Amazing stuff!
"The experimental proof of a third branch of magnetism, termed altermagnetism, was made at the Swiss Light Source SLS ...
Altermagnets have a special combination of the arrangement of spins and crystal symmetries. The spins alternate, as in antiferromagnets, resulting in no net magnetization. Yet, rather than simply canceling 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 to ferromagnets, as well as some completely new properties. ..."
Altermagnets have a special combination of the arrangement of spins and crystal symmetries. The spins alternate, as in antiferromagnets, resulting in no net magnetization. Yet, rather than simply canceling 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 to ferromagnets, as well as some completely new properties. ..."
From the abstract:
"Lifted Kramers spin degeneracy (LKSD) has been among the central topics of condensed-matter physics since the dawn of the band theory of solids. It underpins established practical applications as well as current frontier research, ranging from magnetic-memory technology to topological quantum matter. Traditionally, LKSD has been considered to originate from two possible internal symmetry-breaking mechanisms. The first refers to time-reversal symmetry breaking by magnetization of ferromagnets and tends to be strong because of the non-relativistic exchange origin. The second applies to crystals with broken inversion symmetry and tends to be comparatively weaker, as it originates from the relativistic spin–orbit coupling (SOC). A recent theory work based on spin-symmetry classification has identified an unconventional magnetic phase, dubbed altermagnetic, that allows for LKSD without net magnetization and inversion-symmetry breaking. Here we provide the confirmation using photoemission spectroscopy and ab initio calculations. We identify two distinct unconventional mechanisms of LKSD generated by the altermagnetic phase of centrosymmetric MnTe with vanishing net magnetization. Our observation of the altermagnetic LKSD can have broad consequences in magnetism. It motivates exploration and exploitation of the unconventional nature of this magnetic phase in an extended family of materials, ranging from insulators and semiconductors to metals and superconductors, that have been either identified recently or perceived for many decades as conventional antiferromagnets."
Altermagnetism proves its place on the magnetic family tree (Paul Scherrer Institute) 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. The experimental discovery of this new branch of magnetism is reported in Nature and signifies new fundamental physics, with major implications for spintronics.
Altermagnetic lifting of Kramers spin degeneracy (open access)
Fig. 1: Illustration of weak and strong altermagnetic LKSD
Altermagnets have a special combination of the arrangement of spins and crystal symmetries. In both altermagnets (right) and antiferromagnets (centre), the spins alternate, giving a vanishing net magnetisation. However, in altermagnets the spins are connected by rotational symmetry whilst in antiferromagnets, they are connected by translation or inversion symmetry. In ferromagnets (left), spins align giving net macroscopic magnetisation.
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