Magnetism, one of the fundamental forces of nature, has long been classified into two primary categories: ferromagnets and antiferromagnets. Ferromagnetic materials, such as iron, exhibit a strong and persistent magnetization, where atomic magnetic moments align in the same direction. On the other hand, antiferromagnets exhibit a state where neighboring atomic moments cancel each other out, resulting in no net magnetization. This clear dichotomy, however, has recently been challenged with the discovery of a new class of materials—altermagnets—that blur the lines between these traditional magnetic phases. This breakthrough opens up new possibilities for the development of spintronic devices and other cutting-edge technologies.
What Makes Altermagnets Unique?
Altermagnets represent a class of magnetic materials that, at first glance, appear to share characteristics with both ferromagnets and antiferromagnets. Like antiferromagnets, altermagnets have no net magnetization because their atomic magnetic moments cancel each other out. However, similar to ferromagnets, altermagnets break spin degeneracy, which is the energy equivalence between spin-up and spin-down electrons. This characteristic has significant implications for the development of materials that can generate and manipulate spin currents, which is crucial for the emerging field of spintronics—a technology that exploits both the spin and charge of electrons for storing, transferring, and processing information.
Altermagnets stand out because they combine the best features of both ferromagnets and antiferromagnets. They exhibit spin polarization (a hallmark of ferromagnetic materials), but without the associated issues of stray fields, which are typical of ferromagnets. In addition, they possess the advantageous dynamic properties of antiferromagnets, such as the ability to manipulate magnon dynamics in the terahertz range.
The Race to Discover Layered Altermagnets
The significance of altermagnets has not gone unnoticed by researchers. Over the last few years, a number of materials with the potential to be altermagnets have been identified, including compounds such as MnTe, CrSb, and Mn5Si3. However, most of these materials have a three-dimensional (3D) crystal structure, which limits their practical applications, particularly in the realm of spintronics. In contrast, layered materials, particularly two-dimensional (2D) materials, offer a wealth of advantages, including the ability to scale down to nanoscale devices and the potential to realize novel quantum phases.
The promise of 2D materials has fueled intense research efforts, as scientists search for layered altermagnets that could generate non-collinear spin currents. These types of spin currents are important for manipulating electron spins in a controlled manner, which is critical for future spintronic devices. In a groundbreaking paper published in Nature Physics, researchers from Songshan Lake Materials Laboratory, Southern University of Science and Technology, and the Hong Kong University of Science and Technology outlined their success in realizing a room-temperature metallic altermagnet, a material with a layered structure that demonstrates the desired properties for spin current generation.
A Breakthrough Material: Rb1-δV2Te2O
The research team led by Chaoyu Chen set out to create a layered altermagnet that could produce non-collinear spin currents at room temperature. Their focus was on a compound known as Rb1-δV2Te2O, which belongs to a class of materials predicted to exhibit the characteristics of altermagnets. This compound features a layered crystal structure, which distinguishes it from earlier altermagnet candidates that lacked the necessary two-dimensional properties.
To confirm that Rb1-δV2Te2O exhibited the necessary magnetic properties, the team began by measuring its magnetic susceptibility, a technique that helps determine the material’s response to an external magnetic field. Their findings confirmed that the material demonstrated room-temperature magnetic order—a key requirement for practical applications. Next, the researchers used angle-resolved photoemission spectroscopy (ARPES), a powerful technique for probing the electronic structure of materials, to show that the material’s band structure exhibited spin splitting—an indication of the spin polarization typically seen in ferromagnetic materials.
To further validate their findings, the researchers employed spin-resolved ARPES to directly measure the spin polarization of the material’s electronic structure. These measurements confirmed that Rb1-δV2Te2O was indeed spin-polarized, demonstrating the key feature of altermagnetic materials. Additionally, the team used scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) to observe the scattering of electrons between two opposite spins in Rb1-δV2Te2O. Remarkably, they found that this scattering was “forbidden”, meaning that electrons with opposite spins could not scatter between each other. This unique feature is a hallmark of altermagnets and is crucial for enabling the generation of non-collinear spin currents.
Applications in Spintronics and Beyond
The discovery of a layered altermagnet with the ability to generate non-collinear spin currents at room temperature is a breakthrough with profound implications for the future of spintronic devices. Spintronics relies on the manipulation of electron spins to store and process information. By harnessing both the charge and the spin of electrons, spintronic devices can offer advantages over traditional electronic devices, including higher speed, lower power consumption, and enhanced storage capacity.
One of the key advantages of Rb1-δV2Te2O is its ability to combine the best features of both ferromagnetic and antiferromagnetic materials. Unlike ferromagnets, Rb1-δV2Te2O does not suffer from the problem of stray fields, which can interfere with neighboring devices and lead to unwanted magnetic interactions. At the same time, it exhibits spin polarization and other key properties of ferromagnets, such as anomalous Hall transport and spin-splitting torque.
Moreover, the layered nature of Rb1-δV2Te2O opens up even more possibilities for quantum materials. The material could potentially be used to explore novel quantum phases, such as topological superconductivity, Chern insulators, and axion insulators—all of which have applications in quantum computing and other advanced technologies. The 2D nature of the material also makes it ideal for integration with other 2D materials like graphene and transition metal dichalcogenides, which could be used to engineer new superconducting and magnetic phases via proximity effects or by applying external strain or gating.
The versatility of this material extends beyond spintronics. Its potential to form twisted superlattices, where the electronic properties are tuned by changing the relative twist angle between adjacent layers, could lead to the discovery of entirely new quantum phenomena. Additionally, the ability to manipulate the material’s electronic properties via external means—such as strain or electrical gating—makes it a promising candidate for use in next-generation electronic and optoelectronic devices.
Looking Ahead: The Future of Altermagnets
The work by Chen and his colleagues has opened up an exciting new avenue for research in quantum materials. Their discovery of a room-temperature layered altermagnet could pave the way for the development of spintronic devices with unprecedented capabilities. The next step for the team is to fabricate spin transport devices based on Rb1-δV2Te2O and directly measure the spin current, which will provide valuable insights into the practical applications of this material in spintronics.
Furthermore, the success of this research could inspire other scientists to explore and engineer layered altermagnets with different compositions and properties, ultimately leading to the discovery of new materials that can be used in a wide range of technological applications.
In conclusion, the discovery of layered altermagnets marks a significant milestone in the field of quantum materials and spintronics. With their unique ability to combine the properties of both ferromagnets and antiferromagnets, these materials hold the potential to revolutionize the way we think about and use magnetic materials in future technologies. The journey of altermagnets has only just begun, and their full potential is yet to be realized.
Reference: Fayuan Zhang et al, Crystal-symmetry-paired spin–valley locking in a layered room-temperature metallic altermagnet candidate, Nature Physics (2025). DOI: 10.1038/s41567-025-02864-2. On arXiv: DOI: 10.48550/arxiv.2407.19555