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標題: | 拓樸絕緣體經磁性鄰近效應產生電子結構重組之研究 Electronic Modification in Topological Insulator via Magnetic Proximity Effect |
作者: | 李彥勲 Yen-Hsun Lee |
指導教授: | 林敏聰 |
關鍵字: | 拓撲絕緣體,磁性鄰近效應,TIG垂直磁異向性,X光磁圓偏振二向性,磁性,反常量子霍爾效應, topological insulator,magnetic proximity effect,TIG,PMA,XMCD,magnetism,QAHE, |
出版年 : | 2017 |
學位: | 碩士 |
摘要: | 被磁化的拓撲絕緣體有著由磁性誘發的時間對稱性破壞,使其被視為觀測反常量子霍爾效應的關鍵,雖然磁性鄰近效應是其中一個磁化拓撲絕緣體的方案,但這個方案還是被磁性層的性質所限制著,直到最近TIG被製造出來,其具有垂直磁異向性並且為磁性絕緣體被認為是觀測反常量子霍爾效應最有潛力的磁性物質之一,我們的工作是藉由X光吸收光譜與X光磁圓偏振二向性的元素解析特性以研究拓樸絕緣體與磁性絕緣體TIG的磁異質結構在拓樸絕緣體所造成的磁性鄰近效應與電子結構的重組,有著垂直磁異向性的TIG在低溫時會產生強矯頑力,並且被磁化拓撲絕緣體的X光磁圓偏振二向性的訊號在20K時被觀測到在Te的M4,5吸收峰,希望可以藉由良好的X光技術以獲得對拓樸絕緣體與磁性絕緣體TIG的磁異質結構系統更好的理解以利應用於自旋電子學之中。 The magnetic topological insulator (TI) is regarded as a key to turn on quantum anomalous Hall effect (Q-AHE) as a result of the time-reversal irreversibility driven by the spontaneous magnetization. Although magnetic proximity effect is one of the best methods to magnetize TI, the research is still limited by the property of ferromagnetic layers. Recently, a novel perpendicular anisotropy ferromagnetic insulator: TIG has been manufactured and also considered as the best candidate to induce Q-AHE. This work aims at investigating the magnetic proximity effect concerning the correlation among magnetism and the electronic structure in a topological insulator heterojunctioned with a TIG ferromagnet, which is denoted TI-TIG. By utilizing the combined x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD), that enables an element-specific probe to realize the mechanism of magnetic proximity effect in giving rise to the exchange coupling between the two layers. TIG featured the perpendicular magnetic anisotropy and strong coecivity in low temperature. XMCD-like asymmetry was performed at Te M 4,5 -edges at 20K in TI, and antiferromagnetic coupling between Te and Fe^tet was also performed. Thanks to the excellent capability of x-ray technique, we hope to have a better understanding on this TI-TIG system in relation to its spintronic application. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/20659 |
DOI: | 10.6342/NTU201702261 |
全文授權: | 未授權 |
顯示於系所單位: | 物理學系 |
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