SLAC Confirms Third Type of Magnetism After 90 Years of Two-Category Physics

For nearly nine decades, physicists organized magnetism into two columns: ferromagnetism, the kind that sticks to your refrigerator, and antiferromagnetism, where neighboring electron spins point in opposing directions and cancel each other out. A paper published in Science on October 29 says that taxonomy was incomplete.

<cite index="22-2,22-3">A team led by the U.S. Department of Energy's SLAC National Accelerator Laboratory has delivered what it describes as conclusive experimental proof of a third magnetic phase called altermagnetism.</cite> The underlying paper, authored by Daniel Jost and colleagues and titled "Chiral altermagnon in MnTe" (Science, Vol. 394, DOI: 10.1126/science.adv3196), focuses on manganese telluride, a material that physicists had long classified as antiferromagnetic.

The key to the confirmation was chirality, a structural property physicists sometimes call handedness. <cite index="29-5,29-6">The missing piece the team had been hunting for was experimental evidence of chirality in an altermagnetic candidate material. Chirality means a material cannot be superimposed on a mirror image of itself, just like a left hand cannot fit into a right-handed glove.</cite>

<cite index="36-7">The researchers scattered circularly polarized X-rays off manganese telluride at the European Synchrotron Radiation Facility and found that the material responded differently to left- versus right-handed beams, a chiral signal that should not exist in a conventional antiferromagnet.</cite> <cite index="36-8">The experiment was completed in 2024 and repeated in early 2025 with the same result.</cite> That replication matters. A single synchrotron measurement proving a new phase of matter would not hold up long in a skeptical field; running it twice, with consistent outcomes, is what moved the team from "evidence" to "conclusive proof" language.

<cite index="36-5,36-6">Altermagnetism, proposed as a theoretical concept in 2022, combines traits of both prior types. Like antiferromagnets, altermagnets have alternating up-down electron spins that cancel to zero net magnetization, but the crystal lattice around the "up" spins is rotated relative to the lattice around the "down" spins, breaking symmetry in a way that lets the material still generate spin-polarized currents.</cite>

That last property is what has the spintronics community paying attention. <cite index="24-7">Altermagnetism stands out because it can handle spin-polarized currents without getting thrown off by magnetic interference, which matters for things like quantum computers and next-generation memory systems.</cite> Conventional ferromagnets, which also generate spin-polarized currents, are vulnerable to stray magnetic fields that can corrupt stored data. Antiferromagnets are stable but notoriously hard to read out. Jost's team argues altermagnets avoid both problems.

<cite index="22-4">Future research will explore how altermagnetic states can be influenced and controlled using light and electricity to enhance their usefulness in spintronic solutions for quantum technologies, memory devices, and data centers.</cite> That's a long road. The team worked with manganese telluride specifically because its crystal structure made the chiral signal detectable; whether the same properties show up cleanly in other candidate altermagnets, and whether any of them can be integrated into real devices, are open questions the paper doesn't settle.

What the paper does settle, according to the authors, is the taxonomy question. <cite index="29-2,29-3">"In the past few years, scientists have observed phenomena that don't fit neatly into the ferromagnetism-antiferromagnetism dichotomy," said lead author Jost. "We believe our results provide robust experimental confirmation that this third phase -- altermagnetism -- is real."</cite>

That's a careful framing, and the right one. Experimental proof of a new magnetic phase is not the same as a working device. But for condensed-matter physicists who've spent years arguing over whether altermagnetism was a genuine phase or a theoretical convenience, the chiral signature in MnTe is a concrete result to build on.

Sources cited:
- Science (Jost et al., "Chiral altermagnon in MnTe") (https://www.science.org/doi/10.1126/science.adv3196)
- Nanowerk / SLAC press release (https://www.nanowerk.com/nanotechnology-news3/newsid=70510.php)
- Phys.org / SLAC National Accelerator Laboratory (https://phys.org/news/2026-10-altermagnetism-geometric-experimental-proof.html)
- ScienceDaily / SLAC (https://www.sciencedaily.com/releases/2026/11/261104012256.htm)
- daily.dev summary of SLAC findings (https://daily.dev/posts/slac-researchers-find-proof-of-altermagnetism-a-new-magnetic-phase-ki46tvoik)