A meta-GGA perspective on the altermagnetism of RuO2
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arXiv
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| Natura: | Preprint |
| Pubblicazione: |
2025
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| _version_ | 1866918231920345088 |
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| author | Meinert, Markus |
| author_facet | Meinert, Markus |
| contents | The metallic oxide RuO$_2$ 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 RuO$_2$ 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 r$^2$SCAN-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 LSDA+U, GGA+U, and meta-GGA+U results on RuO$_2$ 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 r$^2$SCAN-L. I demonstrate that altermagnetism is easily formed upon lattice expansion, hole doping, and uniaxial strain on the c-axis. The r$^2$SCAN-L calculations set conservative thresholds for distortions and doping levels for the onset of altermagnetism in a parameter-free framework. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2512_04995 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | A meta-GGA perspective on the altermagnetism of RuO2 Meinert, Markus Materials Science The metallic oxide RuO$_2$ 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 RuO$_2$ 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 r$^2$SCAN-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 LSDA+U, GGA+U, and meta-GGA+U results on RuO$_2$ 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 r$^2$SCAN-L. I demonstrate that altermagnetism is easily formed upon lattice expansion, hole doping, and uniaxial strain on the c-axis. The r$^2$SCAN-L calculations set conservative thresholds for distortions and doping levels for the onset of altermagnetism in a parameter-free framework. |
| title | A meta-GGA perspective on the altermagnetism of RuO2 |
| topic | Materials Science |
| url | https://arxiv.org/abs/2512.04995 |