For the past few decades, the world of magnetism seemed scientifically simple. Materials fit into only two groups, ferromagnets and antiferromagnets—end of discussion. Over the past few years, though, that tidy picture has started to crack. Discussion of a third type of magnetism, dubbed “altermagnetism,” has grown from a whisper to a near-consensus. Still, one crucial piece of experimental proof was missing.
Now, thanks to scientists at the SLAC National Accelerator Laboratory at Stanford University, that final piece is finally in place.
First, a quick refresher. Ferromagnetism and antiferromagnetism, as their names suggest, are two sides of the same coin. In ferromagnets, all electronic spins point the same direction, creating an easily observable net magnetic field. The counterpart is the exact opposite: antiferromagnets containing alternating electronic spins that effectively cancel each other out, producing no net magnetic effect at all. Now, if you had to wager on where altermagnetism fits into this picture, somewhere between these two extremes might be your guess—and you’d be right.
“In the past few years, scientists have observed phenomena that don’t fit neatly into the ferromagnetism-antiferromagnetism dichotomy,” Daniel Jost, a SLAC associate scientist and lead author of the new study published in Science, said in a press statement. “Researchers have been compiling evidence of a third type of magnetism that bridges the qualities of these two classes. We believe our results provide robust experimental confirmation that this third phase—altermagnetism—is real.”
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