New Physical Phenomenon: Altermagnetism
noep writes:
There is now a new addition to the magnetic family: thanks to experiments at the Swiss Light Source SLS, researchers have proved the existence of altermagnetism:
Altermagnets have a special combination of the arrangement of spins and crystal symmetries. The spins alternate, as in antiferromagnets, resulting in no net magnetisation. Yet, rather than simply cancelling out, the symmetries give an electronic band structure with strong spin polarization that flips in direction as you pass through the material's energy bands -- hence the name altermagnets. This results in highly useful properties more resemblant of ferromagnets, as well as some completely new properties.
Spintronics has promised to revolutionise IT. Typically, ferromagnets have been used as they offer highly desirable, strong, spin-dependent physical phenomena. Yet the macroscopic net magnetisation that is useful in so many other applications poses practical limitations on the scalability of these devices as it causes crosstalk between bits. Instead, Antiferromagnets have been investigated for spintronics, as they have no net magnetisation and thus offer ultra-scalability and energy efficiency. However, the strong spin-dependent effects are lacking, again hindering their practical applicability.
Enter altermagnets with the best of both: zero net magnetisation together with the coveted strong spin-dependent phenomena typically found in ferromagnets -- merits that were regarded as principally incompatible.
The researchers believe that this new fundamental discovery in magnetism will enrich our understanding of condensed-matter physics, with impact across diverse areas of research and technology. As well as its advantages to the developing field of spintronics, it also offers a promising platform for exploring unconventional superconductivity, through new insights into superconducting states that can arise in different magnetic materials.
"Altermagnetism is actually not something hugely complicated. It is something entirely fundamental that was in front of our eyes for decades without noticing it," says Jungwirth. "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."
Original Publications: Altermagnetic Lifting of Kramers spin degeneracy (J. Krempasky, L. mejkal, S. W. D'Souza, M. Hajlaoui, G. Springholz, K. Uhliova, F. Alarab, P. C. Constantinou, V. Strokov, D. Usanov, W. R. Pudelko, R. Gonzalez-Hernandez, A. Birk Hellenes, Z. Jansa, H. Reichlova, Z. oba, R. D. Gonzalez Betancourt, P. Wadley, J. Sinova, D. Kriegner, J. Minar, J. H. Dil, T. Jungwirth) Nature, 14 February 2024
DOI: 10.1038/s41586-023-06907-7
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