UB Physicists Propose New Way to Detect Altermagnets, the "Third Class" of Magnetic Materials
A novel, non-invasive quantum sensing technique could simplify the identification of altermagnets, a recently discovered class of magnetic materials that combine the best properties of ferromagnets and antiferromagnets.
"This could be the first building block of a new generation of experiments that determine whether a material is an altermagnet." – Jamir Marino, University at Buffalo
The Challenge: A New Kind of Magnetism
For decades, physicists classified magnetic materials into two categories:
- Ferromagnets (like refrigerator magnets) have aligned electron spins, creating a strong, net magnetic field.
- Antiferromagnets have opposing spins that cancel out, resulting in zero net magnetism but enabling faster switching for potential electronic applications.
In 2019, a third class was theoretically proposed: altermagnets. Based on calculations on ruthenium dioxide, these materials exhibit zero net magnetization (like antiferromagnets) but display ferromagnet-like electronic behavior when an electric current is applied.
Theoretical predictions suggest more than 200 materials could be altermagnetic—more than twice the number of known ferromagnetic materials. Experimental signatures have been observed in only a handful of them, making a reliable detection method crucial.
A Diamond-Based Quantum Sensor
Marino and his team have proposed a quantum sensing system that could change this.
- The setup: Place a suspected altermagnet next to a diamond with a nitrogen-vacancy (NV) defect.
- The science: By measuring how the defect's magnetic signal relaxes in different directions, researchers can detect the unique spin dynamics of an altermagnet.
- The advantage: The method is less invasive than existing techniques, minimizing perturbation of the material under study.
The research, published in Physical Review Letters, was supported by the German Research Foundation.
Why It Matters
"Altermagnets could completely revolutionize the way we transport information." – Jamir Marino, University at Buffalo
Altermagnets are considered a potential game-changer for spintronics—a next-generation electronics that uses electron spin rather than charge to process information. They could combine the fast switching speeds of antiferromagnets with the controllable electronic properties of ferromagnets.
Jairo Sinova, a physicist at Johannes Gutenberg University Mainz, added: "This sensing technique could become a very important tool for exploring candidate altermagnetic materials."
Next Steps
The sensing system currently exists only in theory, developed using advanced quantum dynamics models. Experimental confirmation is required to validate whether the approach works as predicted.
If successful, this technique could accelerate the discovery of new altermagnetic materials, paving the way for practical applications in the future.