SLAC Confirms Altermagnetism as Third Class of Magnetism in MnTe Study

For nearly 90 years, physicists sorted every magnetic material into two categories. A team led by the Department of Energy's SLAC National Accelerator Laboratory has now confirmed a third: altermagnetism, demonstrated experimentally in manganese telluride and published in Science (DOI: 10.1126/science.adv3196).

The result matters for electronics because altermagnets combine two properties that engineers previously had to choose between. They carry no net magnetization, like antiferromagnets, so stray magnetic fields cannot scramble stored data. At the same time, they can generate spin-polarized currents, like ferromagnets, which makes the stored information readable.

What did the researchers actually find?

Lead author Daniel Jost, associate scientist at SLAC and the Stanford Institute for Materials and Energy Sciences, put the finding in context. "In the past few years, scientists have observed phenomena that don't fit neatly into the ferromagnetism-antiferromagnetism dichotomy," he said. "We believe our results provide robust experimental confirmation that this third phase -- altermagnetism -- is real."

The team tested manganese telluride (MnTe), a compound long classified as an ordinary antiferromagnet. The decisive evidence was chirality, a handedness in the material's magnetic structure. An object is chiral when its mirror image cannot be matched to the original, the way a left hand cannot fit a right-handed glove. Conventional antiferromagnets do not show this characteristic chiral signature.

The structural cause is subtle. Altermagnets carry alternating spin orientations, up-down-up-down, but the crystal structures around the oppositely aligned spins are rotated relative to one another. That rotation breaks a symmetry present in ordinary antiferromagnets and lets altermagnets support spin currents despite zero net magnetization. The term "altermagnets" was introduced in 2022.

How did the X-ray experiment work?

The measurements took place at the European Synchrotron Radiation Facility (ESRF) in France, on the ID32 beamline, which produces precisely controlled polarized X-rays. The researchers used circularly polarized light, whose electric fields rotate in either a left-handed or right-handed direction. A chiral material scatters these two beams differently; a non-chiral one scatters them identically.

Manganese telluride scattered the two polarizations differently, exactly the signal expected from altermagnetism and absent in a conventional antiferromagnet. "This chiral signature gave us the solid experimental ground to say altermagnetism stands in a class of its own," Jost said.

The team first ran the experiment in 2024 and returned in early 2025 to repeat it. The reproduction strengthened the evidence for the new phase. Co-author Rachel Nickel, a postdoctoral scientist at ESRF who helped design and conduct the beamline work, noted the pace of the field. "Altermagnetism was only proposed a few years ago, and the rapid progress in confirming these models is incredible," she said.

Why does the third class matter for devices?

The finding has direct relevance for spintronics, the field that uses electron spin rather than only electrical charge to store and process information. Spintronic devices could run faster, resist interference and consume substantially less electricity, which is valuable for memory, large data centers and other heavy information-processing workloads.

The two known magnet classes each block that goal in a different way. Jost explained the trade-off plainly. "Ferromagnets are too easily influenced by magnetic fields," he said. "Antiferromagnets fix that problem, but they are practically invisible -- so you can't easily read the data stored in them or use them to drive efficient spin currents."

Altermagnets offer a way out. "Altermagnets combine the best of both," Jost said. "They have zero net magnetization, so they're stable, but they still have the capability to generate spin-polarized currents needed to easily extract information. That gives you an additional degree of freedom to work with."

What comes next?

The study, partially funded by the DOE Office of Science, establishes altermagnetism as a confirmed magnetic phase rather than a proposed one. The next step, according to the researchers, is learning to control altermagnetic states with external influences such as light and electricity. Mastering that control is the prerequisite for practical devices in quantum technologies, computer memory and more efficient data centers.

In short, the field now has a new class of stable, readable magnetic materials to engineer, and MnTe is the first confirmed member of it.