Structure, Control, and Dynamics of Altermagnetic Textures

Altermagnets are collinear magnetically ordered phases with zero net magnetization and alternating spin polarization. These emergent materials combine fast magnetic dynamics with large spin band splitting. Both effects arise from strong (non-relativistic) exchange interactions between local magnetic moments and electron spins. I will present a phenomenological theory of altermagnets that describes their unique magnetization dynamics and magnetic textures. Focusing on prototypical d-wave altermagnets such as RuO₂, we can intuitively explain the unique lifted degeneracy of their magnon spectra by the emergence of an effective, sublattice-dependent, anisotropic spin stiffness, which arises naturally from the phenomenological theory. 
I will discuss a symmetry-based approach to describe altermagnetic textures and dynamics using the altermagnet candidate Mn5Si3 as an example. The approach’s key point is an altermagnetic order parameter that formalizes the symmetry of the magnetic atoms’ local environment and enables the altermagnetic behavior to be distilled [1]. I will demonstrate how this concept enables us to reconstruct the equilibrium magnetic structure of Mn5Si3 from the field dependences of the anomalous Hall effect [2]–[4]. Finally, I will discuss the spin wave spectra and dynamics of the altermagnetic domain wall, focusing on a comparison between the altermagnetic and antiferromagnetic phases of the material.

[1]  O. Gomonay et al., “Structure, control, and dynamics of altermagnetic textures,” npj Spintronics, vol. 2, art. no. 35, Jul. 2024, doi: 10.1038/s44306-024-00042-3. 
[2]  J. Rial, et al., “Altermagnetic variants in thin films of Mn5Si3,” Phys. Rev. B, vol. 110, art. no. L220411, Dec. 2024, doi: 10.1103/PhysRevB.110.L220411. 
[3]  M. Leiviskä, et al., “Anisotropy of the anomalous Hall effect in thin films of the altermagnet candidate Mn5Si3,” Phys. Rev. B, vol. 109, art. no. 224430, Jun. 2024, doi : 10.1103/PhysRevB.109.224430.
[4]  R. Zarzuela, et al., “Transport theory and spin-transfer physics in 𝑑-wave altermagnets,” Phys. Rev. B, vol. 111, art. no. 064422, Feb. 2025, doi: 10.1103/PhysRevB.111.064422.