Resonance-induced giant chiral magnonic splitting in rutile structure-based altermagnets

Altermagnets (AMs) exhibit unusual spin splitting in electronic structures and chirality splitting in magnonic spectra even without spin-orbit coupling, positioning them as promising spintronic materials. Rutile-structured AM candidates like RuO₂ were initially considered as prototypical AMs with large splittings. However, recent experiments indicate bulk RuO₂ is likely nonmagnetic, leaving direct confirmation of AM in rutile phase elusive due to scarce suitable materials. Employing first-principles calculations, we explore a class of rutile-structured altermagnets: transition metal difluorides series (TMF₂). Among these candidates, we find that CuF₂ exhibits large chiral splitting in its magnon spectrum. We attribute this chirality splitting to the strong super-superexchange interaction between magnetic entities separated by two nonmagnetic ligands. These findings suggest a possible route for experimental realization of AM in the rutile phase and provide insights into the critical interplay between orbital, spin, and lattice degrees of freedom in shaping unique properties of altermagnets.