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A meta-GGA perspective on the altermagnetism of RuO2

Markus Meinert*

  • New Materials Electronics Group, Department of Electrical Engineering and Information Technology, Technical University of Darmstadt, Merckstr. 25, 64283 Darmstadt, Germany

  • *Contact author: markus.meinert@tu-darmstadt.de
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Phys. Rev. Materials 10, 054411 – Published 15 May, 2026

DOI: https://doi.org/10.1103/gqhb-2h45

Abstract

The metallic oxide RuO2 hosts a fascinating edge case of magnetism: while nonmagnetic in ideal bulk material, density functional theory (DFT) predicts an altermagnetic ground state within the DFT+U method. The magnetic state of strained or doped thin films remains controversial, but evidence for a nontrivial magnetic state is ample. Here, I study the altermagnetic ground state of RuO2 on a higher rung of Jacob's ladder of density functional approximations, the meta-GGA level including the kinetic energy density and the density Laplacian. While the workhorse functional of solid-state physics is a generalized gradient approximation (GGA), the modern r2SCAN-L functional has been established as a general-purpose functional which can replace GGA, while systematically improving solid-state properties without introducing spurious errors like erroneous magnetic ground states. Comparison of local spin-density approximation (LSDA)+U, GGA+U, and meta-GGA+U results on RuO2 shows systematic enhancement of the exchange interaction, leading to a reduction of the onset value of the Hubbard U parameter at different levels of density functional approximation. However, the magnetic ground state, studied at the experimental lattice constants, remains nonmagnetic with r2SCAN-L. I demonstrate that altermagnetism is easily formed upon lattice expansion, hole doping, and uniaxial strain on the c axis. The r2SCAN-L calculations set conservative thresholds for distortions and doping levels for the onset of altermagnetism in a parameter-free framework.

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Phys. Rev. Materials 10, 054411– Published 15 May, 2026
  • Received 5 December 2025
  • Accepted 5 March 2026
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