Quasi-symmetry Constrained Spin Ferromagnetism in Altermagnets

Abstract

Altermagnets break time-reversal symmetry and their spin-orbit coupling (SOC) allow for an anomalous Hall effect (AHE) that depends on the direction of the Néel ordering vector. The AHE and the ferromagnetic spin moment share the same symmetry and hence are usually proportional. However, density functional theory (DFT) calculations find that the AHE exists with negligible ferromagnetic spin moment for some compounds, whereas it reaches sizable values for other altermagnets. By examining realistic minimal models for altermagnetism in which the DFT phenomenology is captured, we uncover a general SOC-enabled quasi-symmetry, the uniaxial spin space-group, that provides a natural explanation for the amplitude of the ferromagnetic spin moment across the vast range of different altermagnetic materials. Additionally, we derive analytic expressions for the magnetic anisotropy energy, providing a simple means to identify the preferred Néel vector orientation for altermagnets.

5 pages, 2 figures, matches journal version

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Cited by in corpus (9)

• Tuning of altermagnetism by strain
• Dominant orbital magnetization in the prototypical altermagnet MnTe
• Relativistic Spin-momentum locking in altermagnets
• Inherent momentum-dependent gap structure of altermagnetic superconductors
• Strain-tunable anomalous Hall effect in hexagonal MnTe
• Staggered Dzyaloshinskii-Moriya and canting angle in centrosymmetric altermagnetic and ferromagnetic phases: influence on the anomalous Hall effect and Weyl points
• Relativistic spin-momentum locking in ferromagnets
• Physical Pictures for Quasisymmetry in Crystals
• Altermagnetism from the viewpoint of chemistry