Discovery of 2D Magnet with Four-Level Self-Control Capability

Domestic Joint Research Team Including IBS Research Fellow Kim Junsung Develops Potential Application for 'Spin Information Devices'

[Asia Economy Reporter Kim Bong-su] A new two-dimensional magnetic material with controllable magnetic states has been discovered.

The Korea Institute of Basic Science announced on the 17th that a domestic joint research team, including Research Fellow Kim Junsung of the Atomic Control Low-Dimensional Electron System Research Group, successfully synthesized a 2D magnet capable of controlling four different magnetic states. This breakthrough enables the induction of various spin alignment states within a single material, paving the way for diverse research on next-generation spin devices.

Two-dimensional magnets are one of the key materials required for implementing spin information devices, which are candidates for next-generation devices. However, 2D magnet candidate materials are rare, and magnetism typically appears only at very low temperatures, making it difficult to secure suitable materials. Last year, the research team succeeded in designing and synthesizing iron-germanium-telluride (Fe4GeTe2), a 2D layered material that maintains magnetism at high temperatures and conducts electricity.

Just as electronic devices consist of numerous transistors carrying binary information of 0s and 1s, spin information input and output require magnets with various magnetic states to be interconnected. Therefore, controlling magnetic states in 2D magnets has been an important challenge.

The research team focused on the fact that the magnetic state of Fe4GeTe2 is sensitively altered depending on the strength of interlayer magnetic coupling. To adjust the interlayer coupling strength, they planned experiments to substitute some iron atoms in Fe4GeTe2 with other atoms. Manganese, cobalt, gallium, and ruthenium atoms, which are similar to iron atoms, were selected as candidates. They calculated the magnetic states for each substitution and conducted actual synthesis and measurement experiments.

As a result, they discovered that iron-cobalt-germanium-telluride (Fe4-xCoxGeTe2), where iron is substituted with cobalt, can exhibit four different magnetic states. Fe4-xCoxGeTe2 shows different magnetic states depending on the cobalt atom concentration. These four magnetic states combine ferromagnetism and antiferromagnetism according to spin alignment, and perpendicular anisotropy and horizontal anisotropy according to direction.

The newly discovered material allows magnetic state control not only by cobalt concentration but also by adjusting the number of layers in the thin film. The four magnetic states appear within specific temperature ranges, which vary depending on the number of layers. Therefore, changing the number of layers results in different magnetic states even at the same temperature. This achievement represents the first synthesis of a 2D magnet whose magnetic state can be freely controlled, and it is expected that combining layers with different magnetic states will induce useful properties for spin information processing.

Research Fellow Kim Junsung stated, “We demonstrated through calculations and experiments that the magnetic state of 2D magnet candidate materials can be controlled by changing chemical composition and physical thickness,” adding, “This will be an important stepping stone for implementing multiple functions in spin devices using 2D magnets.”

This research was published online on the 14th in the international academic journal Nature Communications (IF 12.121).

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