臺灣博碩士論文加值系統

在1966年，美國科學家C.C.Chao就發現CsCl結構的LaAg合金是超導體(Tc=0.9K) [18] [19]。在2009年，LaAg合金只是多參雜了一個磁性元素Mn，Tc馬上升到5K附近[20]。因為在BCS理論中磁性對超導的影響是非常嚴重的問題，BCS理論對磁性元素會造成Tc的上升，不能做出合理的解釋，所以我們很好奇磁性離子在超導扮演的角色，為了釐清磁性離子對超導的影響，我們摻雜磁性離子(特別是稀土元素)到LaAg合金。
我們以電弧氬焊，製作了摻雜稀土元素的La0.9RE0.1Ag0.9Mn0.1樣品(RE=Gd、Dy、Ho、Er元素)， 其中Ho0.1La0.9Ag0.9Mn0.1、Er0.1La0.9Ag0.9Mn0.1樣品在高溫區時，磁化率隨著溫度上升而下降，明顯符合居禮定律；在低溫區，有超導向轉變。

The intermetallic compound LaAg with CsCl-type structure was founded to be superconductor (Tc=0.9K) by American scientist C.C.Chao in 1966 [18] [19]. Furthermore it was found that the superconducting transition temperature Tc was enhanced to 5k with minor doping of magnetic element Mn in the LaAg system In 2009. For a long time, the magnetic elements play a peculiar character in the development of the superconductivity history, in particular to the BCS theory. It couldn’t make a reasonable explanation how magnetic element enhances Tc. So we were curious about the role of the magnetic ions appeared in this superconducting system. In this research, we doped rare earth magnetic ions to the intermetallic compound LaAg in order to clarify the interplay between the magnetism and the superconductivity,.

We used arc argon welding to produce specimens of La0.9RE0.1Ag0.9Mn0.1 (RE=Gd、Dy、Ho、Er elements). The magnetic susceptibility decreased with temperature in the high temperature region were detected in the Ho0.1La0.9Ag0.9Mn0.1 and Er0.1La0.9Ag0.9Mn0.1 compounds. Obviously, the behavior is consistent with the Curie-Weiss law. Surprisingly, a superconducting transition was observed around 5.5 K in both systems at low temperature region.

摘要 i
Abstract ii
目錄 iii
圖目錄 v
第一章簡介 1
1-1超導歷史 1
1-2.BCS理論 3
1-3.超導體特性 4
1-4.磁性物質 6
1-5.單晶材料與多晶材料的差異 12
第二章儀器介紹 13
2-1. X光粉末繞射儀(XRD) 13
2-2. MPMS(Magnetic Property Measurement System) 15
2-3. 電子天平秤重儀 19
第三章實驗步驟與方法 21
3-1.實驗流程圖 21
3-2. 樣品材料特性 22
3-3.樣品製備 26
3-4.樣品量測 28
第四章實驗結果分析 29
4-1.材料的臨界溫度Tc 29
4-2.磁化率的分析 33
4-3.磁滯曲線的分析 38
4-4.超導與磁性並存的證明 45
4-5.超導結構與XRD 49
結論 50
參考文獻 51

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