Ruddlesden-Popper and perovskite phases as a material platform for altermagnetism

TL;DR

This paper demonstrates that Ruddlesden-Popper and perovskite phases are promising platforms for altermagnetism, revealing new candidate materials with diverse electronic properties and complex spin textures, expanding the understanding and classification of altermagnetic systems.

Contribution

The study identifies Ruddlesden-Popper and perovskite phases as universal hosts for altermagnetism and introduces a refined classification scheme based on first-principles calculations.

Findings

Altermagnetism observed in nickel-based systems like La$_2$NiO$_4$

Discovery of candidate materials including La$_3$Ni$_3$O$_7$ and BiFeO$_3$

Spin splittings up to 250 meV and complex spin-momentum textures

Abstract

The subclass of collinear antiferromagnets where spin Kramers degeneracy is broken -- resulting in ferromagnetic-like properties -- offers exciting new opportunities in magnetism and hence motivates the reasoned expansion of the material base for these so-called altermagnets. Here, we show that Ruddlesden-Popper and perovskite phases are generic hosts for altermagnetic behavior. Using first-principles calculations, we demonstrate altermagnetism in prototypical nickel-based systems such as La$_2$NiO$_4$ and identify additional candidates, including the superconducting La$_3$Ni$_3$O$_7$ and the multiferroic BiFeO$_3$. These materials span insulating, semiconducting, and metallic conduction types, with computed nonrelativistic spin splittings reaching up to 250~meV. Our analysis also reveals the presence of accidental nodes and distinct topologies in the spin-momentum texture at the Brillouin-zone boundary, suggesting a refined classification for altermagnetic materials beyond the $d$-wave or higher even-parity wave classes. In addition, we address formal inconsistencies in the traditional classification of magnetically ordered systems, proposing resolutions grounded in the altermagnetic framework, and point out the potential for altermagnetic behavior in systems beyond collinear antiferromagnets with perfectly compensated magnetization, broadening the scope for future exploration.