Topochemical\nSynthesis and Electronic Structure of\nHigh-Crystallinity Infinite-Layer Nickelates on an Orthorhombic Substrate

Superconductivity\nin infinite-layer nickelates has stirred\nmuch\nresearch interest, to which questions regarding the nature of superconductivity\nremain elusive. A critical leap forward to address these intricate\nquestions is through the growth of high-crystallinity infinite-layer\nnickelates, including the “parent” phase. Here, we report\nthe synthesis of a high-quality thin-film nickelate, NdNiO<sub>2</sub>. This is achieved through the growth of a perovskite precursor phase\n(NdNiO<sub>3</sub>) of superior crystallinity on the NdGaO<sub>3</sub> substrate by off-axis RF magnetron sputtering and a low-temperature\ntopochemical reduction using NaH. We observe a nonlinear Hall effect\nat low temperatures in this “non-doped” phase. We further\nstudy the electronic properties using advanced X-ray scattering and\nfirst-principles calculations. We observe spectroscopic indications\nof the enhanced two-dimensionality and a reduced hybridization of\nNd 5<i>d</i> and Ni 3<i>d</i> orbitals. These\nfindings unlock new pathways for preparing high-quality infinite-layer\nnickelates and provide new insights into the intrinsic features of\nthese compounds.