Polaronic Hall mobility in neodymium nickelate films

Abstract

Knowledge of the carrier mobility is essential for identifying and understanding charge transport mechanisms. This is especially relevant in rare-earth perovskite nickelates ReNiO${}_3$, which exhibit an orders-of-magnitude increase in electrical conductivity upon heating. Here, by studying the conductivity and the Hall effect in thin epitaxial films of neodymium nickelate NdNiO${}_3$, we experimentally establish the Hall mobility over a temperature interval of 4–400 K. The Hall mobility is found to be smaller than $1{\mathrm{cm}}^2/\mathrm{Vs}$ at all temperatures, which indicates carrier localization. A temperature analysis of the conductivity, the Hall coefficient, and the Hall mobility reveals the hopping of small polarons in the low-temperature insulator state, the possible transport of large polarons in the high-temperature conducting state, and percolation-type behavior in the transitional region. The evidenced polaronic transport is suggested to be innate in nickelates.