Synthesis and electronic properties of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Nd</mml:mi><mml:mrow><mml:mi>n</mml:mi><mml:mo>+</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi>Ni</mml:mi><mml:mi>n</mml:mi></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mrow><mml:mn>3</mml:mn><mml:mi>n</mml:mi><mml:mo>+</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math> Ruddlesden-Popper nickelate thin films

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