A Third Kind of Magnetism
by: Marcus Webb

A Third Kind of Magnetism: What UCF Found and Where It Leads

Below about minus 139 degrees Fahrenheit, the cobalt atoms wedged between the layers of a crystal called Co1/4TaSe2 settle into a pattern that cancels their magnetism out. In each sheet the atoms’ spins point one way, and in the next sheet they point the other way, so the crystal as a whole produces no magnetic field. Yet the electrons moving through it still sort themselves by spin, the way they do inside an ordinary magnet.

That combination is the signature of altermagnetism. A team led by University of Central Florida physicist Madhab Neupane reports finding it in this layered compound in the journal Nature Communications. Since UCF publicized the work in mid-September, it has traveled across science sites and news feeds, some of them under headlines saying researchers had discovered a new magnetic state.

They hadn’t.

Theorists proposed altermagnetism about seven years ago, and experiments confirmed it in 2024. What the UCF group added is a new material that shows it, and the material is the useful part: thin, stackable sheets of the kind engineers already know how to peel apart and build into devices. The paper itself has been online since Aug. 20.

Two kinds of magnet, then a third

For most of history, magnetism came in one flavor. In a ferromagnet, the iron in a fridge magnet for example, the tiny magnetic moments of the atoms line up in the same direction and add together into a field you can feel. That field is what makes ferromagnets useful in hard drives and memory chips. It is also a problem when components get small, because each magnetic bit leaks a stray field that can disturb its neighbors.

About a century ago physicists identified a second kind, the antiferromagnet, where neighboring moments point in opposite directions like the squares of a chessboard. The moments cancel, so there’s no stray field. The cost is that antiferromagnets are hard to read. With no net magnetism, an antiferromagnetic bit gives off almost no signal that electronics can detect.

An altermagnet looks like an antiferromagnet on the surface. Neighboring moments still alternate and still cancel. The difference is in the crystal around them. In an altermagnet, the arrangement of atoms surrounding a spin-up site is rotated relative to the arrangement around a spin-down site. That rotation means electrons with opposite spins end up with different energies depending on the direction they travel through the crystal. Physicists call it spin splitting. In practice it gives a material with no outside field some of the electrical behavior of a ferromagnet.

Tomas Jungwirth of the Institute of Physics of the Czech Academy of Sciences, one of the theorists behind the idea, said in his institute’s 2024 announcement that altermagnets “can combine merits of ferromagnets and antiferromagnets, which were thought to be fundamentally incompatible.”

Seven years from theory to a growing list of materials

The idea came out of Prague and Mainz.

Groups there published a series of theory papers starting around 2019, coined the name “altermagnet” in 2021 and laid out the framework in Physical Review X in 2022. The first direct experimental proof followed in early 2024. Since then the list of confirmed materials has been growing.

Date Milestone Material Published in
2019–2021 Prague and Mainz theorists predict a third magnetic class and name it Theory Series of papers
Dec. 2022 Framework and research agenda for the field Theory Physical Review X
Feb. 14, 2024 First direct measurement of altermagnetic spin splitting Manganese telluride (MnTe) Nature
Dec. 11, 2024 Altermagnetic order imaged and controlled in microscopic devices MnTe Nature
March 18, 2025 Metallic altermagnet that holds its order at room temperature KV2Se2O Nature Physics
Aug. 20, 2026 Spin splitting in a layered, intercalated crystal Co1/4TaSe2 Nature Communications

The 2024 manganese telluride paper, led by the Prague group with partners in Switzerland, Germany, Austria and Britain, used light from a synchrotron to map the energies of the material’s electrons. The spin splitting matched what the theory had predicted. Manganese telluride had been treated as a textbook antiferromagnet for decades, and the Czech institute noted that more than 200 materials have now been flagged as altermagnet candidates, many of them long studied without anyone noticing.

What the UCF team measured

Neupane’s group used the same basic technique, angle-resolved photoemission spectroscopy. It fires light at a crystal, knocks electrons out of it and records their energy and direction, which lets researchers reconstruct how electrons behave inside. The measurements were made at two Department of Energy synchrotrons, the Stanford Synchrotron Radiation Lightsource at SLAC and the Advanced Light Source at Lawrence Berkeley National Laboratory.

The team first spotted electronic bands splitting in two. A second, spin-sensitive pass showed that the two halves carried opposite spins and that the dominant spin flipped as they moved around the crystal’s electronic map, in the alternating pattern the theory predicts. When they warmed a sample to 200 kelvin, above the point where its magnetic order breaks down, the split features faded. Cooling it again brought them back.

Neupane said in UCF’s release that once the measurements kept matching their calculations, the team was confident “that we had identified a genuine layered altermagnet.” The paper’s authors include researchers at the University of Notre Dame, George Mason University and Hiroshima University in Japan. Among them is George Mason theorist Igor Mazin, who has published earlier theory work on altermagnetism, including on manganese telluride. The same group had already reported similar signatures in a sister compound, built on niobium instead of tantalum, in a 2025 preprint the paper cites.

UCF’s release lists one funder, a Department of Energy Office of Science award. The paper’s own funding statement names a second, the Army Research Office. Its cooperative agreement supported three of the authors at Notre Dame and George Mason. Japan’s science agency funded the Hiroshima work.

Why stackable sheets matter

Co1/4TaSe2 belongs to a family called transition-metal dichalcogenides. These are crystals made of atom-thin sheets held together only weakly, so they can be split into very thin flakes and stacked with other materials. In this one, cobalt atoms slipped between the sheets supply the magnetism, and changing what sits between the layers changes how the material behaves.

That tunability is why the UCF result drew attention. The paper calls the compound unique among the altermagnets it discusses because of its layered structure, and the authors name the next step: stacking it with superconductors and other exotic materials in thin layered devices. UCF also reports that the team traced the signal to the bulk of the crystal, not just its surface, which had been an open question for layered candidates.

Where the technology could lead

The field’s main target is spintronics, electronics that carry information in an electron’s spin as well as its charge. Spin already does real work in computers. Commercial magnetic memory reads and writes its bits with spin-polarized currents from ferromagnets, and the stray fields of those ferromagnets limit how tightly the bits can be packed. The 2024 Nature paper on manganese telluride points out that altermagnets could produce the same kind of currents without the net magnetization that caps a memory’s capacity and speed.

The speed argument comes from antiferromagnets, whose experimental bits have already shown they can be made smaller, faster and more energy-efficient than ferromagnetic ones. The Nottingham team’s Nature paper lists ultrafast dynamics among the traits altermagnets share with them. The University of Nottingham team that imaged the order in 2024 said in its announcement that altermagnets could make microelectronic components and memory up to a thousand times faster. That figure is the researchers’ projection. No altermagnetic memory has been built to test it. Neupane’s list of possible uses in UCF’s release covers similar ground: spintronics, ultrafast memory, terahertz networks and lower-power electronics.

A second line of work is about steering spin, not just storing it. In a theory paper in Science Advances, announced by LSU in September, Louisiana State University physicist Constantin Schrade and Mathias Scheurer of the University of Stuttgart calculated that the boundaries between magnetic regions inside an altermagnet could bend and focus electrons like a lens, sending spin-up and spin-down electrons along different paths. “Then we can determine where spin-up goes and where spin-down goes,” Schrade said in LSU’s announcement. He told LSU’s student newspaper, The Reveille, that the long-term payoff would be cheaper logic operations, and pointed to energy-hungry AI data centers as one place that would matter.

What stands between the lab and a device

Temperature, first. Co1/4TaSe2 holds its altermagnetic order only below 178 kelvin, about minus 139 degrees Fahrenheit, and the key measurements were made at 7 kelvin, a few degrees above absolute zero. Chips have to work at room temperature. Manganese telluride orders up to about 310 kelvin, roughly body temperature, and the 2025 Nature Physics material holds its order at room temperature. So the UCF crystal is better read as a test bed for physics questions than as a component candidate, which is how its own authors describe it.

Those physics questions remain open. The UCF release says scientists still don’t fully understand why altermagnetic order forms in some materials and not others, or how it interacts with other magnetic effects. Neupane called practical use conditional in the same release. Layered altermagnets would be at the forefront of electronics development, he said, “if this approach proves viable.” Schrade told The Reveille that any firm application of his work is still a stretch, given how much basic science remains.

The studies the paper cites point to what comes next: thin films of altermagnets, few-layer stacks whose spins can be controlled electrically, and layered structures that let a current manipulate spin transport. The UCF team says further studies on its materials are already underway.

Sources

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