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Physicists have experimentally confirmed the existence of a new type of magnetism called altermagnetism. Studies conducted at the Swiss Light Source and later at Tohoku University show that certain materials can have no net magnetisation yet still display strong spin‑dependent effects. This discovery opens up possibilities for next‑generation spintronic devices and has been recognised as one of the scientific breakthroughs of 2024–25.
Background
Magnetic materials have long been classified into two main categories. Ferromagnets, such as iron, have electron spins that align in the same direction, producing a net magnetic field; these are the magnets that stick to a fridge. Antiferromagnets have spins that align in alternating directions, so their magnetic fields cancel and they show no net magnetisation. While antiferromagnets offer advantages for data storage—such as minimal interference between bits—their lack of strong spin‑dependent effects makes them less useful in devices. In 2019 theorists proposed the existence of materials whose spins alternate like antiferromagnets but whose crystal symmetry creates a special electronic structure that still exhibits strong spin polarisation. They named this predicted state altermagnetism.
Key characteristics of altermagnets
- Alternating spins with a twist: Like antiferromagnets, the spins point in opposite directions, resulting in zero net magnetisation. However, the way the atoms are arranged in the crystal means that the electronic bands split differently for up and down spins, leading to a phenomenon called alternating spin polarisation.
- Combining the best of both worlds: Altermagnets exhibit strong spin‑dependent properties similar to ferromagnets while having no net magnetic field like antiferromagnets. This eliminates cross‑talk between bits in spintronic devices while retaining useful magnetic effects.
- Experimental proof: Researchers confirmed altermagnetism in manganese telluride crystals using spin‑ and angle‑resolved photoemission spectroscopy. Later, scientists in Japan used a new optical method to reveal altermagnetic behaviour in an organic crystal, demonstrating that the phenomenon occurs in diverse materials.
- Technological promise: Because altermagnets can manipulate electron spins without producing stray magnetic fields, they hold potential for low‑energy memory and logic devices. They might also provide a platform for studying unconventional superconductivity.
Outlook
Altermagnetism is an emerging field in condensed‑matter physics. Researchers are now searching for more altermagnetic materials and exploring ways to harness their unique properties. The discovery underscores how fundamental science can lead to unexpected insights with practical applications.
Sources: Phys.org, ScienceDaily