Giant 16O – 18O isotope effect on the metal-insulator transition of RNiO3 perovskites (R = rare earth)

Abstract

The observation of unusually large, positive and rare-earth dependent 16O − 18O isotope shifts in the metal-insulator transition temperature (ΔTMI ≤ + 10.3K_). The results clearly indicate that the mechanism of the transition involves a strong electron-lattice interaction. A simple model based on the existence of Jahn-Teller polarons in a stoichiometric, metallic, charge-transfer system is used to account for the evolution of ΔTMI along the series. © 1998 The American Physical Society.