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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/54259

    Title: 錫/鎳奈米顆粒複合系統之超導逆磁鄰近效應;Inverse magnetic proximity effect in superconducting Sn/Ni nanopomposites
    Authors: 陳彥呈;Chen,Yen-Cheng
    Contributors: 物理研究所
    Keywords: 奈米;鄰近效應;反轉磁滯;超導;磁性;superconducting;magnetic;nanoparticle;proximity effect;inverse hysteresis
    Date: 2012-07-23
    Issue Date: 2012-09-11 18:40:58 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 本論文討論錫和鎳奈米顆粒複合系統的超導與磁性現象。將具有磁性的鎳奈米顆粒和超導錫奈米顆粒均勻混和,分別藉由改變樣品鎳含量與顆粒間距離來探討超導與磁性之間的鄰近效應。本研究使用熱蒸鍍冷凝法製備奈米顆粒,使用X光粉末繞射譜圖來判定樣品成分與粒徑。錫與鎳奈米顆粒的平均粒徑分別為10 nm和5 nm。  超導體除了會表現出零電阻特性外,亦可表現在抗磁訊號上。我們進行了一系列磁化率(χ')的測量來探討奈米顆粒複合樣品的超導性質,在考慮臨界溫度(TC)附近的熱擾動效應,使用磁化率(χ')隨溫度變化關係的Scalapino表示式擬合樣品的超導參數。發現在鎳含量低時(<7.5%),超導錫對鎳的磁場有很好的抗衡,臨界溫度(TC)改變不大;在鎳含量為7.5%~12.5%時,超導臨界溫度(TC)反而隨鎳含量升高而有明顯上升趨勢,呈現出超導的逆磁鄰近效應。在錫-鎳複合系統的磁性上,發現了反轉磁滯(inverted hysteresis)的現象,使得系統的殘餘磁化強度值(remanence magnetization)為負值,並且定性分析此現象會在特定條件下出現,這個現象的形成機制尚待釐清,排除了幾個可能的機制後,推測可能是鎳奈米顆粒並非單一粒徑分布所導致。In this thesis, we discuss the superconducting proximity effect in Sn/Ni nanocomposites which is the mixture of Sn and Ni nanoparticles with different mass ratios and packing fractions.The nanoparticles are fabricated by thermal vapor deposition method and are characterized by X-ray diffraction patterns. The average diameters of Sn/Ni are 10/5 nm with FWHM 8.1/4.4 nm. In our study, the superconducting diamagnetic screening effect was measured through AC magnetic susceptibility (χ_ac=χ’ +iχ’’). The temperature dependence of in-phase component χ’(T) can be described by the Scalapino’s expression, which allows extracting the superconducting transition temperature.There is an unconventional enhancement of critical temperature (TC) in the regime of 7.5%~15% of the Ni mass composition. It is observed that an abnormal magnetic behaviors which is so-called inverted hysteresis loops or negative remanence magnetization in the Sn/Ni nanocomposites. The qualitatively analysis was done and a model was given to describe the phenomenon.
    Appears in Collections:[物理研究所] 博碩士論文

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