For almost 100 years, scientists believed there were only two main types of magnets.
One is the familiar ferromagnet, the kind found on refrigerators and in many electronic devices.
The other is the antiferromagnet, a less obvious type whose magnetic properties cancel out and remain hidden at larger scales.
In recent years, researchers have identified a possible third category known as altermagnets.
These unusual materials could combine some of the best features of both traditional types of magnets, potentially leading to faster, smaller, and more energy-efficient electronic devices.
Now, physicists at the University at Buffalo have proposed a new way to detect these elusive materials.
Their study, published in Physical Review Letters, describes a quantum sensing system that uses tiny defects inside diamonds to search for signs of altermagnetism.
Scientists are excited about altermagnets because they could dramatically improve the way information is stored and transmitted. However, researchers first need reliable methods to identify which materials truly belong to this new class.
The story of altermagnets began in 2019 when physicists studying a material called ruthenium dioxide noticed something strange. According to existing theories, the material should not have behaved the way it did. It appeared to have no overall magnetization, similar to an antiferromagnet, but it also showed behaviors normally associated with ferromagnets when electric current was applied.
This unexpected result led researchers to propose the idea of altermagnetism.
To understand why this matters, it helps to look at how ordinary magnets work. In ferromagnets, the spins of neighboring electrons point in the same direction. This alignment creates a magnetic field and makes the material easy to control, which is why ferromagnets are widely used in technology.
In antiferromagnets, neighboring electron spins point in opposite directions. Their magnetic effects cancel each other out, producing no overall magnetic field. Although harder to manipulate, antiferromagnets can switch states extremely quickly, making them attractive for future computing technologies.
Altermagnets appear to combine aspects of both. Their overall magnetism cancels out like an antiferromagnet, but their internal structure causes electrons to behave in ways that resemble ferromagnets. This combination could allow for faster information processing while maintaining efficient control over electronic properties.
To find more altermagnets, the University at Buffalo team proposes using diamonds containing special atomic defects. These defects occur when a nitrogen atom replaces a carbon atom and a nearby carbon atom is missing. Such imperfections are incredibly sensitive to magnetic activity in their surroundings.
The idea is to place a suspected altermagnetic material next to the diamond and observe how the defect’s magnetic signal changes. If the signal relaxes at different rates depending on its direction, it could reveal the unique magnetic patterns expected in altermagnets.
An important advantage of this approach is that it would disturb the material much less than many existing testing methods. This could help researchers observe the material’s natural behavior more accurately.
The proposed sensor currently exists only as a theoretical design, and experiments will be needed to prove that it works.
If successful, however, it could help scientists identify hundreds of possible altermagnetic materials and accelerate the development of next-generation electronics that are faster, smaller, and use less energy.
