A team led by physicists at the SLAC National Accelerator Laboratory says it has gathered the clearest experimental evidence yet for altermagnetism, a proposed third class of magnetism that had existed mainly as theory since researchers first described it in 2022.
Ordinary magnets fall into two camps: ferromagnets, in which atomic spins line up in the same direction to produce a net magnetic field (the kind that sticks to a refrigerator), and antiferromagnets, in which neighboring spins point in opposite directions and cancel out, leaving no external field. Altermagnets are proposed to behave like antiferromagnets from the outside — no stray field — while still generating the spin-sorted electrical currents associated with ferromagnets, a combination theorists had called impossible under the old classification.
Chirality in manganese telluride
To test the idea, the team studied manganese telluride, a compound long filed away as an ordinary antiferromagnet, at the European Synchrotron Radiation Facility in Grenoble, France. Firing circularly polarized X-rays at the material, researchers compared how it scattered left-handed versus right-handed light — a test for "chirality," a directional asymmetry conventional antiferromagnets should not show. The two beams scattered differently, the signature altermagnetism predicts. The team first ran the experiment in 2024, reproduced it in early 2025, and published the results this week in the journal Science.
"This is robust experimental confirmation that altermagnetism is real," said Daniel Jost, the study's lead author and an associate scientist at SLAC and the Stanford Institute for Materials and Energy Sciences. Altermagnets, he said, "combine the best of both" conventional magnetic types.
"There's been rapid progress in confirming these models over the past couple of years."
Rachel Nickel, postdoctoral scientist at the European Synchrotron Radiation Facility
Because altermagnets carry no net external field, they are largely immune to the stray magnetic interference that can corrupt data in conventional magnetic memory, while their internal spin currents could make stored information faster to read and write. The paper points to potential uses in computer memory, quantum devices and more energy-efficient data centers, though the authors caution that the result covers a single material and that controlling altermagnetic order with light or electric fields — a prerequisite for any real device — remains a future step, not a finished one.
Independent physicists have pushed back on how novel the "third type" framing really is, noting that ferrimagnetism, a longstanding category combining unequal opposing spins, already complicates the simple two-class picture. Jost's team and other groups, including researchers at the Paul Scherrer Institute and the University of Nottingham, have spent the past two years racing to nail down experimental signatures of altermagnetism in different materials; this result is the latest entry in that case, not the first.