When physicist Jamir Marino peers into a tiny defect in a diamond, he’s not looking for sparkle—he’s hunting for a new kind of magnetism that could reshape electronics. At the University at Buffalo, Marino and his team have proposed a quantum sensing method that could finally confirm the existence of altermagnets, a mysterious class of magnetic materials first theorized just five years ago by Libor Šmejkal and Jairo Sinova at Johannes Gutenberg University of Mainz. For decades, scientists thought magnetism came in only two forms: ferromagnets, like the magnets on your fridge, and antiferromagnets, whose atomic spins cancel out and remain invisible to everyday observation. Altermagnets, however, blur the line—behaving like antiferromagnets in overall magnetization but mimicking ferromagnets in how their electrons respond to electric currents. This hybrid nature could unlock ultra-fast, energy-efficient computing, but only if researchers can reliably detect them.
The challenge lies in their subtlety. Altermagnets don’t produce a net magnetic field, making traditional detection methods nearly useless. That’s where the diamond comes in. The team’s technique centers on a nitrogen-vacancy (NV) center—a microscopic flaw in a diamond where a nitrogen atom replaces a carbon atom next to a missing one. These NV centers act as exquisitely sensitive magnetic sensors. By rotating the spin of the defect and measuring how quickly it relaxes in different directions, scientists can detect the unique, directional magnetic patterns that only altermagnets produce. Unlike other methods, this approach barely disturbs the material, preserving its natural state during measurement.
The implications are vast. Theoretical models suggest over 200 materials could be altermagnetic—more than double the known number of ferromagnetic substances. Ruthenium dioxide was the first candidate to show signs of this behavior, puzzling researchers when it responded to electric currents like a ferromagnet despite having no net magnetization. Now, with a tool that can probe these hidden spin arrangements, scientists may finally verify whether altermagnetism is as widespread and useful as predicted. “This could be the first building block of a new generation of experiments that determine whether a material is an altermagnet,” Marino says. As the search expands, this diamond-based sensor might become the standard for identifying one of the most promising frontiers in condensed matter physics—ushering in a new era of magnetic materials that are fast, stable, and efficient.