Stabilizing altermagnetism in FeSb₂ via strain

Magnetic materials are traditionally sorted into two types - ferromagnets and antiferromagnets. Recently, a third new type of magnetic order has been proposed: altermagnetism. Altermagnetism is characterized by a spin-split band structure, which is typical of ferromagnets, and no net magnetization, which is typical of antiferromagnets. Previous calculations with FeSb₂ found the ground state to have antiferromagnetic order, but also showed the existence of an altermagnetic phase slightly higher in energy. This suggests that slight changes to the material could stabilize the altermagnetic phase. In this work, we use density functional theory calculations to explore the effect of mechanical strain on magnetism in FeSb₂. We find that under tensile strain, the altermagnetic phase becomes favored. While lattice expansion has only a weak effect on the electronic density of states in the altermagnetic phase, it has a significant effect in the antiferromagnetic phase, causing the Fermi level to shift away from a pseudogap. Without the stabilizing effect of the pseudogap, the antiferromagnetic phase becomes less energetically favorable than the altermagnetic phase.