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New form of magnetism discovered in common materials

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New form of magnetism discovered in common materials

Scientists have confirmed the existence of a strange new form of magnetism. Hiding right under our noses, the team says that “altermagnetism” can be found in everyday materials and could have major technological uses.

The most familiar form of magnetism – the kind that keeps your kids’ terrible artworks pinned to your fridge – is what’s called ferromagnetism. The effect is produced when the spins of the electrons in the material all spin in the same direction. Another major branch is known as antiferromagnetism, which arises when electron spins alternate direction from their neighbors. Other forms include diamagnetism, paramagnetism and ferrimagnetism, which are all born from different mechanisms.

But now, a brand new form of magnetism has been discovered. It’s been dubbed altermagnetism, and it features a weird mix of properties from other types of the phenomenon – its electrons spin in alternating directions, like antiferromagnets, which means it doesn’t produce magnetization. But the material’s energy bands also have alternating spins from neighboring bands.

Altermagnetism was first predicted in 2019, but has now been confirmed in experiments at the Swiss Light Source (SLS) synchrotron. The inaugural altermagnetic material is manganese telluride, which has long been considered an antiferromagnet, because its electron spins point in opposite directions and it doesn’t have a net magnetization. But in this case, the team peered closer using X-rays, and found that its electronic bands split into different spin states – a predicted feature of altermagnets.

A diagram illustrating the differences between the newly discovered altermagnetism, and the more conventional branches of ferromagnetism and antiferromagnetism

Libor Šmejkal

While other new sub-forms of magnetism have been discovered in recent years, altermagnetism is perhaps the broadest newcomer and could have the most useful applications, such as superconductivity and an emerging field of science called spintronics. In electronics, information is encoded into the charge of electrons, but spintronics also encodes data in their spin. Ferromagnets usually have the best properties for spintronics experiments, but the magnetic field they produce can interfere with neighboring electrons. Antiferromagnets thankfully don’t have net magnetism, so they could be easier to scale and more efficient – but they also have weaker spin effects to encode data into. Altermagnetic materials, however, could offer the best of both worlds – they have the strong spin effects, but without net magnetism. This exact combo was long assumed to be impossible.

“Altermagnetism is actually not something hugely complicated,” said Tomáš Jungwirth, principal investigator of the study. “It is something entirely fundamental that was in front of our eyes for decades without noticing it. And it is not something that exists only in a few obscure materials. It exists in many crystals that people simply had in their drawers. In that sense, now that we have brought it to light, many people around the world will be able to work on it, giving the potential for a broad impact.”

The research was published in the journal Nature.

Source: Paul Scherrer Institut



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