A team of researchers from the Hong Kong University of Science and Technology (HKUST) has achieved a major breakthrough in antiferromagnetism. In bridging the gap between theory and application, they first revealed the world’s first layered room-temperature antiferromagnetic metal with alternating magnetic sublattices. The research, led by Professor Liu and published in the journal Nature, reveals a new class of materials, known as altermagnets. This work not only elucidates a novel mechanism for spin splitting but brings a great opportunity to real applications of spintronics and valleytronics.
The study, released in Nature Physics, highlights the unique features of altermagnets. These materials allow for momentum-dependent spin splitting independent of spin-orbit coupling (SOC) and net magnetization. This unique property makes altermagnets emerge as nontraditional antiferromagnets, paving the road toward innovative (and improved) technologies of the future.
A New Class of Antiferromagnets
In 2024, Science magazine celebrated the discovery of these altermagnets as one of the 10 biggest breakthroughs. This honor highlights the pioneering impact that this research has made to the rapidly-expanding field of materials science. Altermagnets have a distinct magnetic structure that makes them operate efficiently even at room temperature. This feature enormously increases their real-world usefulness.
The research team, led by Professor Liu, determined a new mechanism of spin splitting. This mechanism is due to sublattices linked by symmetry through crystal structure which permits exchange coupling, leading to strong spin splitting effects. Scientists have recently found a new type of C-paired spin-valley locking (SVL) in these materials. This technological breakthrough would open up new pathways for creating next generation electronic devices.
“Suppression of intervalley scattering observed in the QPI pattern.” – Nature Physics
Key Experimental Findings
Theory contributions from Professor Liu’s group had laid the groundwork for experimental discoveries on two specific compounds, V2Te2O and V2Se2O, as early as 2021. Their initial modeling and experimental work showed that these materials could display the properties scientists were looking for in altermagnets. By experimental demonstration and first-principles calculations, researchers confirmed the realization of C-paired spin-valley locking. To do so, they employed leading edge methodologies, such as spin and angle-resolved photoemission spectroscopy (Spin-ARPES) and scanning tunneling microscopy/spectroscopy (STM/STS).
These combined techniques enabled a detailed investigation of the materials’ properties, experimentally validating theoretical predictions made previously. Most interestingly, the researchers noticed strong agreement between the experimental observations and first-principles calculations, offering compelling validation for their theoretical framework.
Implications for Future Technologies
The implications of this research are substantial. Altermagnets might be key in enabling next-gen devices based on new spintronic applications. Altermagnets offer a stronger, lighter, and more efficient alternative to traditional ferromagnets. They permit manipulating magnetic states much easier than traditional magnets without high energy.
Second, the discovery responds to the devastation wrought by alternative materials like MnTe2. This material, which exhibits a noncoplanar magnetic structure, was known to have a low critical temperature of 87 K. These restrictions introduced by MnTe2 significantly undermine its practical use in spintronic devices. The potential of altermagnets is nothing short of amazing, as they are stable at room temperature. In addition, they allow realizing large spin splitting.
