Temperature-dependent electronic structure of Nd1−xSmxNiO3 Original Research Article

RNiO3 (R: rare earth) is one of the typical bandwidth-control metal–insulator transition systems. Its metal–insulator transition temperature (TMI) is the same as the antiferromagnetic transition temperature (TN) for R=Pr and Nd, while TMI is higher than TN for R=Sm and Eu. The boundary between the two types of phase transitions is located between NdNiO3 and SmNiO3. We have measured photoemission spectra of Nd1−xSmxNiO3 at various temperatures above and below TMI. The spectra show quite different temperature dependences between x≤0.4 and x≥0.6. For x≤0.4, the spectral intensity near the Fermi level (EF) is temperature-dependent even well below TMI, while for x≥0.6 it shows a significant temperature dependence only near TMI. Also, the spectra near EF above TMI show a pseudo-gap like behavior for x≥0.6. From these results, we conclude that the metallic phase has different natures between x≤0.4 and x≥0.6.