銦/鎳奈米顆粒複合系統的自旋反屏蔽效應;Spin anti-screening effect in superconducting In/Ni nanocomposites.

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/54252

Title:	銦/鎳奈米顆粒複合系統的自旋反屏蔽效應;Spin anti-screening effect in superconducting In/Ni nanocomposites.
Authors:	陳柏璁;Chen,Bo-Tsung
Contributors:	物理研究所
Keywords:	鄰近效應;自旋屏蔽效應;超導奈米顆粒;superconducting nanoparticles;spin screening effect;proximity effect
Date:	2012-07-20
Issue Date:	2012-09-11 18:40:49 (UTC+8)
Publisher:	國立中央大學
Abstract:	本實驗以銦、鎳奈米顆粒組成的複合系統作為零維超導鄰近效應實驗樣品。奈米顆粒的製作採用熱蒸鍍法，並以X光繞射實驗判定奈米顆粒的結構與粒徑。由共同體積函數擬合X光繞射譜圖後，可得知銦、鎳奈米顆粒的平均直徑分別為16nm與5 nm。實驗分為兩個部分:第一部分改變銦、鎳奈米顆粒的質量百分比，鎳質量百分比介於0 %至10 %共五種樣品。第二部分改變銦、鎳奈米顆粒的壓合密度，壓合密度由4 %壓至74 %共13個樣品。由這兩部分實驗來觀察鄰近效應隨銦、鎳奈米顆粒質量比與銦、鎳奈米顆粒距離的變化。實驗時樣品以液氦降溫至超導臨界溫度附近，測量樣品在低溫時的交流磁化率與直流磁化強度。在超導參數部分，我們由交流磁化率隨溫度變化圖χ-T圖可得到樣品的超導抗磁磁化率大小，並由擬合得到超導臨界溫度TC與磁穿透深度。在改變銦、鎳奈米顆粒質量百分比實驗，超導參數並無顯著的改變。在改變銦、鎳奈米顆粒壓合密度實驗，超導參數隨著壓合密度不同有明顯的漲落行為。在磁性部分，我們在壓合密度高於25%時觀察到磁化強度隨著溫度低於超導臨界溫度TC而明顯上升的現象。此現象可能來自於自旋反屏蔽效應(spin antiscreening)，隨著壓合密度上升自旋反屏蔽的效果也更明顯。Indium and nickel nanoparticles were fabricated by thermal evaporation method. The mean diameters of indium and nickel nanoparticles determined by XRD are 16 nm and 5 nm. The indium/nickel nanocomposites consist of indium and nickel nanoparticles. To investigate the proximity effect of indium and nickel nanoparticles, we changed the mass ration of the two components and the interparticle separation by cold press.The ac magnetic susceptibility measurement shows that critical temperature and superconducting diamagnetic increase with the packing fraction. The critical temperature of tightly packed nanocomposite is 3.66 K, which is 8% higher than loosely packed nanocomposite.The magnetization measurement shows that the magnetization of tightly packed nanocomposites increased with lowering temperature below the critical temperature TC. It is suggested that magnetic moment induced in the superconductor caused by spin antiscreening effect. Generally speaking, the spin antiscreening effect enhanced with decreasing the separation of nanoparticles.
Appears in Collections:	[Graduate Institute of Physics] Electronic Thesis & Dissertation

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