Physicists say they have conclusive proof of a third kind of magnetism

For roughly 90 years, textbooks sorted magnets into two families: ferromagnets, whose aligned spins create a net field, and antiferromagnets, whose alternating spins cancel out. A team led from SLAC National Accelerator Laboratory now says it has conclusive proof of a third family, called altermagnetism, in the crystal manganese telluride. The result appeared in Science.

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Lead author Daniel Jost, an associate scientist at SLAC and the Stanford Institute for Materials and Energy Sciences, said altermagnets combine the best of both older classes. The practical hope is memory and logic devices that are stable and fast.

Altermagnets, between ferromagnets and antiferromagnets

Altermagnets behave like antiferromagnets in one respect: neighboring spins point in opposite directions, so the net magnetization is zero and stray fields leave them undisturbed. They differ in the surrounding crystal. The environments around oppositely aligned spins are rotated relative to each other, which breaks a symmetry that conventional antiferromagnets keep. That change lets altermagnets carry spin-polarized currents, a property otherwise tied to ferromagnets and the one that makes information readable. The ScienceDaily version of the SLAC release sets out the contrast and notes that the term itself was only introduced in 2022.

Each older class has a weakness. Ferromagnets are easily knocked around by outside magnetic fields, which makes dense storage fragile, while antiferromagnets are stable but hard to read because they produce no net signal. Altermagnets, if they work as proposed, would be stable and readable at once, and Jost’s own phrase for the pairing is the best of both. Theorists had proposed the class on paper well before anyone had a clean experimental test, which is why the confirmation matters to the field.

A chirality test in manganese telluride

The team picked manganese telluride because it had been classed as an ordinary antiferromagnet for decades before theorists suspected it was altermagnetic. The test was chirality, a handedness in the material’s magnetic excitations. According to the SLAC news release, chiral materials scatter left-handed polarized X-rays differently than right-handed ones, so comparing the two reveals chirality, which conventional antiferromagnets lack. A difference between the two signals was the fingerprint the experiment looked for.

The measurements ran on the ID32 beamline at the European Synchrotron Radiation Facility in France. Rachel Nickel, a postdoctoral scientist there and a co-author, helped design and run the experiment. The first run was completed in 2024, and the team repeated it in early 2025 and reproduced the results. An earlier version of the work circulated as a preprint titled Chiral Altermagnon in MnTe, submitted on Jan. 29, 2025, which describes what its authors call the first direct experimental evidence of a chiral magnon in the material, measured with circular-dichroism resonant inelastic X-ray scattering.

Jost said the chiral signature gave the team solid experimental ground to say altermagnetism stands in a class of its own. SLAC’s release words the claim a little more carefully, as robust experimental confirmation that the third phase is real. Both phrasings come from Jost, and ScienceDaily’s version carries the stronger label of conclusive proof, a framing worth reading as the authors’ confidence rather than a closed debate.

Spintronics hopes and the next experiments

Nickel said altermagnetism was only proposed a few years ago and that the rapid progress in confirming these models is incredible. The paper, Chiral altermagnon in MnTe, appears in Science volume 394, issue 6823, page 541, with Matthias F. Kling listed among the coauthors. The research was supported in part by the Department of Energy’s Office of Science, and the release gives no dollar figure or grant number.

The applications SLAC names are spintronic memory, quantum technologies and more energy-efficient data centers. Those are aims rather than products: no device has been demonstrated, and a crystal measured at a synchrotron sits a long way from a chip. Spintronics tries to store and move information with electron spin instead of charge, and a material with zero net magnetization but readable spin currents would suit tightly packed memory cells that do not disturb their neighbors.

Proof here has a specific meaning. A single measurement technique, even one repeated a year later on the same instrument, shows that the signature is reproducible, and the chirality argument rules out ordinary antiferromagnetism in manganese telluride. It leaves open how many other crystals share the property and how strong the effect is at room temperature, questions the release does not address. Jost and Nickel frame the work as confirmation of a model first proposed on paper, with the engineering still ahead.

The stated next step is control. The researchers plan to examine how light and electricity influence altermagnetic states, since a memory element has to be switched as well as read. The release gives no timeline, and independent groups testing the same crystal with other probes will decide how firmly the label of a third magnetic family sticks.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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