Designing Spin Symmetry for Altermagnetism with Strong Magnetoelectric Coupling

Abstract Altermagnets, a recently identified class of collinear magnets, exhibit unique properties such as zero net magnetization and spin polarization dictated by lattice symmetry, making them a subject of intense research. In contrast to conventional strategies for inducing altermagnetism in antiferromagnets that rely on manipulating real‐space symmetry, this work introduces a novel and general approach to achieving altermagnetism by modulating spin‐space symmetry. Through a combination of tight‐binding models and first‐principles calculations, the microscopic origin of altermagnetism driven by spin‐space symmetry is uncovered, and the mechanism underlying enhanced spin splitting is identified. Furthermore, it is demonstrated that this spin‐space modulation can synergistically interact with ferroelectricity, enabling a spin symmetry‐dependent magnetoelectric coupling mechanism that is distinct from conventional multiferroics. This unique coupling is validated by the magneto‐optical Kerr effect, providing a robust theoretical foundation for the development of next‐generation spintronic devices that harness the potential of altermagnetism.