Microscopic Magnetism of Nickel-Based Infinite-Layer Superconducting Parent Compounds RNiO₂ (R = La, Nd): A μSR Study

Abstract By using muon spin relaxation (μSR) measurements, we perform a comparative study of the microscopic magnetism in the parent compounds of infinite-layer nickelate superconductors RNiO₂ (R = La, Nd). In either compound, the zero-field μSR spectra down to the lowest measured temperature reveal no long-range magnetic order. In LaNiO₂, short-range spin correlations appear below T = 150 K, and spins fully freeze below T ∼ 10 K. NdNiO₂ exhibits a more complex spin dynamics driven by the Nd 4f and Ni 3d electron spin fluctuations. Further, it shows features suggesting the proximity to a spin-glass state occurring below T = 5 K. In both compounds, the spin behavior with temperature is further confirmed by longitudinal-field μSR measurements. These results provide new insight into the magnetism of the parent compounds of the superconducting nickelates, crucial to understanding the microscopic origin of their superconductivity.