錫奈米微粒的超導參數與自旋極化

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题名:	錫奈米微粒的超導參數與自旋極化
作者:	何鈞考;Jiun-Kao Ho
贡献者:	物理研究所
关键词:	自旋極化;超導;錫;superconducting;Sn;spin polarization
日期:	2006-06-16
上传时间:	2009-09-22 10:58:31 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	論文摘要利用熱蒸鍍法製作錫奈米微粒，藉由調控腔體內的氬氣壓力和加熱電流的大小，製作出不同粒徑的奈米微粒。將各樣品做交流磁化率實驗，利用London公式和Scalapino公式進行擬合。由擬合結果發現，London公式在臨界溫度附近的磁化率擬合曲線較差，而Scalapino公式對於臨界溫度附近的漲落行為有較好的描述。此外，當錫奈米微粒變小，穿透深度也隨之變小。經由擬合得之臨界溫度和臨界磁場隨粒徑減小而變大，在粒徑14nm附近，其臨界溫度和臨界磁場最大，之後隨著粒徑減小而變小。此外由擬合得到各樣品的耦合強度值，發現各樣品的耦合強度隨粒徑的變化趨勢，和臨界溫度與臨界磁場隨粒徑的變化趨勢是一樣的，在粒徑14nm附近，其超導耦合強度最強。 Abstract Tin nanoparticles were fabricated by the thermal evaporation method. A series of eight Tin nanoparticles having different particle diameters was obtained by controlling the Argon pressure and the heating current employed during evoaporation. The temperature dependence of the magnetic susceptibility may be described by using London equation or Scalapino equation. We found that London equation is inadequate in describing the diamagnetic responses in the critical regime where critical fluctuation is evident. The fluctuation behavior exhibited in the regime may be described very well by the Scalapino equation. The penetration depth was found to decrease with reducing particle diameter. The critical magnetic field Hc and the critical temperature Tc were found to be significantly affected by the particle diameter. Variation profiles with peak structures were found in the size dependences of the Hc, Tc, and coupling strength plots. The critical magnetic field and the critical temperature reach the maximum value for 14nm particle .
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