奈米銦的超導性對奈米鎳引發的鄰近效應之抗衡; The superconductivity of indium nanoparticles contend with the proximity effect induced by nickel nanoparticles

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題名:	奈米銦的超導性對奈米鎳引發的鄰近效應之抗衡;The superconductivity of indium nanoparticles contend with the proximity effect induced by nickel nanoparticles
作者:	陳柏翰;Bo-han Chen
貢獻者:	物理研究所
關鍵詞:	奈米顆粒;鎳;銦;鄰近效應;超導;nickel;indium;proximity;superconducting;nanoparticles
日期:	2011-07-01
上傳時間:	2012-01-05 14:41:12 (UTC+8)
摘要:	本論文改變銦、鎳兩種奈米顆粒混合樣品的質量比例，並透過測量樣品的磁化強度及磁化率來觀察銦、鎳樣品各別的磁性與超導性，以及混合後產生的鄰近效應。實驗用的奈米顆粒是使用熱蒸鍍冷凝法製備，並以共同體積函數法分析，得出樣品顆粒粒徑分別是13.9 nm的銦，及3.1 nm的鎳。　　首先，磁化率隨溫度變化關係的部分，以Scalapino表示式擬合超導相變溫度。可以發現當鐵磁性的鎳質量比例增加，銦的超導相變溫度並不會受到明顯的影響，預期中鐵磁性破壞超導性的現象並未顯現，表示銦的超導溫度能夠抗衡鎳加入之後的效應。另一方面，Scalapino表示式擬合所得的穿透深度隨鎳的比例增加而升高，表示超導體被穿透的部分增加。　　而磁化強度的部分，觀察到不同比例鎳的飽和磁化強度比銦高出3到43倍不等，表示大外加磁場的磁性由鎳主導；而在小外加磁場區，超導相變溫度之下的降場行為，會引發磁化強度忽然急劇下降的現象。此現象被認為是超導抗磁引發的結果，分析後發現此現象來自於鎳成份較低時的反轉磁滯，及鎳成份較高時的超導抗磁性增強。　　We study the proximity effect between the ferromagnetic Ni nanoparticles (NPs) and superconducting In NPs. The In100-XNiX nanocomposites are prepared by mixing two NPs with different mass ratio but constant packing fraction. The NPs are both prepared using thermal evaporation method and the mean diameters of In and Ni NPs were determined by the XRD patterns, where are 13.9 nm and 3.1 nm, respectively. 　　To study the influence of proximity effect on the superconducting parameters, we measured the magnetic AC susceptibility χ’ of the nanocomposites. By fitting χ’(T) to the Scalapino’s expression, the transition temperature TC and the mean penetration depth are obtained. The penetration depth increases with the increasing mass percentage of Ni NPs, but the TC doesn’t decrease but keeps constant at Ni NPs content up to 45%. 　　In the other hand, the DC magnetization M were measured at several selected temperatures. For the In NPs, the paramagnetic M(H) curves are observed above TC, while the hysteresis arose by the geometric barrier are observed below TC. The inverted hysteresis, where the remanent magnetization of the reversal curve from the loop 2 is smaller than the initial value from loop 1, appears in low Ni mass ratio, and the enhancement of the superconducting diamagnetic magnetization are found in In80Ni20, In75Ni25, and In55Ni45.
顯示於類別:	[物理研究所] 博碩士論文

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