlling the magnetization of ferromagnets by switching the magnetic state of antiferromagnets with exotic magnetic orders. This approach may lead to simplified fabrication processes for magnetic memory devices. The results are also expected to contribute to the advancement of high-performance spintronic devices that exploit novel magnetic coupling between ferromagnetic and antiferromagnetic materials. In particular, within the context of the JST Mirai Program, which promotes the development of fusion devices combining spintronics and optoelectronic technologies, this study adds new electronic functionality to the core material Mn₃Sn. The ability to control magnetic information through magnetic coupling represents a significant step toward the design and implementation of next-generation information devices.

Figure: Control of exchange bias in Mn₃Sn/ferromagnetic bilayer films by applying magnetic field isothermally

Related Links

The Institute for Solid State Physics, The University of Tokyo,
Japan Science and Technology Agency（JST）

Journals

Journal name	Nano Letters
Title of paper	Magnetic Field Switching of Exchange Bias in a Metallic FM/AFM Heterostructure at Room Temperature