Oxygen diffusion in La_2/3Ga_1/3MnO₃ and Sr₂FeMoO₆ thin films

Abstract
Thin films of colossal magnetoresistance La_0.67Ca_0.33MnO₃ (LCMO) (d=200+300 nm), highly conductive LaNiO₃ (LNO) (150+200 nm), double perovskite Sr₂FeMoO₆ (SFMO) ( 70 nm) as well as LCMO/LNO bilayers were grown heteroepitaxially by dc magnetron sputtering and pulsed laser deposition on lattice-matched NdGaO₃(100) and SrTiO₃(100) to investigate oxygen diffusion in LCMO, LNO and SFMO. In-situ electrical resistance measurements were performed at (78+1000) K in vacuum (p10^-4 Pa) and oxygen gas (p 10⁵ Pa) by varying temperature of the films linearly with time : T(t)=T₀β t. The activation energy of oxygen ion diffusion, E_D, of 1.3 eV and 1.2 eV have been estimated for the LCMO and LNO films, respectively, by fitting numerical and experimental data. Unusual resistance changes of the Sr₂FeMoO₆ thin films during their annealing in oxygen at T ≥ 500K had showed formation of high resistance regions in the vicinity of grain boundaries.