Study the effect of colossal magnetoresistance property of LaMnO3 compounds system by chemical doping

• Main Authors: Liou jyun hong, 劉俊宏
• Other Authors: Lei Chien Ming
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/46970546629639123178

碩士 === 中國文化大學 === 材料科學與奈米科技研究所 === 94 === In this thesis, we study the colossal magnetoresistance property of (La0.85Zr0.15)MnO3 system by using no-magnetic moment Ga3+ ions substitution for Mn ions and its associates with the changes of structure and magnetic property in these compounds. The electron-doped manganites samples are prepared by the solid-state reaction method. Comparing to X-ray data and magnetoresistance measurement results, it can find that if the diffraction pick (110) is stronger then pick (104) which will associate with magnetic phase change. Otherwise, if the diffraction pick (110) is weaker then pick (104) which don’t associate with magnetic phase change. Based on the “Rietveld profile-fitting method”, the all samples are the same symmetric space group ( ). The magnetoresistance (MR) are decreasing with the external field increasing. The temperature of the maximum value of MR is rising with the external field increasing. But the rising rate of 5% Ga doping sample is lower than the undoping sample due to that the no magnetic-moment Ga3+ ions were weaken the magnetic interaction between the Mn3+ ions. The modulus of MR ratio is increasing with the external field increasing and those maximum values are between 220K and 250K that are same with the magnetic phase transition regions. The modulus of MR ratios of the undoping samples are increasing with temperature decreasing and these are almost above 40% under 5 Tesla external fields. The modulus of MR ratio of the 5% Ga doping sample is decreasing with temperature decreasing and it is almost below 40% with 5 Tesla external fields. The modulus of MR ratio is decreasing with the Ga3+ ions increasing, it is from that the Ga ions reduced magnetic interaction between the Mn ions The Curie temperature of the Zr4+ Electron-doped La0.85Zr0.15MnO3 and La0.85Zr0.15(Mn0.95Ga0.05)O3 samples are 240K and 223K, respectively. The magnetic moment of the sample with Ga doping is saturated at lower temperature than the un-doping sample, which is due to the Ga ions’ diluted effect.