μSR study of the magnetism of bulk infinite-layer nickelate LaNiO₂

Infinite-layer superconducting nickelates RE_1-x(Sr,Ca)_xNiO₂ (RE: rare earth) has attracted great interest in the viewpoint of several similarities to the high-T_c cuprates, such as the 3d⁹ electronic configuration and the infinite-layer crystal structure. While an antiferromagnetic long-range order is formed in the parent compounds of cuprates without carrier doping, the magnetism of the parent nickelates has not been clarified yet. This is partly because the superconductivity does not appear in bulk samples but only in thin films, limiting experimental techniques to investigate [1,2]. To clarify the magnetic ground state of the parent nickelates, we synthesized the bulk infinite-layer nickelate LaNiO₂ polycrystals using molten hydroxide and CaH₂ [3] and performed muon-spin-relaxation measurements.

It was found that the initial asymmetry decreased rapidly at ~ 30 K, suggesting the occurrence of a magnetic transition. At the base temperature of 6.5 K, while the magnetic volume fraction reached ~ 100%, slowly fluctuating spins remained. Moreover, muon-spin precession was not observed. These results suggest the formation of a short-range magnetic order in the parent LaNiO₂.



[1] J. Fowlie et al., Nat. Phys. 18, 1043 (2022).

[2] H. Lu et al., Science 373, 213 (2021).

[3] T. Takamatsu et al., Jpn. J. Appl. Phys. 49, 093101 (2010).