Scientists at Tohoku University in Japan have confirmed the existence of a new type of magnet called an altermagnet that can bend light despite having no usual magnetic attraction. Their discovery, published in the journal Physical Review Research, introduces a third class of magnetic materials beyond traditional ferromagnets and antiferromagnets. This breakthrough was achieved by studying an organic crystal named κ-(BEDT-TTF)₂Cu[N(CN)₂]Cl, a promising candidate for altermagnetism.
Associate Professor Satoshi Iguchi led the team at Tohoku University’s Institute for Materials Research. He explained that unlike typical magnets, altermagnets do not show net magnetization, but they influence how light reflects by changing its polarization. This makes altermagnets difficult to study with common optical methods. To reveal the magnetic behaviors, the team developed a new optical formula based on Maxwell’s equations.
Using this formula, they measured the magneto-optical Kerr effect (MOKE) on the crystal. MOKE occurs when light changes polarization after reflecting off a magnetic surface. Their measurements exposed unique magnetic and electronic properties that are invisible with standard techniques. The presence of altermagnetism in this organic material was proven through detailed analysis of the light reflection and optical conductivity.
The discovery extends known magnetic behavior to organic compounds, which tend to be lightweight and flexible. These features could allow for the creation of new magnetic devices, including faster computer memories or components in quantum computing. Iguchi said this opens up chances to explore magnetism in broader materials and develop advanced magnetic technologies.
This research builds on predictions made about altermagnets since 2019. Since then, scientists have found over 200 materials exhibiting similar properties. The field gained recognition in 2024 when Science magazine named altermagnetism the top physics breakthrough. The Tohoku University team’s new optical technique could help uncover more about these materials and their applications.
The international collaboration involved experts from the Japan Synchrotron Radiation Research Institute and physics departments at Kwansei Gakuin University and Tohoku University. Together, they have set the stage for future investigations in magnetic materials for electronics and other technologies.
This confirmation of altermagnetism in an organic crystal marks a key step forward in understanding magnetism’s diverse behaviors. It may inspire innovations in lightweight, flexible devices with magnetic functions that go beyond what traditional magnets can offer.
