Spectroscopy of Altermagnetic Magnons

Objective

The magnetic properties of solids form the basis of many modern technologies, ranging from permanent magnets in motors to data storage. Among emerging applications, spintronics is a promising approach to classical computing at THz frequencies, offering miniaturization and improved energy efficiency. Altermagnets, a recently discovered third type of magnetic ordering, are a particularly promising platform for spintronics because altermagnetic magnons combine the key advantages of ferromagnetic and antiferromagnetic magnons. However, due to their only very recent experimental observation, our knowledge of altermagnetic magnons — and altermagnets more broadly — is limited. For instance, theoretically predicted magnon splitting has only been confirmed via inelastic neutron scattering (INS) in one material to date. To address this knowledge gap, I propose ALMAG – a systematic study of magnons in altermagnetic candidate systems using INS and resonant inelastic X-ray scattering (RIXS). These complementary techniques allow for the observation of magnon splitting via INS and the investigation of magnon chirality via polarization analysis on small samples or single magnetic domains using RIXS. ALMAG will leverage the new multiplexing neutron spectrometer BIFROST at the European Spallation Source (ESS), designed for small samples and complex environments, offering superior resolution and flux. As part of BIFROST’s early science program starting in fall 2026, ALMAG will contribute to its optimization and effective use. In the second phase, ALMAG will further expand our knowledge of altermagnets by exploring the tunability of altermagnetic magnons through the combination of high magnetic fields, hydrostatic and uniaxial pressure with INS and RIXS. Overall, ALMAG will confirm or rule out candidate systems, significantly advance our understanding of altermagnetic magnons, and assess their tunability – laying the groundwork for future spintronic technologies.