Altermagnetism in orthorhombic $Pnma$ structure through group theory and DFT calculations

Abstract

Antiferromagnetism, initially considered interesting but useless, recently emerged as one of the most promising magnetic phases for technology. Recently, a low symmetry antiferromagnetic phase, known as altermagnetic phase, have been discovered, where no time reversal ($\mathcal{T}$) symmetry is observed in spite of a vanishing net magnetization, leading to non-degenerate bands from the opposite magnetic sublattices. In this work, we consider two representatives of orthorhombic $Pnma$ space group, namely, BiFeO${}_3$ and CaMnO${}_3$ and find altermagnetic lowest energy phase in both from our density functional theory calculations. We find a substantial spin-splitting in both systems along a high-symmetry path in the Brillouin zone without considering the spin-orbit interaction (SOI). Detailed features of the band dispersion obtained from our calculation confirm the lifting of sublattice spin degeneracy only in the $k_y$-$k_z$ plane while preserving the spin degeneracy in the other planes of the Brillouin zone. We provide a comprehensive symmetry analysis based on the magnetic space group (MSG) to explain our DFT findings and an insightful symmetry-allowed model Hamiltonian, which qualitatively agrees with our results. Additionally, we extend our symmetry analysis to encompass two other potential MSGs within the $Pnma$ space group that may host the spin-splitting phenomenon without considering SOI and the likely form of their Hamiltonian. These detailed studies pave the way for a deeper understanding of the spin-splitting phenomena within the $Pnma$ space group, offering insights into the intricate interplay between symmetry and electronic as well as magnetic properties.

12 pages, 8 figures

References in corpus (9)

• The ferroelectric-paraelectric phase transition in BiFeO3: crystal structure of the orthorhombic beta-phase
• Observation of Giant Band Splitting in Altermagnetic MnTe
• Crystal Thermal Transport in Altermagnetic RuO2
• Absence of altermagnetic spin splitting character in rutile oxide RuO${}_2$
• Topological transition from nodal to nodeless Zeeman splitting in altermagnets
• Anisotropy of the anomalous Hall effect in the altermagnet candidate Mn${}_5$Si${}_3$ films
• Coexistence of Anomalous Hall Effect and Weak Net Magnetization in Collinear Antiferromagnet MnTe
• Interplay of altermagnetism and weak ferromagnetism in two-dimensional RuF${}_4$
• Interplay between altermagnetism and nonsymmorphic symmetries generating large anomalous Hall conductivity by semi-Dirac points induced anticrossings

Cited by in corpus (3)

• Superconducting phenomena in systems with unconventional magnets
• Tunneling Magnetoresistance Effect in Altermagnets
• Designing Non-Relativistic Spin Splitting in Oxide Perovskites