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
Grace A. Pan, Qi Song, Dan Ferenc Segedin, Myung‐Chul Jung, Hesham El‐Sherif, Erin E. Fleck, Berit H. Goodge, Spencer Doyle, Denisse Córdova Carrizales, Alpha T. N’Diaye, Padraic Shafer, Hanjong Paik, Lena F. Kourkoutis, Ismail El Baggari, Antía S. Botana, Charles M. Brooks, Julia A. Mundy
Abstract
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 ${\mathrm{Nd}}_{n+1}{\mathrm{Ni}}_{n}{\mathrm{O}}_{3n+1}$ using molecular beam epitaxy. By optimizing the stoichiometry of the parent perovskite ${\mathrm{NdNiO}}_{3}$, we can reproducibly synthesize the $n=1\ensuremath{-}5$ 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 $3{d}^{8}$ to $3{d}^{7}$ as we move across the series from $n=1$ to $\ensuremath{\infty}$. The $n=3\ensuremath{-}5$ compounds exhibit weakly hysteretic metal-to-insulator transitions with transition temperatures that depress with increasing order toward ${\mathrm{NdNiO}}_{3}$ $(n=\ensuremath{\infty})$.