Bi2-xMnxSe3的核磁共振研究

Abstract

本篇論文是以核磁共振(NMR)的方式來研究同屬於拓樸絕緣體系列中摻雜過渡金屬的Bi2-xMnxSe3，樣品的製備方式與Mn摻雜濃度x分別為：Bridgeman Method製備的Bi2-xMnxSe3，濃度x=0及x=0.05；化學氣相傳輸法製備的Bi2-xMnxSe3，濃度x=0.01、0.03、0.05和0.15。我們主要量測元素為Bi2-xMnxSe3中的209Bi核磁共振頻譜訊號。 所有摻雜Mn的樣品209Bi核磁共振頻譜的頻率偏移均為負值，且頻率偏移量與Mn摻雜濃度x成正比，其原因為摻Mn後能帶結構改變使得自旋轉移與g-factor軌道交互作用對頻率偏移的影響。Bi2-xMnxSe3中Bi原子的最鄰近出現Mn的位置隨摻雜濃度x增加而提升，其反應在209Bi的核磁共振頻譜上會出現一個與摻雜Mn濃度有關的峰值，量測此峰值的 可發現Bi2-xMnxSe3在20K附近會出現磁性的short-range correlation。

This thesis is used nuclear magnetic resonance to study the topological insulator of Bi2-xMnxSe3. Bi2-xMnxSe3 grown by Bridgeman Method with x=0,x=0.05 and Chemical Vapor Transport with x=0.01,0.03,0.05,0.15,respectively. We measured the 209Bi NMR signals of Bi2-xMnxSe3. According to the emerging peak position of 209Bi specturm, we infer that the sign of the frequency shift caused by the Mn ions is negative. The negative frequency shift in a semiconductor strongly depends on the band structures that determine the orbital involved in the spin transfer and the sign of the g-factor in the contact interaction. We found the emerging peak of Bi2-xMnxSe3 at around 20 K implies a magnetic short-range correlation.