A team of physicists credited with identifying a third fundamental class of magnetism has been awarded one of the field’s major prizes, capping a rapid rise for an idea that was barely a few years old when experiments began confirming it.
For more than a century, textbooks have described magnetic materials in two broad families. In ferromagnets â the familiar fridge magnets, the magnets in motors and loudspeakers â the tiny magnetic moments carried by electrons all point the same way, producing a net magnetic field strong enough to stick to steel. In antiferromagnets, discovered in the mid-20th century and themselves the subject of a Nobel Prize, neighbouring moments point in opposite directions and cancel out, leaving a material that is magnetically ordered on the inside but shows almost no magnetism on the outside.
The newly recognised class, known as altermagnetism, sits awkwardly between the two â and behaves like neither. Like an antiferromagnet, an altermagnet has alternating up and down moments that cancel, so it produces essentially no stray magnetic field. But because of the way the atoms and their surrounding crystal environments are arranged, the symmetry of the material is broken in a subtler way. The result is that electrons travelling through an altermagnet feel a strong, direction-dependent magnetic influence, as if the material were a ferromagnet, even though it looks magnetically neutral from the outside.
That combination is unusual enough that many physicists were initially sceptical. The concept was set out theoretically in the early 2020s, drawing on symmetry analysis and computational predictions of which known compounds should display the effect. Within a short time, experimental groups using techniques such as photoemission spectroscopy â which maps the energy and momentum of electrons inside a crystal â reported signatures matching the predictions. The field expanded quickly, with research groups around the world hunting for new candidate materials and probing their properties.
The appeal is not purely intellectual. Magnetism underpins most of the world’s data storage, and the properties of altermagnets look attractive for a branch of electronics called spintronics, which aims to encode information in the spin of electrons rather than their charge. Ferromagnets are easy to read and write but their stray fields limit how densely devices can be packed, and they switch relatively slowly. Antiferromagnets are compact and can switch extremely fast, but their lack of external magnetism makes them hard to control and detect.
Altermagnets, in principle, could offer the best of both: the dense, fast, interference-free behaviour of antiferromagnets combined with the strong, readable electronic response associated with ferromagnets. Researchers have suggested applications ranging from faster, denser memory chips to new kinds of sensors, though practical devices remain some way off.
The prize recognition marks a notable milestone for a concept that moved from proposal to broad acceptance in an unusually short period â a reminder that even in a field as mature as magnetism, fundamental categories can still be revised. Much of the work ahead involves cataloguing which materials qualify, understanding how to switch them reliably, and determining whether their theoretical advantages survive the transition to real-world engineering.
For now, the award underlines a shift in how physicists classify magnetic matter. After decades in which two categories sufficed, students may soon be learning about three. Read More
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