Synthesis and electronic properties of Ndn+1NinO3n+1 Ruddlesden-Popper nickelate thin films

The rare-earth nickelates possess a diverse set of collective phenomena including metal-to-insulator transitions, magnetic phase transitions, and upon chemical reduction, superconductivity. Here, we demonstrate epitaxial stabilization of layered nickelates in the Ruddlesden-Popper form Ndn+1NinO3+1 using molecular beam epitaxy. By optimizing the stoichiometry of the parent perovskite NdNiO3, we can reproducibly synthesize the n = 1 - 5 member compounds. X-ray absorption spectroscopy at the O K and Ni L edges indicate systematic changes in both the nickel-oxygen hybridization level and nominal nickel filling from 3d(8) to 3d(7) as we move across the series from n = 1 to infinity. The n = 3 - 5 compounds exhibit weakly hysteretic metal-to-insulator transitions with transition temperatures that depress with increasing order toward NdNiO3 (n = infinity).

Automated summary

Epitaxial stabilization of rare-earth nickelates in the Ruddlesden-Popper form Ndn+1NinO3+1 has been demonstrated using molecular beam epitaxy. The stoichiometry of the parent perovskite NdNiO3 can be optimized to reproducibly synthesize the n = 1 - 5 member compounds. X-ray absorption spectroscopy reveals systematic changes in nickel-oxygen hybridization and nominal nickel filling across the series from n = 1 to infinity.