Abstract
The complex phase diagrams of strongly correlated oxides arise from the coupling
between physical and electronic structure. This can lead to a renormalization of
the phase boundaries when considering thin films rather than bulk crystals due to
reduced dimensionality and epitaxial strain. The well-established bulk RNiO3 phase
diagram shows a systematic dependence between the metal-insulator transition and
the perovskite A-site rare-earth ion, R. Here, we explore the equivalent phase diagram
for nickelate thin films under compressive epitaxial strain. We determine the metalinsulator
phase diagram for the solid solution of Nd1-yLayNiO3 thin films within
the range 0 ≤ y ≤ 1. We find qualitative similarity between the films and their
bulk analogs, but with an overall renormalization in the metal-insulator transition
to lower temperature. A combination of x-ray diffraction measurements and soft
x-ray absorption spectroscopy indicates that the renormalization is due to increased
Ni–O bond hybridization for coherently strained thin films.
