The research team from CIC nanoGUNE’s Nanodevices Group, in collaboration with the Mesoscopic Physics Group at the Materials Physics Center (CFM) and research groups from Czechia, Germany and France, has experimentally demonstrated, for the first time, that an altermagnet can generate a spin current capable of carrying magnetic information. This finding is supported by the theoretical model of electronic transport developed by the CFM group. Altermagnets constitute a new class of materials that can generate such currents despite lacking the net magnetization characteristic of conventional magnets. The result experimentally confirms a prediction made a few years ago by research groups from Czechia and Germany, and represents a significant advance in the study of altermagnets and their potential for developing new information storage and processing technologies. The findings have been published in the prestigious journal Nature.
Altermagnets constitute 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 produces a net magnetization, responsible for the magnetic field we commonly associate with a magnet. This magnetization is also used to store information in the magnetic memories found in everyday devices such as hard drives, servers and magnetic stripe cards. In conventional antiferromagnets, by contrast, the magnetic moments point in opposite directions and cancel each other out, meaning that the material has no net magnetization, although it retains an internal magnetic order.
Although antiferromagnets have been known for approximately a century, a new class of materials with compensated magnetic moments—altermagnets—has only recently been identified. Like antiferromagnets, altermagnets have no net magnetization. “This magnetic order still has two possible states, but they cannot be distinguished from the outside because they do not generate a magnetic field: the information remains hidden inside the material. However, in these materials, the internal magnetic order does influence the behaviour of electrons. This interaction makes it possible to translate magnetic information into an electrical signal, opening up a way to access it,” says Fèlix Casanova, Ikerbasque Research Professor and leader of nanoGUNE’s Nanodevices Group.
To demonstrate this, the research team developed a nanodevice capable of extracting magnetic information from the altermagnet and transporting it to a detector. nanoGUNE’s expertise in fabricating devices at the nanoscale was key to this advance, as spin currents—which carry information associated with the orientation of electron spins—retain this information only over very short distances. “In the device we developed, the altermagnet and the detector are separated by just 300 nanometres, approximately one hundredth of the thickness of a human hair. When an electric current passes through the altermagnet, its internal magnetic order influences the behaviour of the electrons and generates a spin current that travels through a metallic channel to the detector, where it produces an electrical signal,” explains Jone Mencos, a researcher in nanoGUNE’s Nanodevices Group and first author of the paper. Subsequently, “the team reverses the material’s magnetic order using strong magnetic fields available in our laboratory and observes that the detected signal also reverses its sign. This correspondence confirms that the electrical signal is linked to the altermagnet’s internal magnetic information and rules out other effects present in the device as its cause,” adds the nanoGUNE researcher.
According to the researchers, altermagnets could pave the way for faster, more robust and denser magnetic memories. Because they have no net magnetization, these materials can reverse their magnetic order more quickly, are less sensitive to external magnetic fields that can erase conventional magnetic memories, and generate less interference between devices, potentially allowing more information to be stored in less space. “The next challenge will be to reverse their magnetic order using low-energy electrical pulses and make these devices work at room temperature,” says Fèlix Casanova.
Bibliographic reference
Jone Mencos, Antonin Badura, Eoin Dolan, Sebastian Beckert, Rafael González-Hernández, Nicolás Sigales, Tim Kokkeler, Ismaïla Kounta, Matthieu Petit, Charles Guillemard, Anna Birk Hellenes, Warlley Campos, Javier Rial, Dominik Kriegner, Vincent Baltz, Luis E. Hueso, Jairo Sinova, F. Sebastian Bergeret, Olena Gomonay, Tomáš Jungwirth, Libor Šmejkal, Lisa Michez, Helena Reichlova y Fèlix Casanova.
Time-reversal-symmetry-breaking spin injection from a compensated magnet
Nature (2026)
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