Improvement in the long-term stability of parameters of encapsulated magnetic field sensors based on LaSrMnO thin films

The effectiveness of different approaches used for improvement of stability of colossal magnetoresistance-B-scalar magnetic field sensors made from polycrystalline manganite La0.83Sr0.17MnO3 thin films were considered. We show that the ageing process of sensors can be accelerated by annealing the films in Ar atmosphere at 75-125 °C and covering them by hot melt adhesive (polyethylene). Ageing kinetics of electrical resistance and magnetoresistance (MR) were investigated as well as the influence of hot melt adhesive. Despite of increased resistance only small changes of the MR and the temperature coefficient of resistance were observed. The obtained results are explained by the oxygen release, displacement or redistribution which takes place most probably in grain boundaries of polycrystalline manganites. Based on the obtained results optimal conditions for the stabilization of encapsulated sensors parameters were found resulting in the resistance drift less than 1.5% per year.