跳到主要內容

臺灣博碩士論文加值系統

(3.239.4.127) 您好!臺灣時間:2022/08/16 02:55
字體大小: 字級放大   字級縮小   預設字形  
回查詢結果 :::

詳目顯示

: 
twitterline
研究生:張家源
研究生(外文):Chia-Yuan Chang
論文名稱:強關聯鈣鈦礦結構鑭銪鈷氧化合物系統中自旋態轉變之研究
論文名稱(外文):Variation of spin-state transition in strongly correlated La1-xEuxCoO3 pervoskites
指導教授:古煥球
指導教授(外文):Huan-Chiu Ku
學位類別:碩士
校院名稱:國立清華大學
系所名稱:物理學系
學門:自然科學學門
學類:物理學類
論文種類:學術論文
論文出版年:2002
畢業學年度:90
語文別:英文
論文頁數:50
中文關鍵詞:吸收光譜鑭鈷氧同步輻射自旋態轉變
外文關鍵詞:XANESLaCoO3k-edgespin state transitionCo
相關次數:
  • 被引用被引用:0
  • 點閱點閱:154
  • 評分評分:
  • 下載下載:25
  • 收藏至我的研究室書目清單書目收藏:0
La1-xEuxCoO3 (0 £ x £ 1) 的結構,磁性,還有鈷的K層鄰近邊緣的X光吸收光譜 (XANES) 都被報告。因為之前的報導指出RCoO3 的磁性資料都會被稀土元素R3+的訊號所擋住,所以選擇La1-xEuxCoO3 (0 £ x £ 1)系統來作為這次研究的題目,因為Eu3+的基態總角動量為零 (J = 0)。
從低自旋態到中自旋態的自旋態轉變溫度Ts,在x = 0 (LaCoO3)的時候是105 K,在 x = 0.25時是140 K,在x = 0.5時是200 K,然後我們推測當x = 1(EuCoO3)時,Ts將會到達290 K。
在室溫XANES實驗中一個微小的前邊緣特徵被觀察到,它是一個由1s到3d的偶極躍遷,是一個稍微被允許的躍遷,透過Co4p態與Co鄰近原子的3d態之間的混成。中間態LaCoO3在室溫的近邊緣吸收光譜可以被計算由三個峰值圖形所組成並且有能量上的分裂,第二個峰與第一個峰的能量差是2個電子伏特,第三個峰與第二個峰的能量差是1.5個電子伏特。由於鈷熱激發的中間態是d6 (t2g5eg1) 與 d7 L (t2g6eg1 or t2g5eg2)的混合,t2g能態是幾乎填滿的,所以這三個峰應該是分別對應到t2g的自旋向下,eg的自旋向上以及eg的自旋向下。

Structural, magnetic and Co K-edge X-ray absorption near-edge spectra (XANES) studies for the stoichiometric La1-xEuxCoO3 system (0 £ x £ 1) are reported. Because the reported RCoO3 magnetic data are confused by magnetic rare earth R3+ signal, in order to identify the spin-state transition, La1-xEuxCoO3 (0 £ x £ 1) system is chosen as the best candidate with nonmagnetic Eu3+ ground state (total angular momentum J = 0).
The spin-state transition temperature Ts from low-spin (LS) state to intermediate-spin (IS) state increases from ~105 K for x = 0 (LaCoO3), to ~140 K for x = 0.25, ~200 K for x = 0.5 and extrapolated to ~290 K for x = 1 (EuCoO3).
The small pre-edge feature observed in room temperature XANES is from 1s-3d dipole transition, which is weakly allowed through the hybridization of Co 4p states with 3d states of neighboring Co atoms. For LaCoO3 in IS state, pre-edge can be fitted using three peaks with energy separation DE(P2 - P1) = 2.0 eV and DE(P3 - P2) = 1.5 eV. Since the thermally excited IS state is a mixture of d6 (t2g5eg1) and d7 L (t2g6eg1 or t2g5eg2), with almost filled t2g majority spin states, the three peaks P1, P2, P3 are probably corresponding to unfilled t2g minority, eg majority and eg minority states, respectively.

Abstract (Chinese)
Abstract (English)
Contents
List of Figures and Tables
Acknowledgments (Chinese/English)
Chapter 1 Introduction
1.1 Historical Review of the LaCoO3
Chapter 2 Experimental Details
2.1 Sample Preparation
2.2 Power X-ray Diffraction Measurement
2.3 X-ray Absorption Near Edge Spectra (XANES) Measurement
2.4 Magnetization and Magnetic Susceptibility Measurement
Chapter 3 Results and Discussion
3.1 Structural analysis of La1-xEuxCoO3
3.2 X-ray Absorption Near Edge Spectra analysis (XANES)
3.3 Magnetic properties
Chapter 4 Conclusion
References
Appendix

[1] W. C. Koehler and E. O. Wollan, J. Phys. Chem. Solids 2, 100 (1957).
[2] J. B. Goodenough, J. Phys. Chem. Solids 6, 287 (1958).
[3] M. Abbate, J. C. Fuggle, A. Fujimori, L. H. Tjeng, C. T. Chen, R. Potze, G. A.Sawatzky, H. Eisaki, and S. Uchida, Phys. Rev. B 47, 16214 (1993), and references cited therein.
[4] M. A. Senaris-Rodriguez and J. B. Goodenough, J. Solid State Chem. 116, 224 (1995), and references cited therein.
[5] M. A. Korotin, S. Yu. Ezhov, I. V. Solovyev, V. I. Anisimov, D. I. Khomskii, and G. A. Sawatzky, Phys. Rev. B 54, 5309 (1996).
[6] E. Iguchi, K. Ueda, and W. H. Jung, Phys. Rev. B 54, 17431 (1996).
[7] T. Saitoh, T. Mizokawa, A. Fujimori, M. Abbate, Y. Takeda, and M. Takano, Phys. Rev. B 55, 4257 (1997).
[8] S. Yamaguchi, Y.Okimoto, and Y. Tokura, Phys. Rev. B 55, R8666 (1997).
[9] Z. Y. Wu, M. Benfatto, M. Pedio, R. Cimino, S. Mobilio, S. R. Barman, K. Maiti, and D. D. Sarma, Phys. Rev. B 56, 2228 (1997).
[10] K. Asai, A. Yoneda, O. Yokokura, J. M. Tranquada, G. Shirane, and K. Kohn, J. Phys. Soc. Jpn. 67, 290 (1998).
[11] P. Ravindran, P. A. Korzhavyi, H. Fjellvag, and A. Kjekshus, Phys. Rev. B 60, 16423 (1999).
[12] P. Porta, S. de Rossi, M. Faticanti, G. Minelli, I. Pettiti, L. Lisi, and M. Turco, J. Solid State Chem. 146, 291 (1999).
[13] M. Itoh, M. Mori, S. Yamaguchi, and Y. Tokura, Physica B 259-261, 902 (1999)
[14] M. Itoh, J. Hashimoto, S. Yamaguchi, and Y. Tokura, Physica B 281-282, 510 (2000).
[15] L. Sudheendra, Md. M. Seikh, A. R. Raju, and C. Narayana, Chem. Phys. Lett. 340, 275 (2001).
[16] O. Toulemonde, N. N’Guyen, F. Studer, and A. Traverse, J. Solid State Chem. 158, 208 (2001).
[17] J. Androulakis, N. katsarakis, and J. Giapintzakis, Phys. Rev. B 64, 174401 (2001).
[18] X. Liu and C. T. Prewitt, J. Phys. Chem. Solids, 52, 441 (1991).
[19] Y. Y. Kim, D. H. Lee, T. Y. Kwon, and S. H. Park, J. Solid State Chem. 112, 376 (1994).
[20] PCPDFWIN database, JCPDS-International Centre for Diffraction Data (1997).
[21] RIQAS program, Materials Data Inc., Livermore CA, USA (1996).
[22] C. T. Chen, B. N. Lin, Y. Y. Hsu, J. D. Liao, W. H. Cheng, H. C. Ku, J. F. Lee, L. Y. Jang, and T. K. Liu, Phys. Rev. B, submitted (2002).
[23] I. S. Elfimov, V. I. Anisimov, and G. A. Sawatzky, Phys. Rev. Lett. 82, 4264 (1999).
[24] F. Bridges, C. H. Booth, G. H. Kwei, J. J. Neumeier, G. A. Sawatzky, Phys. Rev. B 61, 9237 (2000).

QRCODE
 
 
 
 
 
                                                                                                                                                                                                                                                                                                                                                                                                               
第一頁 上一頁 下一頁 最後一頁 top