Structure and electronic properties of the Ln$_{n+1}$Ni$_{n}$O$_{2n+2}$ layered nickelates

Structures of the recently discovered Ln$_{n+1}$Ni$_{n}$O$_{2n+2}$ (Ln = La, Nd) nickelates have infinite NiO$_{2}$ layers, similarly with superconducting cuprates. Moreover, due to unusually low Ni valance determined by their structures, Ni$^{+/2+}$ atoms posses the same 3d$^{9}$/3d$^{8}$ electronic configuration as Cu$^{2+/3+}$ in cuprates. An important question is whether mimicking the electronic and structural features of cuprates would also result in similar physical properties in nickelates? We have prepared several Ln$_{n+1}$Ni$_{n}$O$_{2n+2}$ phases, including the new ones, in a pure form, which make possible detailed characterization of their structures and properties for the first time. In particular, it was found that resistivity of Ln$_{n+1}$Ni$_{n}$O$_{2n+2}$ is decreasing with the increase of n, revealing a tendency to metallization with the change of doping in NiO$_{2}$ layers. Our recent neutron diffraction, resistivity, magnetic and NMR measurements clarifying the nature of the magnetic transition in La$_{4}$Ni$_{3}$O$_{8}$ is also discussed. 1. Poltavets V.V. \textit{Am. Chem. Soc.} \textbf{2006}, $128$, 9050. 2. Poltavets V.V. \textit{Inorg. Chem.} \textbf{2007}, $46$, 10887. 3. Poltavets V.V. Phys. Rev. Lett. \textbf{2009}, submitted.