| Summary: | 碩士 === 義守大學 === 材料科學與工程研究所 === 85 ===
The La0.67 (Ca/Ba/Sr)0.33 MnO3-xand La0.60 (Y/Nd)0.07 (Ca/Ba/Sr)0.33 MnO3-x plates were prepared by mixing of raw material powders and organic solvent at a ratio of 3:2, shaping by a doctor blade method and sintering at 1400℃ for 4hr. The density of plates is raised, as the time of mixing/grounding of calcined powder as well as the sintering temperature increase. At room temperature, the La-Ca-Mn-O is paramagnetic, and exhibits a MR ratio of only -2.9%. The MR ratio is increased as temperature decreases, and reaches a maximum MR ratio of -41.1% at 230K. A Y3+ doping enhances the MR in La-Ca-Mn-O plate; which display a MR ratio as high as -93% at 85K. Both La-Ba-Mn-O and La-Sr-Mn-O plates show the ferromagnetic behavior at room temperature. The MR ratio of La-Ba-Mn-O film drops as temperature decreased. On the other side, the La-Sr-Mn-O shows an increasing tendency of MR ratio, as temperature is lowered. The exact reason of this temperature dependency of MR ratio is not quite understood at this moment.
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