The decades-long quest for materials that mimic key properties of high-T_c superconducting cuprates has recently culminated in the discovery of superconductivity in Sr-doped infinite-layer (IL) nickelates [1]. However, first spectroscopic studies of the electronic structure [2] and orbital character [3] revealed several differences between cuprates and IL nickelates. Moreover, early experiments on polycrystalline powders of undoped IL nickelates reported a lack of long-range antiferromagnetic order, which is a hallmark of undoped cuprates. To shed new light on the magnetic correlations in IL nickelates, we have measured the dc and ac magnetic susceptibility of LaNiO_2+δ powder, which was obtained from topotactically reduced LaNiO₃. We find that gradual reduction towards the stoichiometric LaNiO₂ phase leads to a strong enhancement of the susceptibility with emerging signatures of spin glass-like dynamics. The glassy behavior is partly reminiscent of the spin glass phase of lightly-doped cuprates and can arise from disorder, impurities, or possibly an intrinsic origin.

[1] D. Li et al., Nature 572, 624 (2019).
[2] M. Hepting et al., Nat. Mater. 19, 381 (2020).
[3] M. Rossi et al., arXiv:2011.00595v1 (2020).