銦/銀奈米顆粒的鄰近效應與自旋極化之探討; The proximity effect and spin polarization in In/Ag nanocomposites

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题名:	銦/銀奈米顆粒的鄰近效應與自旋極化之探討;The proximity effect and spin polarization in In/Ag nanocomposites
作者:	鄭皓今;Zheng,Hao-Jin
贡献者:	物理學系
关键词:	銦;銀;超導;鄰近效應;自旋極化;奈米顆粒;indium;silver;superconductivity;proximity effect;spin polarization;nanoparticle
日期:	2013-07-02
上传时间:	2013-08-22 11:47:29 (UTC+8)
出版者:	國立中央大學
摘要:	摘要　　此次實驗使用熱蒸鍍法製造銦/銀奈米顆粒，其粒徑大小分別為銦奈米顆粒9 nm、銀奈米顆粒9.6 nm。接著以銦/銀重量百分比為16:84之比例製造樣品，再逐步壓合樣品，縮短顆粒與顆粒的間距，其間距以壓合密度(packing fraction f )表示，藉此觀察其鄰近效應所帶來之影響。　　本次實驗由物理特性量測系統(PPMS)進行量測。在磁性部份，使用Langevin函數加上一反磁項進行磁化強度對於外加磁場的擬合。在改變壓合密度的情況下，高壓合密度其反磁磁化率均低於低壓合密度。但在相同壓合密度的情況下，則是高溫的反磁現象比較明顯。　　超導性質的部份，其交流磁化率隨著溫度上升之改變，使用Scalapino函數擬合。但在高壓合密度的低溫區部份，並無法使用Scalapino函數良好擬合，我們認為此部份有新的超導抗磁分量出現。觀察高壓合密度的χ”(T)也可發現有新的超導貢獻出現，可能是由於鄰近效應在銀奈米顆粒中誘發超導，使得樣品內的古柏電子對數目增多，導致超導抗磁增強。 Abstract 　 We measure the superconductivity and magnetic properties of In/Ag nanocomposites by tuning interparticle separations. The indium and silver nanoparticles were fabricated by thermal evaporation method. The mean diameters, determined from the peak width of the X-ray diffraction patterns, are 9 nm and 9.6 nm for In and Ag, respectively. 　The superconductivity and magnetic properties were measured on PPMS (Physical Property Measurement System). The variation magnetization M with the applied magnetic field can be described by Langevin function plus a Lenz’s diamagnetic term χd.The diamagnetic χd with high packing fraction f is weaker than low packing fraction f. 　The χ’(T) curves can fit to the Scalapino’s equation, giving the superconducting parameters such as Tc, χsc and λ0. The Tc doesn’t change significantly upon increasing the packing fraction f. Howerver, the superconductor diamagnetic screening signals largely increase in the high packing fraction sample. We suggest that there is a new superconductor diamagnetic component emeraging at low temperature in the high packing fraction sample. We propose that the new superconductor component is induced in Ag nanoparticles by In nanoparticles.
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