Electronic-structure evolution through the metal-insulator transition in RNiO3

We performed a photoemission investigation of the electronic structure of P rNiO3 and NdNiO3 through the first order (paramagnetic) metal to (antiferro magnetic) insulator transition. Surprisingly, the data reveal a temperature -dependent loss of spectral weight near the chemical potential, which exten ds well below the coincident metal-insulator (T-MI) and magnetic (T-Neel) t ransition temperatures. This is in contrast with the behavior in SmNiO3 and EuNiO3, where the two transitions are separate. The spectral properties cl early indicate two distinct regimes for RNiO3 with T-MI = T-Neel and T-MI > T-Neel.