Synchrotron Spectroscopy of Epitaxial Rare Earth Nickelates

The rare-earth nickelates display a broad range of phenomena, including functional behavior such as antiferromagnetism and superconductivity. The ability to synthesize heterogeneous epitaxial thin film structures out of nickelates enables one to control and modify these functional properties via the creation of atomically abrupt interfaces. Advanced synchrotron characterization can then be used to measure the resulting electronic and magnetic properties of these atomically engineered systems. For example, the antiferromagnetic order parameter of nickelate superlattices can be imaged using resonant soft x-ray diffraction, and information about the dynamics can be accessed by x-ray photon correlation spectroscopy (XPCS) measurements using coherent soft x-rays. In this talk, we focus on synchrotron characterization of the square-planar nickelates, which are a novel class of superconductors. We use in situ aluminum reduction of the perovskite nickelates to achieve superconducting Nd1-xEuxNiO2 (NENO) thin films grown by molecular beam epitaxy (MBE). Atomic structure is characterized using crystal truncation rod (CTR) analysis, and electronic structure is characterized using diffraction-based X-ray absorption near edge structure (dXANES). We also report on the superconducting transport properties of NENO films.