Researchers at the University of Nottingham have made a groundbreaking discovery with the identification of altermagnetism, marking the first conclusive evidence of this elusive third class of magnetism. Published on December 11, 2023, in the journal Nature, this finding could revolutionize the design of high-speed magnetic memory devices and address longstanding issues related to superconducting materials.
Altermagnetism has the potential to bridge the functionalities of the two well-established forms of magnetism: ferromagnetism and antiferromagnetism. According to Oliver Amin, a postdoctoral researcher on the study, "We have previously had two well-established types of magnetism, ferromagnetism, where the magnetic moments all point in the same direction, and antiferromagnetism, where neighboring moments point oppositely, akin to alternating colors on a chessboard."
Altermagnets operate under unique conditions. First theorized only last year, this new magnetic class has individual magnetic moments positioned to oppose their neighbors, but with slight twists, resulting in properties reminiscent of ferromagnetic materials. This combination offers promising advantages for developing magnetic memory technology, which relies on the manipulation of electron spins within electrical currents.
When it came to mapping the structure and properties of altermagnetic materials, the research team employed cutting-edge techniques, particularly photoemission electron microscopy. This approach allowed them to confirm the presence of altermagnetism within manganese telluride, a material previously thought to be antiferromagnetic. The research team, led by Professor Peter Wadley, reported the findings stating, "Different aspects of the magnetism become illuminated depending on the polarization of the X-rays we choose."
The discovery has significant ramifications for memory devices—particularly those operating at high speeds. Altermagnets can combine the speed and resilience characteristic of antiferromagnetic materials, alongside time reversal symmetry breaking found typically within ferromagnets. Alfred Dal Din, co-author and doctoral student, explained, "Altermagnets have the speed and resilience of an antiferromagnet, but they also have this important property of ferromagnets called time reversal symmetry breaking."
The explanation of time reversal symmetry can seem complex. To simplify, this property implies differences exist when observing systems of electrons moving forward and reversed in time. Amin elaborated, stating, "If you rewind time, you may think nothing changes; but because electrons possess both quantum spin and magnetic moments, reversing time actually alters the direction of travel, leading to observable differences."
With their research marks the advent of altermagnetic devices, the team could fabricate new memory technologies by manipulating the internal magnetic structures of these new materials through precisely controlled thermal cycling techniques. “We were able to form these exotic vortex textures, gaining more and more attention within spintronics as potential carriers of information,” Amin remarked.
The applications of altermagnetism stretch beyond just memory devices; the technology holds promise for improvements within superconductivity as well. Dal Din noted, "Altermagnetism will also help with the development of superconductivity... this class of magnetic material turns out to be this missing link in the puzzle of existing research."
This finding not only paves the way for new technologies but also uncovers significant insights within the broader field of physics and materials science. Researchers are now set on exploring how altermagnetism might exist across various materials, potentially leading to more practical applications and advancements.
Overall, the discovery of altermagnetism at the University of Nottingham signifies not only the advancement of knowledge within magnetism but also opens numerous avenues for practical innovation—especially as society continues to advance toward ever-faster and more reliable information technology. The researchers’ commitment to exploring this new frontier marks both the achievement of addressing previously held theories about magnetism and the beginning of promising developments based on those principles.