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

Abstract

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 $E^*$ 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 $E^*$ 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.