Multi-step accelerated ageing of magnetic field sensors based on nanostructured La-Sr-Mn-O thin films

Abstract

We present results of investigation of influence of accelerated ageing on electrical resistivity and magnetoresistance of nanostructured La-Sr-Mn-O films used for magnetic field sensors. The 400 nm thick manganite films were grown by MOCVD technique. To investigate the effectiveness of accelerated ageing, the two methods were tested: 1) annealing the samples at 100 C temperature in Ar atmosphere when film surface was uncoated, and 2) annealing of the samples coated prior to treatment by polymer. The samples were studied without and in pulsed magnetic fields up to 20 T. To describe the underlying processes, the kinetics of resistivity change during accelerated ageing was analysed using stretched exponent relaxation function. It was found that the change of resistivity of coated samples saturates after significantly shorter accelerated ageing time than uncoated samples. Both ageing methods resulted in minor influence (<1%) on magnetoresistance of the films in magnetic fields up to 20 T.