Ageing effects on electrical resistivity and magnetoresistance of nanostructured manganite films

Abstract

The long-term stability of electrical resistance and magnetoresistance in nanostructured La1-xSrxMnO3 (x = 0.17) manganite thin films grown on lucalox (Al2O3  + MgO) substrate by the MOCVD method was investigated. It was found that the storage of up to 3 months of the free surfaces of these films in normal atmosphere (air) conditions increases their resistivity by almost two times, while the annealing of the films in an Ar atmosphere at 450 °C decreases their resistivity only by 15%. It was concluded that the final increase of resistivity is determined by a long-term relaxation of the grain boundaries in the nanostructured films. The magnetoresistance of the films does not change significantly, which produces an advantage for magnetic field sensor applications. The passive protective coating of the free surfaces of the films stabilizes their electrical and magnetic properties. The results were analysed using various electron scattering mechanisms when the films were in a ferromagnetic state, and the Mott’s variable range hopping model when they were in a paramagnetic insulating state.