Electrical signals reveal hidden magnetic information in altermagnets for first time

Electrical signals reveal hidden magnetic information in altermagnets for first time Gaby Clark Scientific Editor Robert Egan Senior Editor Researchers have experimentally demonstrated, for the first time, that it is possible to obtain from an altermagnet a spin current that can transport magnetic information. This result is supported by the theoretical model of electron transport developed by the CFM group. Altermagnets are a new class of materials that, despite not exhibiting the net magnetization characteristic of conventional magnets, can generate this type of current. The result experimentally confirms a prediction made a few years ago by research groups in the Czech Republic and Germany, and represents an advance in the study of altermagnets and their potential for the development of new information storage and processing technologies. The results of this study have been published in the journal Nature. The team includes CIC nanoGUNE's Nanodevices Group, in collaboration with the Mesoscopic Physics Group of the Materials Physics Center (CFM) and research groups in the Czech Republic, Germany and France. Magnetic information hidden inside the material Altermagnets are a new class of magnetic materials. In conventional magnets, or ferromagnets, the magnetic moments of the atoms point in the same direction. The sum of these moments creates a net magnetization, which is responsible for the magnetic field we usually associate with a magnet, but which is also used as information in the magnetic memories we use daily in devices such as hard disk drives, servers and magnetic stripe cards. In conventional antiferromagnets, however, the magnetic moments point in opposing directions and cancel each other out, so the material does not exhibit net magnetization, though it does maintain an internal magnetic order. Although antiferromagnets have been known for almost a century, it was only recently that a new class of materials with compensated magnetic moments was identified: the altermagnets. As with antiferromagnets, altermagnets do not exhibit net magnetization. "This magnetic order still has two possible states, but it is indistinguishable from the outside as it does not generate a magnetic field; the information remains hidden inside the material. However, in these materials, the internal magnetic order affects the behavior of electrons. This interaction enables the magnetic information to be converted into an electrical signal, thus providing a way to access it," points out Fèlix Casanova, Ikerbasque research professor and leader of the Nanodevices Group at CIC nanoGUNE. Transporting a signal across 300 nanometers To demonstrate it, the research team developed a nanodevice that can extract the magnetic information from the altermagnet and transport it to a detector. CIC nanoGUNE's experience in manufacturing nanoscale devices has been key to this advance, since the spin currents—which transport information associated with the spin orientation of the electrons—retain this information only over very short distances. "In the device developed, the altermagnet and detector are separated by just 300 nanometers, approximately one-hundredth the thickness of a human hair. When an electric current passes through the altermagnet, its internal magnetic order affects the behavior of the electrons and generates a spin current that propagates through a metal conduit until it reaches the detector, where it produces an electrical signal," explains Jone Mencos, a researcher with the Nanodevices Group at CIC nanoGUNE and lead author of the work. Next, "the team reversed the magnetic order of the material using strong magnetic fields, available in our laboratory, and observed that the detected signal also changes direction. This correspondence confirms that the electrical signal is linked to the altermagnet's internal magnetic information and allows us to rule out the possibility that it is due to other effects in the device," adds the CIC nanoGUNE researcher. Room-temperature operation remains a challenge According to the research team, altermagnets could pave the way to faster, denser and more robust magnetic memories. Since there is no net magnetization, these materials can reverse their magnetic order more quickly, they are less sensitive to external magnetic fields that can erase conventional magnetic memories, and they generate less interference between devices, which would allow more information to be stored in less space. "The next challenge will be to reverse its magnetic order using low-energy electrical pulses and to make these devices function at room temperature," says Casanova. Publication details Jone Mencos et al., Time-reversal-symmetry-breaking spin injection from a compensated magnet, Nature (2026). DOI: 10.1038/s41586-026-11227-7 Journal information: Nature Provided by Elhuyar Fundazioa