MENLO PARK, California — Physicists have delivered what they describe as conclusive experimental proof of a third kind of magnetism, ending a debate that has shaped the field for nearly a century. The finding, reported on 30 October 2026 by a team led by the U.S. Department of Energy's SLAC National Accelerator Laboratory, confirms that a material called manganese telluride behaves as an "altermagnet" — a class of magnet that combines traits long thought to belong to two mutually exclusive families.
The result, published in the journal Science, supplies the missing piece of evidence researchers had sought since the concept was proposed in 2022: a distinct "handedness," or chirality, in the material's magnetic structure that conventional antiferromagnets should not show. According to the team, that signature settles the question of whether altermagnetism deserves to stand as a category of its own — and opens a path toward faster, more energy-efficient electronics built on electron spin.
"Researchers have been compiling evidence of a third type of magnetism that bridges the qualities of these two classes," said lead author Daniel Jost, an associate scientist at SLAC and the Stanford Institute for Materials and Energy Sciences. "We believe our results provide robust experimental confirmation that this third phase — altermagnetism — is real."
Illustration: Three mirrors showing ferromagnetism, antiferromagnetism and the twisted spin pattern of altermagnetism.
What Happened
Jost's team set out to test a specific prediction. If manganese telluride (MnTe) is truly an altermagnet, its internal magnetic structure should be chiral — asymmetric in the way a left hand differs from a right hand, so that it cannot be superimposed on its mirror image. A conventional antiferromagnet, with its neatly cancelling alternating spins, should show no such handedness.
To look for that signature, the researchers took MnTe to the European Synchrotron Radiation Facility (ESRF) in France, using a beamline known as ID32 that can produce highly controlled, circularly polarized X-ray beams. The principle of the test is straightforward: chiral materials scatter left-handed polarized X-rays differently from right-handed ones, while non-chiral materials scatter both beams the same way.
The MnTe sample scattered the two beams differently — a clear chiral signal that, according to the team, should not exist 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 initial experiment was completed in 2024, and the team repeated it in early 2025, confirming the earlier result before publishing.
Rachel Nickel, a postdoctoral fellow at ESRF who helped design and conduct the experiment, said the speed of the field's progress had been striking. "Altermagnetism was only proposed a few years ago, and the rapid progress in confirming these models is incredible," she said.
Illustration: Researchers at a synchrotron beamline directing polarized X-rays at a crystal sample to test for chirality.
Background
For most of modern physics, magnetism came in just two varieties. In ferromagnets — the familiar magnets that hold notes to a refrigerator door and swing a compass needle north — all of the electrons' spins point in the same direction, producing an observable magnetic field. Humans have used such magnets since ancient times.
The second category arrived in 1933, when scientists identified antiferromagnets: materials whose electron spins alternate up-down-up-down, cancelling each other out so that no net magnetic effect appears. For nearly 90 years, that two-category system dominated physicists' understanding of magnetism.
Then, in recent years, some materials began to misbehave. They showed the alternating spin pattern and zero net magnetization of an antiferromagnet, yet they could also carry spin-polarized currents — a ferromagnetic-like ability that was supposed to be impossible for such materials. In 2022, researchers proposed the term "altermagnets" for this puzzling class.
The proposed explanation involved geometry. In an altermagnet, the crystal lattice surrounding the "up" spins is rotated relative to the lattice surrounding the "down" spins. That geometric twist breaks a symmetry and, theorists argued, should give the material a distinct handedness — chirality — in its electronic and magnetic structure. By 2024, several lines of evidence pointed in that direction, but the direct experimental test of chirality was still missing. The new study claims to supply it.
Manganese telluride was a fitting test case: it had been considered an ordinary antiferromagnet for decades, until a few years ago when researchers began to suspect it was altermagnetic. Confirming that suspicion in such a well-studied material makes the result harder to dismiss as an oddity of an exotic compound.
Why It Matters
The stakes go beyond taxonomy. Altermagnets are prized candidates for spintronics, a branch of electronics that uses both an electron's charge and its spin to store and move information, rather than charge alone. Spintronic devices have the potential to be faster, more robust and far less power-hungry than conventional electronics — an attractive prospect for data centers whose energy consumption keeps climbing.
Each older magnetic class has a flaw that has limited spintronic devices. Ferromagnets are easily disturbed by external magnetic fields: as Jost put it, a permanent magnet in a pocket could flip the bits of a ferromagnetic device and scramble its stored information. Antiferromagnets solve the stability problem but create a new one — they are practically invisible to readout, so extracting data from them or driving efficient spin currents through them is difficult.
"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."
If that combination can be engineered reliably, it could underpin a new generation of memory devices, quantum technologies and data-center hardware that stores more information, switches faster and wastes less energy as heat. The researchers stress that this is a materials-science foundation, not a finished product: turning a confirmed magnetic phase into commercial devices will take years of further work.
Illustration: Futuristic low-power computer chips with electron spin currents flowing through circuits.
What Happens Next
The team's next steps, as described in the SLAC report, focus on control: exploring how altermagnetic states can be influenced and manipulated using light and electricity, with the aim of making them useful in practical spintronic devices. Other groups are expected to test whether the chiral signature appears in additional candidate materials, and whether it survives at the temperatures and scales that real devices require.
The result is also likely to sharpen a broader debate in condensed-matter physics about how many magnetic phases nature actually allows. A confirmed third class, established only four years after it was named, suggests the field's classification of magnetic order may still be incomplete — and that other overlooked materials could be hiding similar surprises.
For now, the claim rests on the published Science paper and its two rounds of synchrotron measurements. Independent replication in other laboratories, using other techniques, will be the usual next test for a result of this kind. But if the chiral signature holds up, textbooks will need a new chapter: after nearly a century of two magnetisms, there are three.
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FAQ
What is altermagnetism?
Altermagnetism is a proposed third class of magnetism, alongside ferromagnetism and antiferromagnetism. Altermagnets have alternating electron spins and zero net magnetization like antiferromagnets, but — according to the new research — they also carry spin-polarized currents like ferromagnets, thanks to a geometric twist in their crystal lattice.
How did researchers prove altermagnetism is real?
The SLAC-led team tested manganese telluride at the European Synchrotron Radiation Facility in France, scattering circularly polarized X-rays off the material. Chiral materials scatter left- and right-handed beams differently; the team found that distinct chiral signal, which a conventional antiferromagnet should not produce. They repeated the experiment in early 2025 and obtained the same result.
Why was chirality the missing piece?
Earlier evidence for altermagnetism was suggestive but indirect. Chirality — a handedness in the material's structure, like the difference between a left and a right hand — provides a clean test: it distinguishes an altermagnet from an ordinary antiferromagnet even though both have alternating spins.
What is manganese telluride?
Manganese telluride (MnTe) is a compound long classified as an antiferromagnet. In recent years researchers suspected it was actually altermagnetic, making it an ideal test case: confirming altermagnetism in such a familiar material strengthens the case that the phase is a genuine, general phenomenon rather than a quirk of one exotic sample.
When could altermagnets appear in real devices?
Not soon. The new result is a fundamental physics confirmation, not a product announcement. Researchers must first learn to control altermagnetic states with light and electricity, and to make them work at practical temperatures and scales, before spintronic memory or computing devices based on them can reach the market.
Sources
SLAC National Accelerator Laboratory, via Phys.org, "Confirming altermagnetism: A geometric twist offers experimental proof," 30 October 2026; Daniel Jost et al., "Chiral altermagnon in MnTe," Science (2026), DOI: 10.1126/science.adv3196; European Synchrotron Radiation Facility ID32 beamline, as reported by SLAC/Phys.org, 30 October 2026.
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