Spin-glass state in nickelate superconductors

Magneto-optical measurements in La${}_{0.8}$Sr${}_{0.2}$NiO${}_2$ and Nd${}_{0.825}$Sr${}_{0.175}$NiO${}_2$ reveal an intriguing new facet of infinite-layer nickelate superconductors: the onset of spin-glass behavior at a temperature far exceeding the superconducting critical temperature $T_c$. This discovery sharply contrasts with copper oxide superconductors, where magnetism and superconductivity remain largely exclusive. Moreover, the magnitude and onset temperature of the polar Kerr effect in Nd${}_{0.825}$Sr${}_{0.175}$NiO${}_2$ fabricated on SrTiO${}_3$ and (LaAlO${}_3$)${}_{0.3}$(Sr${}_2$TaAlO${}_6$)${}_{0.7}$ substrates differ dramatically, while $T_c$ does not.