Fragility of the magnetic order in the prototypical altermagnet RuO₂

Abstract

Altermagnetism is a topic that has lately been gaining attention and the RuO₂ compound is among one of the most studied altermagnetic candidates. However, the survey of available literature on RuO₂ properties suggests that there is no consensus about the magnetism of this material. By performing density functional theory (DFT) calculations, we show that the electronic properties of stoichiometric RuO₂ are described in terms of a Hubbard U, within DFT+U, smaller than the value required to have magnetism. We further argue that Ru vacancies can actually aid the formation of a magnetic state in RuO₂. This in turn suggests that a characterization of the amount of Ru vacancies in experimental samples might help the resolution of the controversy between the different experimental results.