Physics Sorted Magnets into Two Bins for a Century. The Third Bin Has 200 Entries.

For nearly a century, physicists sorted the magnetic world into two bins: ferromagnets (your refrigerator door, your compass needle) and antiferromagnets (the quiet ones, their magnetism locked away at the atomic scale). A third type, recognized only in the past decade, appears to draw on the strengths of both, and it goes by the name altermagnet. The appeal is practical: materials in this category could one day underpin electronics that run faster and consume far less power. The problem is that confirming whether a material actually belongs in this new category has been slow, expensive work. A team at the University at Buffalo thinks a flawed diamond might solve that.

Physicists at the University at Buffalo have put forward a quantum sensing scheme that could take much of the difficulty out of spotting these materials. The approach is theoretical for now: it involves watching how a candidate material perturbs a microscopic magnetic flaw inside a nearby diamond, and reading that disturbance for the signatures of altermagnetism.

The flaw in question is a nitrogen-vacancy center: a point in the crystal where a nitrogen atom sits beside an absent carbon, producing a structure that is exquisitely sensitive to surrounding magnetic fields. In the proposed experiment, the defect's magnetic spin would be oriented along multiple axes, with researchers tracking the rate at which it returns to its baseline state. Directional differences in that decay rate would serve as evidence of the elaborate spin geometry that distinguishes altermagnets from the rest.

The motivation for a faster detection tool comes down to numbers. Computational models have flagged more than 200 candidate materials as potentially altermagnetic, a tally that already exceeds twice the known count of ferromagnets, yet nearly all of those candidates remain experimentally unverified. The diamond-based method would also be considerably less invasive than most of the probing techniques currently in use.

The technique is still theoretical. Lead researcher Jamir Marino has argued that altermagnets hold the potential to fundamentally reshape how information moves through electronic systems, but that realizing this potential requires experiments capable of both identifying the materials and verifying that they behave in line with theoretical predictions.

Two categories of magnets held for a hundred years. We now have a way to detect altermagnets, which hold promise for improving electronics technology.

Read the full story at Phys.org, May 29, 2026

Hot Take: A century of assuming magnetism came in two flavors, and the correction arrives via a deliberately broken gemstone and a physicist measuring how fast something stops spinning.