Minimal models for altermagnetism

Niels Bohr Institute

Altermagnetism is a new class of magnetic order distinct from conventional ferromagnetism and antiferromagnetism. In this talk I will provide a brief introduction to altermagnetism followed by a discussion of our recent research on this topic. I will go through the construction of realistic minimal models for altermagnetism based on symmetry arguments, and reveal the mechanisms stabilizing this phase by examining analytic expressions for the susceptibility. Additionally, I discuss the application of minimal models to relevant altermagnetic material candidates, including RuO2, MnF2, FeSb2, κ-Cl, CrSb and MnTe, and find that it gives rise to a large Berry curvature linear in the spin-orbit coupling. Finally, I present a Landau free energy expansion and analytic expressions for the Landau coefficients from the minimal model, investigating the interplay between weak ferromagnetism and the altermagnetic order parameter at domain walls and in the presence of spin-orbit coupling. This study allows for a simple way to understand the presence of large anomalous Hall effect but vastly different amplitudes of weak ferromagnetism between altermagnetic compounds.