  Grain boundaries in Sr-doped LaMnO3 thin films have been shown to strongly
influence the electronic and oxygen mass transport properties, being able to
profoundly modify the nature of the material. The unique behaviour of the grain
boundaries can be correlated with substantial modifications of the cation
concentration at the interfaces, which can be tuned by changing the overall
cationic ratio in the films. In this work, we study the electronic properties
of La0.8Sr0.2Mn1-yO3 thin films with variable Mn content. The influence of the
cationic composition on the grain boundary and grain bulk electronic properties
is elucidated by studying the manganese valence state evolution using
spectroscopy techniques and by confronting the electronic properties of
epitaxial and polycrystalline films. Substantial differences in the electronic
conduction mechanism are found in the presence of grain boundaries and
depending on the manganese content. Moreover, the unique defect chemistry of
the nanomaterial is elucidated by measuring the electrical resistance of the
thin films as a function of oxygen partial pressure, disclosing the importance
of the cationic local non-stoichiometry on the thin films behavior.
