Effects of annealing temperature and oxygen partial pressure on the magnetoresistivity of c-axis oriented La_(0.9)Sr_(0.1)MnO_(3+δ) thin film

摘要

Using the sol-gel spin-coating method, c-axis oriented La_(0.9)Sr_(0.1)MnO_(3+δ) thin film has been prepared. The excess oxygen δ values and Mn~(4+) proportions in La_(0.9)Sr_(0.1)MnO_(3+δ) thin films with different annealing temperatures and oxygen partial pressures have been determined from the defect model. For La_(0.9)Sr_(0.1)MnO_(3+δ) thin film, the oxygen reduction at 1073 K in 1 Pa O_2 is enough to obtain samples without excess oxygen. The electrical and magnetic measurements reveal that the resistivity peak temperature T_p is almost equal to the ferromagnetic transition temperature T_c. The experimental results indicate that T_c cannot be solely determined by the Mn~(4+) proportion. Probably, Mn and La site (especially Mn site) vacancies play another important role in determining T_c. The excess oxygen δ in those thin films should be taken into account in investigating the magnetotransport behavior.