(Anti-)Altermagnetism from Orbital Ordering in the Ruddlesden-Popper Chromates Sr${}_{n+1}$Cr${}_n$O${}_{3n+1}$

Abstract

Altermagnets are collinear antiferromagnets with spin-split electronic states. We introduce Ruddlesden-Popper chromates Sr${}_{n+1}$Cr${}_n$O${}_{3n+1}$ (including SrCrO${}_3$) as candidate materials in which altermagnetism can emerge from spontaneous orbital ordering rather than crystal symmetry. First-principles calculations reveal a layer-dependent spin splitting: if the spin and orbital orders align in adjacent layers, the system exhibits non-relativistic spin splitting, and thus altermagnetism. In contrast, if either the spin or the orbital order is reversed in adjacent layers, we observe a layerwise uncompensated spin splitting, that is compensated in the adjacent layer, giving rise to the concept of anti-altermagnetism. In the RP series, odd $n$ members support coexistence of altermagnetism and anti-altermagnetism, whereas even $n$ and the perovskite limit are strictly anti-altermagnetic. In both cases, larger $n$ favors metallicity, and in odd $n$ compounds strain can further stabilize altermagnetism.

4 pages, 5 figures + supplementary

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Cited by in corpus (5)

• Superconducting phenomena in systems with unconventional magnets
• Quantum anomalous Hall effect with tunable Chern numbers induced by d-wave sublattice-staggered altermagnetism
• Altermagnetism from the viewpoint of chemistry
• Second-order topological insulator induced by compensated altermagnetism without bulk spin splitting
• Effect of spin-orbit coupling on spin and orbital ordering in Sr${}_{n+1}$Cr${}_n$O${}_{3n+1}$, $n=1,2$