Accelerated ageing effects in nanostructured La0.83Sr0.17MnO3 films

Abstract

The kinetics of resistivity and magnetoresistance change was studied during ageing of thin nanostructured La0.83Sr0.17MnO3 manganite films grown on lucalox (99.9% Al2O3+0.01% MgO) substrate by PIMOCVD method. It was obtained that accelerated ageing of the films in Ar atmosphere at temperatures of 100–200 °C as well as long-term ageing during two years at room temperature leads to the significant increase of film resistivity, but has a negligible influence on the magnetoresistance of the film in magnetic fields higher than 1 T. It was found that the accelerated ageing decreases demagnetization field of thin films and, as a result, the magnetoresistance anisotropy is decreased at low field region. The obtained results are analyzed using typical for topologicallydisordered systems model of hierarchically limited relaxation dynamics described by stretched exponent. The analysis of resistivity vs. temperature dependence in paramagnetic state by using Mott's variable range hopping model showed that localization length of charge carriers decreases during annealing or long-term ageing processes. The possible reasons of observed changes are explained by oxygen diffusion and its depletion in the grain boundaries of the films. The possibility to accelerate ageing process of nanostructured manganite films and to achieve higher stability of magneto-resistive sensors based on these films is discussed.