Condensed Matter Journal Club: Signatures of spin-phonon coupling in altermagnetic MnF2

Abstract: Altermagnetism is a recently defined class of magnetic order that resembles antiferromagnetism but is driven by underlying multipolar order. In many materials, this order arises from a combination of magnetic dipole and charge octupole moments. As a result, altermagnets are predicted to exhibit unique phenomena, including chiral magnon splitting, spin-split Fermi surfaces, and linear piezomagnetism. Here, I present evidence of strong spin–lattice coupling in MnF₂, a recently confirmed altermagnet. Specifically, our inelastic x-ray scattering (IXS) spectra show a distinctive quasielastic shift that peaks as the magnetic transition is approached. Phenomenological modeling within a Landau–Ginzburg framework points to two possible microscopic origins for this shift: piezomagnetism or magnetostriction. I will discuss how each coupling might arise from the underlying symmetry and identify the most likely mechanism responsible for this pronounced spin–lattice effect.