Study On The Preparation And Magnetic Properties Of Ni-doped PbPdO₂ Films

In this dissertation,Ni-doped PbPdO₂ nanograin films were synthesized by the sol-gel spin-coating method.The influence of the calcination temperature,the Ni-doping level and the film thickness on the phase composition,the morphology,the ion valence state and the magnetic properties of the Ni-doped PbPdO₂ films were studied in detail.The underlying mechanism for the origin of the ferromagnetism of Ni-doped PbPdO₂ film was analyzed.The main research work and the conclusion are listed as follows:?1?The microstructure and magnetic properties of Ni-doped PbPdO₂ films calcined at different temperatures were studied.The films calcined at 550,600 and 650 ? had a single-phase structure.Both the amount of Pb vacancy and the film's grain size increased monotonically with the calcination temperature increasing.As for the magnetic properties,the high-temperature ferromagnetism persisting up to 380 K was obtained in three single-phase Ni-doped PbPdO₂ films.And the ferromagnetic coupling in the film calcined at 650 ? was stronger than those of the other two films.Bound magnetic polaron model based on the Pb vacancies,the doped Ni ions and the Pb ions with a valence higher than 2+ were used to explain the ferromagnetic origin of these Ni-doped PbPdO₂ nanograin films.?2?The influence of the Ni-doping level on the microstructure and magnetic properties of Ni-doped PbPdO₂ film were investigated.The films with the Ni-doping level ranging from 0 to 21 at.% were found to have a nanograin structure.The amount of Pb vacancy within the film increased with the Ni-doping level increasing.Within all undoped and Ni-doped PbPdO₂ nanograin films in this experiment,the ferromagnetisms which can be maintained to the temperature higher than room temperature were observed.As to the underlying mechanism of the ferromagnetism,it was believed that Pb vacancy acts as the defect and the doped Ni ions and/or the Pb ions with a valence higher than 2+ provides the magnetic moments in the Ni-doped PbPdO₂ nanograin film.These three ones form the bound magnetic polaron.The ferromagnetic coupling between different polarons was regared as the origin of ferromagetism within the Ni-doped PbPdO₂ nanograin films.?3?The dependence of the microstructure and the magnetism of Ni-doped PbPdO₂ films on the film thicknesses were analyzed.It can be found that the films with a thickness ranging from 85 to 350 nm possessed nanograin structures and large amount of Pb vacancies.The ferromagnetisms which can be retained to above the roomtemperature were found in the Ni-doped PbPdO₂ nanograin films with different thicknesses.The ferromagnetic coupling between the bound magnetic polarons based on the Pb vacancy,the doped Ni ions and the Pb ions with a valence higher than 2+ were used to explain the origin of the ferromagnetism in these Ni-doped PbPdO₂ nanograin films.