Electronic transport in nanostructured thin films of perovskite manganite La_0.67Ca_0.33MnO₃: role of grain boundaries

Abstract

We have prepared nanostructured thin films of La_0.67Ca_0.33MnO₃, with an average grain size of around 18 nm, using the chemical solution deposition method. The film has a metal-insulator transition at around T_P=225 K and shows appreciable magnetoresistance (MR) over the entire temperature range of 4 K<T<200 K. The observed MR at fields H>0.5 T is nearly temperature independent over a substantial temperature range up to T_P. The observed MR behaviour, as indicated by a simple phenomenological modelling of MR done as a function of both temperature and magnetic field, is due to the appropriate combination of contributions from the grain boundaries (prominent at low temperatures) and the bulk of the grains (prominent close to T_p).