Sodium doped lanthanum manganites thin films: Influence of the oxygen content on the structural parameters

We report the structural characterisation of La1-xNaxMnO$_{3+\delta}$thin films deposited by Rf-magnetron sputtering onto SrTiO3(100) single crystal substrates. In particular, we focussed our attention on a series of samples annealed at different pO2, ranging from 1 to 10-6atm. XRD and microRaman data show an expansion of the perovskite lattice for samples annealed in reducing conditions. This results agree with general manganite gas-solid equilibrium involving the formation of Mn4+as the oxygen content increases. For pO$_{2}\,{<}\,10^{-6}$atm the structure rearranges because of the increasing the oxygen vacancies and the volume of the unit cell shrinks.