釔鋇銅氧高溫超導體之製程和磁性研究

Abstract

以直流濺射鍍膜系統,在氧化鎂基板上成長的釔鋇銅氧薄膜,經X-光繞射， R-T，SEM，TEM及AES分析，在基板溫度Ts=680-720C及氣體流量比Ar/ O2=100/12，可擁有c軸方向及臨界溫度達84K的平坦薄膜。其臨界電流密 度在60K時可達10E5A/cm2。在加入適當大小的電流可證明電子遷移對超導 特性有正面的效應。經液相方法可得到一具有特殊晶相排列的釔鋇銅氧塊 材。我們探討其磁性異常，磁通跳躍及FC磁化特性和磁滯迴路的關係。當 外加磁場平行ｃ軸方向，其殘餘磁滯鬆弛特性顯示，傳統Anderson-Kim理 論無法完整解釋因此我們期望集體釘扎模型理論可以解釋它。 A self-designed single target DC sputtering system was used to deposit the YBaCuO(Y-123) thin films. Many methods were used to characterize the YBaCuO thin films, including x-ray diffraction patterns, R-T measurements, SEM, TEM, AES depth profiles, and electromigration studies. Under the conditions of substrate temperature Ts=680-720 C and Ar/O2=100/12, a better c-axis oriented YBaCuO film with Tco=84 K can be got. The film on MgO substrate possesses a critical current density of about 100000 A/cm2 at 60 K. A preferentially-oriented bulk YBaCuO superconductor was prepared by liquid phase method. The anomalies in the magnetization, flux jump effect and the FC magnetization and the hysteresis loop relationship have been discussed. The remanent magnetization relaxation with field parallel to the c-axis shows that the simple conventional flux creep model can not explain the phenomenon and the collective pinning model is expected to explain it.