A University of Central Florida-led team has delivered the first experimental evidence of altermagnetism in Co₁/₄TaSe₂, a layered transition-metal dichalcogenide with magnetic cobalt atoms intercalated between its weakly bound layers. The finding, published in Nature Communications by professor Madhab Neupane's group, gives semiconductor researchers a materials platform that combines the spin-current capabilities of ferromagnets with the stray-field immunity of antiferromagnets — a combination long sought for densely packed spintronic devices.

The commercial logic behind the work is straightforward. Conventional electronics move charge; spintronics proposes to move spin. As devices shrink, ferromagnets become a liability because their stray magnetic fields interfere with neighboring components. Antiferromagnets cancel those fields out but cannot generate or detect the spin currents that spintronic circuits need. Altermagnets — a magnetic class only recently theorized — promise both properties at once.

"These materials are distinguished from more conventional antiferromagnets by their ability to generate and detect spin currents without the negative effect of producing stray fields," Neupane says. "This new property makes them very well positioned for use in many different applications — including spintronics, ultrafast memory devices, terahertz networks and energy-efficient electronics."

How the team proved it

The researchers used angle-resolved photoemission spectroscopy (ARPES) to map the electronic structure of Co₁/₄TaSe₂ and confirm the predicted magnetic state. Their approach ran in two stages. First, high-resolution, spin-insensitive ARPES measured a characteristic splitting in the material's electronic energy bands — a necessary but not sufficient signature of altermagnetism, since ferromagnets can produce similar band splitting. Then spin-resolved ARPES confirmed that the split states carried opposite spin polarizations, the decisive evidence that the effect is altermagnetic rather than ferromagnetic.

"Our approach was to use higher-resolution methods that were insensitive to the electron's spin to measure the splitting in the energy levels," Neupane explains. "Then, we complemented this measurement with spin-resolved ARPES to conclusively tell if this looks like altermagnetism."

Surface quality posed the main experimental hurdle. Photoemission is acutely sensitive to a material's surface, so collaborators grew high-quality Co₁/₄TaSe₂ samples that Neupane's team then screened for ultraclean surfaces before mapping electronic behavior. The measurements consistently matched theoretical predictions.

"The significance became clear once the experimental measurements consistently matched our theoretical predictions," Neupane says. "Seeing those independent pieces of evidence converge gave us confidence that we had identified a genuine layered altermagnet."

Why the layered structure matters

Altermagnetism alone would make the material notable. Its position in the transition-metal dichalcogenide family makes it considerably more useful. TMDs consist of atomically thin, weakly bound layers that researchers can separate and restack into thin-film structures — the same property that has put layered materials on the roadmap for ultrasmall transistors and optical devices.

In Co₁/₄TaSe₂, the intercalated cobalt atoms between layers help produce the unusual magnetic order. The structure is also highly tunable: researchers can modify the material and observe how the changes affect its electronic and magnetic behavior, something bulk altermagnet candidates do not readily allow.

The team also resolved a question that predated the study: whether altermagnetic signatures in layered materials originate at the surface or in the bulk. Their measurements show the relevant electronic state comes primarily from within the material itself and carries clear signatures of altermagnetic order.

"Evidence for altermagnetism in a versatile materials platform opens a lot of new possibilities," says Milo Sprague, the study's lead graduate student researcher. "There's currently a lot of debate in altermagnetic theory about how the spin-polarized electronic states interact with other magnetic phenomena. Now we have a material that we can easily modify to explore these new questions."

What remains unresolved

The physics is not settled. Scientists do not yet fully understand why the altermagnetic state forms in this material, why it wins out over competing magnetic structures such as ferromagnetism and other forms of antiferromagnetism, or how it behaves under device-relevant conditions. Theoretical work suggests that competition among electron interactions may determine which magnetic state emerges, but researchers have not established how completely those theories describe real materials.

"There are many details to the theory of how altermagnets work that haven't been explored or verified yet," Neupane says. "Now that we have identified several platforms for answering these questions, more advanced studies into these materials are underway."

For the device community, the near-term value is a working experimental platform rather than a product. Layered materials are already under investigation for extremely small transistors and optical technologies, and spin currents are being explored as a new channel for transmitting digital information. A material that merges the two — thin, adaptable, capable of controlling electron spin without stray-field interference — sits at the intersection of both research tracks.

"As electronic devices continue to shrink, researchers need new materials that can operate faster while consuming less energy," Neupane says. "If this approach proves viable, then layered altermagnets will be at the forefront of electronics development."

The study, "Observation of Altermagnetic Spin-Splitting in an Intercalated Transition Metal Dichalcogenide," appears in Nature Communications (DOI: 10.1038/s41467-026-76784-x). With tunable Co₁/₄TaSe₂ now in hand, follow-up studies into how altermagnetic order interacts with other magnetic and electronic phenomena are already underway.