Anomalous Behavior of the Ni${}^{1+}$ moment and interstitial band in bi-infinite-layered La${}_3$Ni${}_2$O${}_5$F

The discovery of superconductivity in hole-doped Ni${}^{1+}$ systems with “infinite layer” NiO${}_2$ square-lattices analogous to the Cu${}^{2+}$ CaCuO${}_2$ cuprate has renewed conflicting pictures of the Cu${}^{2+}$$-$Ni${}^{1+}$ similarity or distinction. Recent synthesis of formal Ni${}^{1+}$ La${}_3$Ni${}_2$O${}_5$F with two infinite NiO${}_2$ layers per cell provides a novel member of this class. First principles density functional theory studies reveal an interstitial density derived single band $E^{\ast }$ in three layers unrelated to any atom, which provides self-doping to a Ni${}^{1.09+}$ ion.The blocking La(O/F)La provides isolation of the NiO${}_2$ bilayer and an interstitial $E^{\ast }$ density to strictly two-dimensional electronic and magnetic systems. Calculations of magnetic tendencies reveals behavior unlike previous nickelates, including vanishing susceptibility up to a large magnetic field. Two dimensional fluctuations and self-doping away from half-filling can account for the lack of observation of a magnetic transition.