| Summary: | 碩士 === 國立臺北科技大學 === 材料及資源工程系所 === 93 === In recent years, the rare earth manganite Ln1-xAxMnO3 (Ln=rare earth ion, A=Ca, Sr, Ba, or Pb) with the perovskites strcuture have been received renewed attention due to the colossal magnetoresistance (CMR) effects. However, for single crystals or highly textured films, the effects are limited by temperature and the applied field. Some people found that the negative MR of the polycrystalline samples was dominated by spin-polarized tunneling between grains, and the key feature observed was a large negative MR at very low fields associated with magnetic domain rotation at the grain boundaries. In this study we hope to develop a material with high MR at high temperatures and low fields. Polycrystal La1-xSnxMnO3 (LSnMO) thin films by Pechini method were spin coated on Si (100) substrates. The sol-gel of metal nitrates and chloride dissolved in a water solution containing citric acid, and diethylene glycol was used to produce the colloidal particles (sol) of chelate from polyesterification.
A metal-insulator transition was observed in all films, but two peaks were presented, and showed the difference with the others reported. The metal-insulator transmission takes place at a temperature TP and moves to a hight temperature with the increment of film thickness as well as the tin concentration. A series of LSnMO films synchesied exhibit transition from ferromagnetic to paramagnetic at TC, and the Curie temperature TC also increases with the increasing tin concentration.
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