顆粒間交互作用對安德森錫奈米超導與自旋極化的影響; Effects of interparticle interaction on superconductivity and spin-polarization of Anderson Sn nanoparticles

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題名:	顆粒間交互作用對安德森錫奈米超導與自旋極化的影響;Effects of interparticle interaction on superconductivity and spin-polarization of Anderson Sn nanoparticles
作者:	陳志昱;Zhi-Yu Chen
貢獻者:	物理研究所
關鍵詞:	奈米粒子;電子自旋極化;超導;錫;nanoparticle;tin;Sn;superconductivity;spin polarization
日期:	2011-07-13
上傳時間:	2012-01-05 14:41:42 (UTC+8)
摘要:	使用熱蒸鍍冷擬法製備錫奈米顆粒，經X光繞射光譜分析粒徑為4 nm，並使用X光繞射光譜分析樣品成分，錫占35%一氧化錫占65%。再由成分比例估算樣品殼層厚度0.6 nm與核心直徑4 nm。藉由改變聚合密度與加熱來探討顆粒間距變化對奈米顆粒的超導與自旋極化的影響。樣品觀察到自旋極化，並且發現在聚合密度較低時，磁化曲線隨溫度的變化不明顯，聚合密度升高飽和磁化強度隨溫度上升而下降。飽和磁化強度隨顆粒間距有先上升後下降的趨勢，隨著溫度升高此變化趨勢變得不明顯。聚合密度f=2.3到f=76%皆未發現超導相轉變，而交流磁化率在聚合密度低時沒有變化，聚合密度高時略為上升。樣品於加熱溫度100℃時出現超導抗磁現象，隨著加熱溫度升高抗磁增加，加熱溫度180℃的抗磁大小約為100℃的3倍。使用Scalapino公式擬合超導轉變溫度發現有隨加熱溫度略為上升。 The nanoparticle powerder Sn_100725 was fabricated by the thermal evaporation method. The XRD pattern was used to characterize the sample. The mean particle diameter was determined to be 4 nm by X-ray diffraction profiles. The composition of Sn/SnO is analyzed by refining the X-ray diffraction pattern using General Structural Analysis System (GSAS) program. The core diameter is calculated from the composition. Interparticle separation is adjusted by a hydraulic press. The superconducting diamagnetic screening effect was measurement through AC magnetic susceptibility. The temperature dependence of in-phase component can be described by the Scalapino’s expression. Superconductivity was not observed when packing fraction at f=2.3% to f=76%. Then anneal the sample from 100℃ to 180℃. When anneal at 100℃ the superconductivity appeared and as the annealing temperature increase the superconducting diamagnetic screening effect and Superconductor critical temperature increase. The spin polarization effects are observed in M(H) curve which can be described by Langevin function. The saturation magnetization was not depend on temperature obviously When the interparticle separation is far. When interparticle separation was closer, the saturation magnetization changed from increase to decrease and as the temperature increase the saturation magnetization decrease.
顯示於類別:	[物理研究所] 博碩士論文

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