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姓名 陳姿蓉(Tzu-jung Chen) 查詢紙本館藏 畢業系所 物理學系 論文名稱 奈米錫顆粒之超導與自旋極化間共存及互競現象
(Coexistence and Competition between Superconductivity and Spin Polarization in Sn Nanoparticles.)相關論文 檔案 [Endnote RIS 格式]
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摘要(中) 採用熱蒸鍍法製備錫奈米顆粒,以Sn_071205表示。透
過AFM與X光繞射鑑定‧徑為7 nm,從X光螢光分析與
X光繞射圖分析,確定Sn_071205樣品成份皆為錫,無
氧化物或者其他元素。
由磁化曲線及變溫磁化率曲線可觀察到Sn_071205樣
品同時具有超導抗磁性及自旋極化效應,兩種效應可
以共存。進一步以壓合的方式改變樣品顆‧間距,在
顆粒間距較大的區域,可觀察到超導抗磁性減弱且自
旋極化增強,判斷兩種效應不單只有共存,彼此之間
還會相互競爭。顆粒間距S=9.5 nm時,庖立順磁磁化
率與飽和磁化強度同時具有極大值。於顆粒間距S=6.9
nm時,樣品產生轉變,庖立順磁磁化率與飽和磁化強
度同時逆勢變小,且於實驗溫度1.8 K以上觀察不到超
導抗磁性,之後繼續壓合超導抗磁性又逐漸增強。
探討超導臨界溫度隨顆粒間距變化趨勢,受到超導能
隙Δ以及平均單電子能階分離能隙δ隨顆粒間距變化
的影響,其關係曲線共可區分為四個區域。此外在低
聚合密度的區間,超導抗磁性的減弱使得穿透深度隨
顆粒間距縮短而逐漸加深,與本實驗室去年的研究大
致上相符合。摘要(英) Sn nanoparticles were fabricated by thermal
evaporation method. Atomic force microscope images
and x-ray diffraction patterns were performed to
examine particle diameter and composition. A pure 7
nm Sn nanoparticle powder was obtained. No trace of
oxidation or other impurity was found.
AC magnetic susceptibility and magnetization
measurements were performed to study the magnetic
properties. Superconductivity and spin polarization
were observed to coexist at low temperatures. To
study the interplay between spin polarization and
superconductivity, the M-H curves at different interparticle separations were measured. Coexistence and
competition between superconductivity and spin
polarization were found for inter-particle separation
that is greater than 6.9 nm. No superconductivity may
be found at an inter-particle separation of 6.9 nm. As
the inter-particle separation was reduced further, the
superconductivity signals recovered.
The inter-particle interactions linked to the critical
temperature can be divided into four regimes. It is the
competition between superconductivity and spin
polarization that govern the behavior.關鍵字(中) ★ 錫
★ 超導
★ 自旋極化關鍵字(英) ★ superconductivity
★ Sn
★ Tin
★ spin polarization論文目次 論文摘要.....................................I
目錄........................................II
圖目與表目..................................IV
第一章 簡介
1-1 塊材錫的基本物理特性.....................1
1-2 奈米錫顆粒的超導與自旋極化...............2
1-3 奈米顆粒的超導相變磁特徵曲線............ 4
1-4 實驗動機.................................6
第二章 實驗儀器與樣品製備分析
2-1 低真空熱蒸鍍冷凝系統.....................8
2-2 粒徑分析................................11
2-3 成份分析................................19
2-4 物理特性量測系統........................23
第三章 超導與自旋極化參數分析討論
3-1 自旋極化................................26
3-2 磁特徵曲線擬合..........................33
3-3 臨界溫度與外加磁場的關係................36
3-4 穿透深度與外加磁場的關係................38
3-5 庖立順磁磁化率與外加磁場的關係..........42
第四章 顆粒間距對超導與自旋極化之影響
4-1 樣品壓合................................45
4-2 磁化曲線擬合............................48
4-3 低溫磁特徵曲線擬合......................58
4-4 顆粒間距對超導參數的影響................64
第五章 結論.................................72
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影響 ,中央大學碩 士論文(2008).指導教授 李文献(Wen-Hsien Li) 審核日期 2008-6-30 推文 plurk
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