以溶膠-凝膠法製備LaMnO3摻雜Sn之超巨磁阻薄膜

Magnetoresistance Properties of the Perovskite La1-xSnxMnO3(0＜x≦0.15) Films Prepared by Sol-Gel Method

張儷瓊(Li-Chung Chang)

指導教授 ： 王玉瑞

國立臺北科技大學/工程學院/材料及資源工程系所/碩士(2005年)

https://doi.org/10.6841/NTUT.2005.00306

摘要

具超巨磁阻效應之混和價數的Ln1-xAxMnO3鈣鈦礦結構氧化物，以往A多為二價之元素如Ca+2、Sr+2等等，本實驗以四價之Sn作為研究探討之材料。在製程方面目前學術界主要以雷射脈衝沈積法(Pulse laser deposition，PLD)來製作此類材料之磊晶膜，使用之基板大多為昂貴的LaAlO3、SrTiO3、MgO 陶瓷單晶基板。然而PLD限制就是無法鍍大面積高品質薄膜，且價格昂貴，因此在工業界的應用受限。且據前人研究發現多晶薄膜因自旋極化穿隧效應，在比較低的磁場下就有不錯的磁阻表現。故本研究利用溶膠-凝膠法中之Pechini法以金屬硝酸鹽、氯化物作為起始原料，檸檬酸當螯合劑，加入乙二醇與檸檬酸聚酯化反應為溶膠，經膠化後形成三度空間網狀聚合物之凝膠。以旋鍍的方式將膠鍍於(100)矽基板上，備製多晶形態之La0.9Sn0.1MnO3 薄膜。實驗上除了探討製程變數對性質之影響，更希望能提升室溫磁阻率、金屬絕緣性轉換溫度，以及改善溶膠-凝膠薄膜之表面粗糙、裂縫現象，期能增加應用性、實用性，但因為無量測磁阻之儀器，故未能討論其磁阻。
另一部分主要在研究以溶膠-凝膠法製備鈣鈦礦結構之單相塊材。以突破前人未能作出此成分之鈣鈦礦結構之單相塊材。但是雖然作出鈣鈦礦結構之單相塊材但是緻密度甚低。

關鍵字

溶膠-凝膠法 ； Pechini法 ； 旋鍍法 ； 超巨磁阻 ； 鈣鈦礦結構 ； 多晶薄膜

並列摘要

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.

並列關鍵字

Sol-gel method ； Pechini method ； Perovskite ； Polycrystal thin films ； spin coated ； Colossal magnetoresistance (CMR)

參考文獻

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