In/In2O3奈米顆粒之超導與自旋極化效應探討

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題名:	In/In2O3奈米顆粒之超導與自旋極化效應探討
作者:	林佳穎;Lin,Chia-ying
貢獻者:	物理學系
關鍵詞:	奈米顆粒;超導;磁性
日期:	2013-06-24
上傳時間:	2013-07-10 11:59:58 (UTC+8)
出版者:	國立中央大學
摘要:	本論文藉由改變銦奈米顆粒的氧化程度來探討銦奈米顆粒經過氧化後的超導性與磁性。本實驗利用熱蒸鍍法製備12.5 nm的銦顆粒，再利用加熱氧化法使銦奈米顆粒氧化，並且使用X光繞射譜圖來分析樣品成份及粒徑大小，再利用GSAS分析出氧化的程度。為了探討銦奈米顆粒的超導性，進行了一系列的磁化率量測，得到磁化率隨溫度變化的數據，藉由Scalapino表示式擬合判定超導參數，觀察到超導臨界溫度隨著氧化程度的增加並無顯著的改變。由磁化強度隨外加磁場的變化量測，觀察到自旋極化現象，並使用朗之萬(Langevin function)來描述磁化強度隨磁場變化的行為，擬合的結果為飽和磁化強度隨著溫度的升高而降低，此現象用自旋波熱激發效應來解釋；磁矩隨溫度的升高而增強，此現象用熱磁激發來解釋。接下來利用得到的飽和磁化強度與GSAS擬合得到的銦與氧化銦質量比來推算出銦與氧化銦的單位磁化強度大小，觀察到氧化銦的單位磁化強度大小受熱激發效應比銦來的顯著。 In nanoparticles are fabricated by employing thermal evaporation method and subsequently oxidized in air at a temperature under various oxidation times. XRD is utilized to determine the mean particle diameter (12.5 nm) of the In nanoparticles as grown. The composition of In/In2O3 is analyzed by refining the X-ray diffraction pattern using General Structural Analysis System (GSAS) program. In our study,the superconducting diamagnetic screening effect was measured through AC magnetic susceptibility (? χ?^'=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 (Tc) in the sample after oxidation. The spin polarization effects are seen in M(H) curve which can be described by Langevin function,after fitting,we can get magnetic moment and saturated magnetization.The magnetic moment can be explained by thermal-induced effect.The saturated magnetization can be described by spin-wave excitation model. After that,using GSAS to obtain In and In2O3 mass ratio,and saturated magnetization from Langevin function,we can figure out In and In2O3 magnetization.We found that the thermal-induced effect of In2O3 is more remarkable than In.
顯示於類別:	[物理研究所] 博碩士論文

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