Diamond-Based Quantum Sensor Proposed to Detect Altermagnets

Scientists have introduced a quantum sensing technique that utilizes defects in diamonds to detect altermagnets, an emerging category of magnetic materials exhibiting unusual magnetic behaviors.

For nearly a century, only two primary magnet types were recognized. Altermagnets, identified more recently, present a novel magnetic class with potential applications in faster and more energy-efficient electronics.

The University at Buffalo researchers developed a theoretical approach where a suspected altermagnetic sample is placed adjacent to a diamond containing a highly sensitive magnetic defect. Monitoring the relaxation of this defect's magnetic signal over time could reveal the distinct magnetic signature characteristic of altermagnets.

Jamir Marino, PhD, assistant professor in the UB Department of Physics, College of Arts and Sciences, stated, “This could be the first building block of a new generation of experiments that determine whether a material is an altermagnet.” He emphasized the need for experimental confirmation to verify the theoretical predictions about altermagnets' behavior.

Marino collaborated with Libor Šmejkal and Jairo Sinova from Johannes Gutenberg University of Mainz, who initially proposed the altermagnet concept. Sinova noted that this sensing method could become a vital tool for investigating candidate altermagnetic materials, offering benefits over traditional techniques by detecting subtle directional magnetic patterns without significantly disturbing the material.

Characteristics of Altermagnets Compared to Other Magnets

Conventional ferromagnets, such as those used on refrigerator magnets, have electron spins aligned uniformly, creating a controllable magnetic field crucial for computer memory. Antiferromagnets, in contrast, have neighboring electron spins oriented oppositely, canceling out overall magnetism but enabling faster state switching, which is promising for future electronics.

Altermagnets merge features of both types. Despite lacking net magnetization like antiferromagnets, their crystal structure induces electron behaviors typical of ferromagnets. This combination could facilitate quicker information processing and transmission with reduced energy consumption.

Marino explained, “That arrangement allows altermagnets to combine the rapid switching behavior of antiferromagnets with some of the more easily controllable electronic properties of ferromagnets.”

Origins and Identification of Altermagnets

The concept of altermagnetism arose in 2019 after Mainz researchers observed unexpected behavior in ruthenium dioxide. Although calculations indicated no overall magnetization, the material exhibited ferromagnetic-like properties when subjected to an electric current, prompting the proposal of a new magnetic material category.

Subsequent experimental studies have detected altermagnetic signs in various materials, with theoretical models predicting over 200 potential candidates—exceeding twice the number of known ferromagnetic materials.

Diamond Defects as Quantum Sensors

To accelerate the discovery of altermagnets, Marino’s team proposed a quantum sensing system based on a specific diamond defect formed by substituting one carbon atom with nitrogen and creating a neighboring vacancy. These defects are highly sensitive to nearby magnetic activity.

The method involves rotating the defect’s magnetic spin in different directions and measuring its relaxation rate. Direction-dependent relaxation changes could indicate the complex magnetic patterns predicted for altermagnets. This approach also minimizes disturbance to the material under study, preserving its natural behavior.

Marino remarked, “You don’t want your measurement to strongly perturb the material you’re studying because it can become harder to tell whether you’re seeing the material’s natural behavior or behavior caused by the experiment.”

Next Steps and Potential Impact

Currently, the sensing technique remains a theoretical proposal supported by advanced quantum simulations. Laboratory experiments are necessary to confirm its effectiveness in identifying altermagnets within actual materials.

Researchers anticipate that this tool could be instrumental in transitioning altermagnets from theoretical concepts to practical electronic applications. Marino stated, “Efficiently identifying altermagnetic materials is a crucial step toward one day actually using them in electronics.” He added that altermagnets could significantly improve information transport efficiency, enabling smaller, less power-intensive technologies.

The study, titled “Quantum Impurity Sensing of Altermagnetic Order,” was published on April 8, 2026, in Physical Review Letters. Co-authors include Hossein Hosseinabadi, PhD, now a postdoctoral scholar at the Max Planck Institute for the Physics of Complex Systems, and V. A. S. V. Bittencourt of the University of Strasbourg/Max Planck Institute for the Science of Light. The research received support from the German Research Foundation.