Key points are not available for this paper at this time.
The magnetic ground state of single crystalline RuO₂ was investigated by the muon spin rotation/relaxation (SR) experiment. The spin precession signal due to the spontaneous internal magnetic field B ₋₎₂, which is expected in the magnetically ordered phase, was not observed in the temperature range 5--400~K. Muon sites were evaluated by first-principles calculations using dilute hydrogen simulating muon as pseudo-hydrogen, and B ₋₎₂ was simulated for the antiferromagnetic (AFM) structures with a Ru magnetic moment | m ₑₔ|0. 05B suggested from diffraction experiments. As a result, the possibility was ruled out that muons are localized at sites where B ₋₎₂ accidentally cancels. Conversely, assuming that the slow relaxation observed in SR spectra was part of the precession signal, the upper limit for the magnitude of | m ₑₔ| was estimated to be 4. 8 (2) 10^-4 ₁, which is significantly less than 0. 05B. These results indicate that the AFM order, as reported, is unlikely to exist in the bulk crystal.
Hiraishi et al. (2024) studied this question.