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研究生：	陳勁甫 Chen, Chin-fu
論文名稱：	59Co核磁共振研究熱處理對CoTiSb物理特性的影響 59Co NMR study of the heat treatment effects on the physical properties of CoTiSb
指導教授：	呂欽山 Lue, C. S.
學位類別：	碩士 Master
系所名稱：	理學院 - 物理學系 Department of Physics
論文出版年：	2009
畢業學年度：	97
語文別：	中文
論文頁數：	48
中文關鍵詞：	核磁共振
外文關鍵詞：	NMR, half-Heusler
相關次數：	點閱：68 下載：3
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為了瞭解熱效應對CoTiSb的微觀費米面的態密度(DOS)的影響，我們利用59Co NMR光譜去研究了未熱處理(as-prepared sample)及熱處理後(annealed sample)的樣品。經由量測這兩個樣品的77K到300K自旋—晶格鬆弛時間(T1)，發現它們具有半金屬的特性，在高溫時具有半導體的激發現象，在低溫時則呈現金屬的特性。低溫時的Korringa constant (1/T1T)和費米面上部分的Co 3d 電子態密度DOS Nd(EF)以及軌道順磁貢獻有關。此次研究的結果清楚的顯示熱處理後樣品具有較低的Nd(EF)，此結果造成低溫時具有較高的電阻率，這個結果與其他實驗一致。

With the aim of providing microscopic evidence for the heat treatment driven the reduction of the Fermi-level density of states (DOS) in the Half-Heusler compound CoTiSb, we performed a comparative study of the as-prepared and annealed samples using 59Co NMR spectroscopy. For both materials, the temperature-dependent spin-lattice relaxation rate (1/T1) exhibit semi-metallic characteristics, with an activated response at high temperatures and metallic behavior at low temperatures. We associated the low-temperature Korringa constant (1/T1T) with the partial Co 3d Fermi-level DOS Nd(EF). Results clearly indicate that the annealed CoTiSb possesses a lower Nd(EF), being consistent with other experimental results.

簡介  .....................................................................................................8

第一章 實驗儀器..................................................................................10
1 Arc樣品製備...................................................................................10
2 核磁共振儀.....................................................................................11

第二章 實驗原理..................................................................................14
1 Arc運作原理  ...............................................................................14
2 NMR理論........................................................................................15
2.1 Zeeman effect........................................................................15
2.2 共振吸收..............................................................................16
2.3 運動方程式..........................................................................17
2.4 訊號處理..............................................................................18
2.5 spin-echo................................................................................19
2.6 T1測量...................................................................................20
2.7 Knight-shift奈特位移...........................................................22
2.8 spin-lattice relaxation time.....................................................25

第三章 實驗方法..................................................................................27
1 樣品製作.........................................................................................27
2 CoTiSb 59Co NMR訊號變溫測量..................................................27
3 X-Ray................................................................................................30

第四章 分析討論..................................................................................32
1 X-ray................................................................................................32
2 線型………………………..........................................................34
3 Knight-shift奈特位移......................................................................38
4 Korringa constant (1/T1T)..............................................................41

第五章 結論..........................................................................................45

參考文獻................................................................................................46
                                    

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校內：立即公開
校外：2009-06-22公開

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