Groundbreaking Discovery: Altermagnetism Found in Organic Crystal

In a groundbreaking study published in Physical Review Research on July 7, 2025, researchers from Tohoku University have identified altermagnetism in an organic crystal, marking a significant advancement in the field of magnetic materials.

This discovery introduces a new class of magnetic materials—altermagnets—that, despite lacking net magnetization, can influence the polarization of reflected light. The findings hold promise for the development of high-performance, flexible, and lightweight magnetic devices, potentially revolutionizing spintronics and related technologies.

Introduction to Altermagnetism

Altermagnetism represents a third category of magnetic order, distinct from traditional ferromagnetism and antiferromagnetism. In altermagnetic materials, there is no net magnetization; however, they exhibit spin-dependent electronic band structures due to broken time-reversal symmetry. This unique characteristic allows altermagnets to influence the polarization of reflected light, despite their lack of net magnetization. The concept of altermagnetism has been theoretically proposed and experimentally observed in inorganic materials, but its realization in organic compounds marks a significant advancement.

Details of the Discovery

The research team, led by Associate Professor Satoshi Iguchi from Tohoku University's Institute for Materials Research, focused on the organic crystal κ-(BEDT-TTF)₂Cu[N(CN)₂]Cl. Utilizing a newly derived general formula for light reflection based on Maxwell's equations, the team successfully measured the magneto-optical Kerr effect (MOKE) in the crystal. This precise optical measurement revealed three key features in the spectrum:

1. Edge peaks indicating spin band splitting.
2. A real component associated with crystal distortion and piezomagnetic effects.
3. An imaginary component linked to rotational currents.

These findings confirm the altermagnetic nature of the material and demonstrate the efficacy of the newly developed optical method.

Collaborative Effort

The study was a collaborative effort involving researchers from:

• Japan Synchrotron Radiation Research Institute.
• Kwansei Gakuin University.
• Tohoku University's Department of Physics.

This interdisciplinary collaboration underscores the complexity and significance of the research.

Implications and Future Prospects

The discovery of altermagnetism in an organic crystal opens new avenues for exploring magnetism in a broader class of materials, including organic compounds. Organic materials are known for their lightweight, flexible, and chemically tunable properties, making them ideal candidates for developing high-performance magnetic devices. Potential applications include:

• Flexible magnetic memory and logic circuits.
• Spin-based sensors.
• Quantum computing platforms exploiting the unique symmetry properties of altermagnets.

The tunable molecular structures of these compounds could enable engineers to custom-design magnetic properties for specific applications, leading to breakthroughs in wearable electronics, neuromorphic computing, and optically controlled spin devices.

Conclusion

This pioneering research by Tohoku University not only confirms the existence of altermagnetism in organic materials but also sets the stage for future developments in magnetic device technology. By leveraging the unique properties of organic altermagnets, scientists and engineers can explore new frontiers in spintronics and related fields, potentially leading to more efficient, flexible, and sustainable electronic devices.