Evolution of magnetism in Ruddlesden-Popper bilayer nickelate revealed by muon spin relaxation

Here we report the positive muon spin relaxation study on Pr-doped La${}_{1.9}$Pr${}_{1.1}$Ni${}_2$O${}_{6.97}$ and oxygen-deficient La${}_3$Ni${}_2$O${}_{6.63}$ polycrystalline under ambient pressure. Zero-field ${\mu }^{+}$SR experiments reveal the existence of bulk long-range magnetic order in La${}_{1.9}$Pr${}_{1.1}$Ni${}_2$O${}_{6.97}$ with $T_N=161\mathrm{K}$, while La${}_3$Ni${}_2$O${}_{6.63}$ exhibits a short-range magnetic ground state with $T_N=30\mathrm{K}$. The magnetic transition width of La${}_{1.9}$Pr${}_{1.1}$Ni${}_2$O${}_{6.97}$ revealed by weak-transverse-field ${\mu }^{+}$SR is narrower compared to La${}_3$Ni${}_2$O${}_{6.92}$. Our ${\mu }^{+}$SR experiment results provide a comprehensive view on the correlation between magnetism and structure perfection in Ruddlesden-Popper bilayer nickelates under ambient pressure.