Antiferromagnetism

Researchers led by Rice University, the University of Minnesota, and the Paul Scherrer Institute - with additional collaborators at Kyung Hee University, the Gwangju Institute of Science and Technology (GIST), Lawrence Berkeley National Laboratory, Brookhaven National Laboratory, Myongji University, the University of West Bohemia, and the University of Illinois Urbana-Champaign - have found spin texture consistent with altermagnetism in ultrathin, epitaxially strained films of ruthenium dioxide (RuO₂), a material whose magnetic status has been debated for years.

Altermagnetism is a recently proposed third class of collinear magnetic order, alongside ferromagnetism and antiferromagnetism, in which compensated magnetic sublattices are related by rotation rather than by translation. That symmetry produces momentum-dependent spin splitting in a material's electronic structure even though it carries no net magnetization - a combination that could be useful for miniaturizing and improving RAM architecture in computers. RuO₂ was one of the first materials proposed as an altermagnetic candidate, but a long line of studies on its bulk and strain-relaxed thick-film forms - using x-ray diffraction, neutron diffraction, muon spin rotation, infrared spectroscopy, quantum oscillations, torque magnetometry and other probes - had converged on the conclusion that RuO₂ shows no magnetism at all, leaving the field in a persistent state of debate.

Researchers from Cornell University, together with collaborators from Columbia University and the University of Delaware, have demonstrated excitonic spin torque in the 2D magnetic semiconductor CrSBr. The work shows that excitons generated by light can directly drive and control magnetization dynamics, rather than only probing them, and establishes a new optical pathway to manipulate spins in magnetic semiconductors.

In the study, the team used ultrafast pump-probe measurements on the van der Waals antiferromagnet CrSBr. A short laser pulse creates a reservoir of tightly bound excitons in the material, and this exciton population exerts a spin torque on the underlying antiferromagnetic order. The torque has both damping-like and anti-damping-like components and drives the spins along a non-trivial trajectory on the magnetic energy landscape.

Researchers from the University of Tokyo, RIKEN and Tokyo Metropolitan University have demonstrated an ultrafast, energy-efficient nonvolatile switching device based on antiferromagnetic Mn₃Sn, achieving reliable operation in the picosecond regime with dramatically reduced power consumption.

The device is built on Mn₃Sn/tantalum heterostructures and utilizes spin–orbit torque (SOT) to switch the magnetic state using electrical pulses as short as 40 picoseconds. This represents a roughly 1,000× speed improvement over conventional nanosecond-scale switching, which has long been a practical limit in current CPU and GPU technologies due to rapidly increasing energy demands at higher speeds.

Researchers from The University of Tokyo, RIKEN Center for Emergent Matter Science (CEMS), Tokyo Metropolitan University, Karlsruhe Institute of Technology (KIT), Gdańsk University of Technology, High Energy Accelerator Research Organization, Japan Atomic Energy Agency, and additional institutes recently reported a metallic “twisted” antiferromagnet that realizes p‑wave magnetism and delivers a strong, easily readable spintronic signal. This material links a helical spin texture directly to charge transport, pointing toward faster, cooler, and more compact spin‑based memory and logic technologies.

In this compound, atomic magnetic moments do not all align in one direction as in a standard magnet; instead, they form a helix along a crystal axis, creating an antiferromagnetic “twisted” state with nearly zero net magnetization. This helical texture produces an odd‑parity (p‑wave) spin splitting of the conduction electrons, so electrons moving in different directions carry oppositely polarized spins without relying on strong electronic correlations.

Researchers from China's Hangzhou Dianzi University have developed an artificial intelligence-driven framework that could accelerate the discovery of antiferromagnetic materials for spintronics. Antiferromagnets (AFMs) are prized in advanced electronics because their alternating spin orientations cancel stray magnetic fields, creating fast, stable, and densely packable devices. However, their complex magnetic interactions and vast chemical possibilities have made systematic design extremely challenging.

The team’s approach combines a crystal diffusion variational autoencoder with data augmentation (CDVAE-DA), crystal graph convolutional neural networks (CGCNNs), a genetic algorithm (GA), and density functional theory (DFT) validation into a single, integrated pipeline. CDVAE-DA learns from tens of thousands of known crystal structures and then fine tunes its predictions on an AFM-specific dataset, producing novel, chemically valid candidates with over 90% composition accuracy. These structures are rapidly screened by CGCNN models, which assess three key properties: formation energy, total magnetic moment, and electronic band gap. Candidates meeting AFM-friendly criteria—stable energy, low net magnetization, and a targeted band gap range—are passed to the optimization stage.

A rare spin effect once thought confined to bulk crystals is now confirmed in ultrathin magnetic films. This effect, known as altermagnetism, arises in a special class of antiferromagnets where electronic bands split depending on electron momentum, despite the absence of net magnetization. Unlike ferromagnets, which produce disruptive stray fields, or conventional antiferromagnets, which often conceal useful spin properties, altermagnets combine stability with robust spin-split band structures - making them attractive for spin-based devices.

A recent study by scientists from Pennsylvania State University, University of California (Santa Barbara), University of Minnesota, National Institute of Standards and Technology, Lawrence Berkeley National Laboratory, SLAC National Accelerator Laboratory, Oakridge National Laboratory and Israel's Weizmann Institute of Science demonstrated this behavior in chromium antimonide (CrSb) thin films. 

Antiferromagnets are attracting growing attention as promising complements to conventional ferromagnets. While their properties have been extensively studied, clear demonstrations of their technological advantages have remained elusive. Now, researchers from Tohoku University, the National Institute for Materials Science (NIMS), and the Japan Atomic Energy Agency (JAEA) managed to provide compelling evidence of the unique benefits of antiferromagnets. Their recent study shows that antiferromagnets enable high-speed, high-efficiency memory operations in the gigahertz range, outperforming their ferromagnetic counterparts.

The team used the chiral antiferromagnet Mn₃Sn, whose spins form a non-collinear arrangement, as the medium for writing digital information. They fabricated a nanoscale Mn₃Sn dot device and successfully induced coherent rotation of its antiferromagnetic texture using electric currents. This enabled fast, high-fidelity control of spin ordering.

Researchers from Cornell University, Columbia University and Japan's National Institute for Materials Science have demonstrated direct electrical detection of antiferromagnetic resonance in structures on the few-micrometer scale using spin-filter tunneling in PtTe₂/bilayer CrSBr/graphite junctions in which the tunnel barrier is the van der Waals antiferromagnet CrSBr. 

Ferromagnetic materials have been in use in technologies like magnetic hard drives, magnetic random access memories and oscillators for many years. But antiferromagnetic materials, if only they could be harnessed, hold even greater potential: ultra-fast information transfer and communications at much higher frequencies. Now, the researchers' recent work is a step in that direction. Their work could be beneficial for both detecting and controlling the motion of spins within antiferromagnets using 2D antiferromagnetic materials and tunnel junctions.

Researchers at MIT, Università degli Studi "Gabriele d'Annunzio", Yale University, Drexel University, Rutgers University and University of Illinois Urbana-Champaign have demonstrated a new form of magnetism that could one day be harnessed to build faster, denser, and less power-hungry spintronic memory chips.

The new magnetic state is a hybrid of two main forms of magnetism: the ferromagnetism and antiferromagnetism. Now, the MIT team has demonstrated a new form of magnetism, termed “p-wave magnetism.”

In a recent study, researchers have discovered antiferromagnetism in a real Quasicrystal (QC). The team was led by Ryuji Tamura from the Department of Materials Science and Technology at Tokyo University of Science (TUS), along with Takaki Abe, also from TUS, Taku J. Sato from Tohoku University, and Max Avdeev from the Australian Nuclear Science and Technology Organization and The University of Sydney.

Quasicrystals are solid materials that exhibit an intriguing atomic arrangement. Unlike regular crystals, in which atomic arrangements have an ordered repeating pattern, QCs display long-range atomic order that is not periodic. Due to this 'quasiperiodic' nature, QCs have unconventional symmetries that are absent in conventional crystals. Since their Nobel Prize-winning discovery, condensed matter physics researchers have dedicated immense attention toward QCs, attempting to both realize their unique quasiperiodic magnetic order and their possible applications in spintronics and magnetic refrigeration.