#altermagnetism

A tiny diamond defect could reveal a mysterious new kind of magnetism

A diamond-based quantum sensor could help unlock a mysterious new class of magnets that may power the next generation of ultra-efficient electronics.

For decades, scientists recognized only two major types of magnets. One is the familiar ferromagnet, the kind found in refrigerator magnets and countless everyday devices. The other is the antiferromagnet, whose magnetic properties are hidden at the atomic level but have attracted growing interest because of their potential use in advanced technologies. More recently, researchers identified a third category known as altermagnets. First proposed within the last decade, these materials may combine some of the most useful characteristics of both ferromagnets and antiferromagnets, potentially opening the door to faster, more energy-efficient electronics.

Altermagnetism in RuO₂ thin films: A new magnetic material for the AI era

A research team has demonstrated that thin films of ruthenium dioxide (RuO₂) exhibit altermagnetism—the defining property of what is now recognized as the third fundamental class of magnetic materials. Altermagnets have the potential to overcome limitations associated with current magnetic random access memory using conventional ferromagnets and are attracting attention as promising materials for next-generation high-speed, high-density memory devices. In addition to identifying RuO₂ as a strong candidate for such applications, the study also highlights the possibility of enhancing its functionality through control of crystallographic orientation. The research findings are published in Nature Communications.

Spin Supercurrents in Superconducting Altermagnets

Materials from a new class of magnets could host permanent dissipationless spin currents when they enter a superconducting state. [...] Superconductors are famous for transporting electric charge with zero resistance. This ability underpins technologies such as MRI scanners, quantum computers, and sensitive magnetometers known as superconducting quantum interference devices. However, in the field of spintronics—which seeks to process information using electron spin rather than charge—achieving a similar long-range dissipationless transport has remained elusive. In ordinary metals, electron spins are highly susceptible to scattering and spin-orbit coupling, both of which cause spin currents to decay over short distances. Although research in superconducting spintronics based on ferromagnets has made progress [1, 2], ferromagnets produce stray magnetic fields that interfere with external circuit elements, and their internal magnetic fields tend to destroy superconductivity. Now Kyle Monkman of the University of British Columbia in Canada and his colleagues have proposed a novel path to dissipationless spin transport [3]. They predict that a class of materials known as superconducting altermagnets can naturally generate and carry net spin supercurrents. Remarkably, these currents can propagate even in the presence of spin-orbit coupling and magnetic disorder.

Confirming altermagnetism in an abundant mineral

Also known as magnetoelectronics, spintronics rely on electron spin rather than electron charge, as found in traditional electronics. Although spintronics is still an emerging field, spintronic technologies are already found in hard disk drives and giant magnetoresistance sensors used in industrial and automotive applications. Once the right foundational materials are discovered and verified, including economical materials for altermagnets, spintronics could advance technologies from wireless communication to quantum computing. Researchers using neutrons at the Department of Energy's Oak Ridge National Laboratory's Spallation Neutron Source (SNS) discovered that hematite, essentially rust, can help design energy-efficient spintronics.

Reversible spin splitting effect achieved in altermagnetic RuO₂ thin films

A research team affiliated with UNIST has made a advancement in controlling spin-based signals within a new magnetic material, paving the way for next-generation electronic devices. Their work demonstrates a method to reversibly switch the direction of spin-to-charge conversion, a key step toward ultra-fast, energy-efficient spintronic semiconductors that do not require complex setups or strong magnetic fields. Led by Professor Jung-Woo Yoo from the Department of Materials Science and Engineering and Professor Changhee Sohn from the Department of Physics at UNIST, the team has experimentally shown that within the altermagnetic material ruthenium oxide (RuO₂), the process of converting spin currents into electrical signals can be precisely controlled and flipped at will. This breakthrough is expected to accelerate the development of low-power devices capable of processing information more efficiently than current technologies. The study is published in the journal Nano Letters.

New third class of magnetism could transform digital memory: Experiment bridges theory and real-life realization

A new class of magnetism called altermagnetism has been imaged for the first time in a new study. The findings could lead to the development of new magnetic memory devices with the potential to increase operation speeds of up to a thousand times. Altermagnetism is a distinct form of magnetic order where the tiny constituent magnetic building blocks align antiparallel to their neighbors but the structure hosting each one is rotated compared to its neighbors. Scientists from the University of Nottingham's School of Physics and Astronomy have shown that this new third class of magnetism exists and can be controlled in microscopic devices. The findings have been published in Nature. Professor Peter Wadley, who led the research, explains, "Altermagnets consist of magnetic moments that point antiparallel to their neighbors. However, each part of the crystal hosting these tiny moments is rotated with respect to its neighbors. This is like antiferromagnetism with a twist. But this subtle difference has huge ramifications."

Physicists uncover a metallic altermagnet with d-wave spin splitting at room temperature

For many years, physics studies focused on two main types of magnetism, namely ferromagnetism and antiferromagnetism. The first type entails the alignment of electron spins in the same direction, while the latter entails the alignment of electron spins in alternating, opposite directions. Yet recent studies have discovered a new kind of magnetism, referred to as altermagnetism, which does not fit into either of the previously identified categories. Altermagnetism is characterized by the breaking of time-reversal symmetry (i.e., the symmetry of physical laws when time is reversed) and spin-split band structures, in materials that retain a zero net magnetization.

Researchers propose a simple magnetic switch using altermagnets

Controlling magnetism in a device is not easy; unusually large magnetic fields or lots of electricity are needed, which are bulky, slow, expensive and/or waste energy. But that looks soon to change, thanks to the recent discovery of altermagnets. Now scientists are putting forth ideas for efficient switches to manage magnetism in devices. Magnetism has traditionally come in two varieties: ferromagnetism and antiferromagnetism, based on the alignment (or not) of magnetic moments in a material. Early last year, physicists announced experimental evidence for a third variety of magnetism: altermagnetism, a different combination of spins and crystal symmetries. Researchers are now learning how to tune altermagnets, bringing science closer towards practical applications.