Researchers at the Swiss Light Source (SLS) at the Paul Scherrer Insitute in Switzerland have discovered a new type of magnetism that has never been observed before. Called altermagnetism, this type of magnetism was confirmed through work conducted in collaboration with the Czech Academy of Sciences (CAS).
When speaking of magnets, one often thinks of things that stick readily to the fridge, scientifically known as ferromagnets. But about a century ago, humanity found another family of magnetic materials that did not display such behavior and called them antiferromagnets.
The difference in the material behavior boils down to the spontaneous arrangement of magnetic moments, also known as electron spins, in these materials. The spins are in the same direction as ferromagnets, which deliver the magnetic properties observed when closer to a metal surface. In antiferromagnets, the electron spins are in opposite directions and cancel the magnetism generated. This leads to the inability to stick to a fridge.
In altermagnetism, the electron spins are alternate, creating no net macroscopic magnetism. However, the electronic band structure has a strong spin polarization that can flip through the material’s energy bands. This is why the material has been dubbed an altermagnet.
How was it discovered?
In 2019, Tomas Jungwirth, a researcher at the Institute of Physics at the CAS, found a class of magnetic materials whose electron spins did not match those of ferromagnets or antiferromagnets. In 2022, together with researchers at the University of Mainz, Jungwirth theorized the existence of a new class of magnets.
During their research, the team found more than 200
materials ranging from insulators to semiconductors and even superconductors
that were probably candidates for altering magnets.
To confirm the existence of unique spin symmetry in these materials, the researchers teamed up with SLS in Switzerland. They used spin- and angle-resolved photoemission spectroscopy to visualize the electronic structures in materials.
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They tested manganese telluride, a two-element material conventionally classified as an antiferromagnet. However, the material displayed a splitting of electronic bands into two different states, much like a ferromagnet. This confirmed that the material was indeed an alter magnet.
Where will it be used?
The discovery of a third type of magnetic material could help deliver next-generation magnetic memory using spintronics. In conventional electronics, one makes use of the charge of electrons. However, in spintronics, the spin state of electrons is also used to store information.
The nascent field of computing has been using ferromagnets to develop such devices. However, the macroscopic magnetism displayed by the materials is a cause for concern since it can facilitate cross-talk between bits. Since altermagnets do not display net magnetism but have strong spin-dependent effects, they can serve as the ideal candidates for spintronics.
“Altermagnetism is actually not something hugely
complicated. It is something entirely fundamental that was in front of our eyes
for decades without noticing it,” said Jungwirth in a press release. “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.”
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