電&#64005;式(p-type)龐磁阻(CMR)材&#63934;La1-xAxMnO3 (A=鹼&#63754;屬元素，0≦x≦1)其獨特的磁阻效應一直是大家感興趣的研究課題，近&#63886;&#63789;許多電子式(n-type)龐磁阻材&#63934;La1-xTxMnO3 (T=四價元素，0≦x≦1)也&#63955;&#63955;續續發表。然而，這些研究並沒有直接的證據(如Hall&#63870;測)支持成功合成之事實。在這篇&#63809;文中，我們選擇最為廣泛研究的LCeMO與LTeMO材&#63934;，重覆其實驗並&#63965;用場發射式掃描式電子顯微鏡(FESEM)及X射線能&#63870;散佈分析儀(EDS)分析微結構，發現這些材&#63934;中並未如其他研究小組所宣稱成功化合LCeMO和LTeMO相，而是分&#63904;成許多雜相。另外，考慮元素間電負&#64001;之關係和摻雜&#63870;對晶格之影響後，我們嘗試經由&#63847;同合成&#63799;徑合成R1-xCexMnO3 (R=Nd, Dy, Ho, Y and Yb) x≦0.3，但全部&#64038;如LCeMO和LTeMO樣品一般分解成&#63849;種&#63847;同的成份。再由另外的角&#64001;(&#63978;子半徑)&#63789;分析MnO6八面體的穩定&#64001;上，發現Mn2+的&#63978;子半徑極大，導致八面體的tolerance factor相對的小(<0.9)而導致結構&#63847;穩。於是，樣品趨向於合成&#63849;種&#63847;同成份的相，而&#63847;反應成&#63972;想中的結構。

Hole-doped colossal magnetoresistance (CMR) materials La1-xAxMnO3(A=alkaline metal，0≦x≦1) has been extensively studied because of its unique magnetoresistance characteristic and potential capability in application. Recently, many suspicious electron-doped CMR materials have been reported. However, none of them were supported by direct data such as Hall measurement. In this thesis, we reinvestigate these results by reproducing LCeMnO and LTeMnO samples with reported process, then by used of field emission scanning electron microscopy (FESEM) and Energy Dispersive Spectrum (EDS) to analysis their possible composition and microstructures. It is found that the previous reports have made the same problems in trusting their indirect measurement results without the direct observation in microstructure level. In our study, both LCeMnO and LTeMnO in either air or Ar sintering process undergo decomposition situation that made them contain various impurity phases. By considering electronegativity between various rare earth ions and the doping rate, we test various compounds R1-xCexMnO3 (R=Nd, Dy, Ho, Y and Yb) with x≦0.3. They all undergo similar situations as that happened in LCeMnO and LTeMnO compounds. By investigation the ionic radius of Mn2+ to the bond length in Mn-O of the MnO6 octahedron, the final possibility of the reason why it is not possible to form n-type CMR material in bulk format is the large ion radius Mn2+ introducing extra small tolerance factor (<0.9) that increases structure instability. As a result of that, forming various phases is much prefer than remains in the structure of mother’s compound.

目錄
第一章 簡介………………………………………………………01
第二章 基本理論…………………………………………………03
2-1 物質磁性介紹……………………………………………03
2-1-1 順磁性(paramagnetism)…………………………03
2-1-2 反磁性(diamagnetism)……………………………04
2-1-3 鐵磁性(ferromagnetism).………………………05
2-1-4 反鐵磁性(antiferromagnetism)…………………06
2-2 磁阻介紹…………………………………………………07
2-2-1 常磁阻(Ordinary MR, OMR)..……………………08
2-2-2 異向磁阻(Anisotropic MR , AMR)………………08
2-2-3 巨磁阻(Giant MR, GMR)………………………08
2-2-4 穿遂磁阻(Tunneling MR, TMR)…………………09
2-2-5 龐磁阻(Colossal MR ; CMR)……………………09
2-3 電子摻雜龐磁阻材料研究回顧………………………… 10
第三章 實驗方法…………………………………………………14
3-1 樣品製作…………………………………………………14
3-2 電性量測…………………………………………………17
3-3 電性量測系統…………………………………………… 17
3-4 X光繞射系統 (X-Ray diffraction system) ………………17
3-5 場發射型掃描式電子顯微鏡(SEM)……………………18
3-5-1 二次電子影像(Secondary Electron Image-SEI) …19
3-5-2 背向散射電子(Backscattered Electrons Image-BEI).19
3-5-3 能量散佈分析儀（Energy Dispersive Spectrum-EDS）19
第四章 數據分析與討論……………………………………21
4-1 La0.8Te0.2MnO3……………………………………………21
4-2 La0.7Ce0.3MnO3……………………………………………25
4-3 R0.7Ce0.3MnO3(R=Nd、Dy、Ho、Y)……………………… 29
4-4 Ho1-xCexMnO3、Yb1-xCexMnO3 (x=0.05、0.1、0.2、0.3)…34
第五章 結論.………………………………………………44
References.………………………………………………45
附錄………………………………………………47

[1] M. Julliere. Phys. Lett. 54A, 225(1975)
[2] R. von Helmolt, J. Wecker, B. Holzapfel, L. Schultz, and K. Samwer
Phys.Rev. Lett. 71, 2331 (1993).
[3] C. Zener, Phys. Rev. 81,440 (1951).
[4] A. J. Millis el al. Phys. Rev. Lett. 74, 5144 (1995)
[5] Charles Kittel. 〝Introduction to Solid state physics〞, 7th ed. WILEY.
[6] G. T. Tan, S. Dai, P. Duan, Y. L. Zhou, H. B. Lu, and Z. H. Chen,J. Appl. Phys. 93, 5480 (2003)
[7] G. Tan, X. Zhang, and Z. Chen, J. Appl. Phys. 95, 6322 (2004).
[8] G. T. Tan, S. Y. Dai, P. Duan, Y. L. Zhou, H. B. Lu, and Z. H.
Chen, Phys. Rev. B 68, 014426 (2003).
[9] C. Mitra, Journal of Applied Physics, 89, 524 (2001)
[10] P. Mandal and S. Das, Phys. Rev. B 56, 15073 (1997)
[11] C. Mitra, Z. Hu, P. Raychaudhuri, S. Wirth, S. I. Csiszar, H. H.
Hsieh, H.-J. Lin, C. T. Chen, and L. H. Tjeng, Phys. Rev. B 67,
092404 (2003).
[12] J-S Kang, Y. J. Kim, B. W. Lee, C. G. Olson, and B. I. Min, J.
Phys.: Condens. Matter 13, 3779 (2001).
[13] G. Tan, P. Duan, G. Yang, S. Dai, B. Cheng, Y. Zhou, H. Lu, and
Z. Chen, J. Phys.: Condens. Matter 16, 1447 (2004).
[14] H. chou, C. B. Wu, S. G. Hsu, and C. Y. Wu, Phys. Rev. B 74, 174405 (2006)
[15] R. D. Shannon, Acta Crystallographica. (1976). A32, Pages 751-767
[16] Goodenough, J. B.; Longo, J. M. In Magnetic and Other Properties in Oxides and Related Compounds; Hellwege, K. H., Hellwege, A. M., Eds.; Springer-Verlag: Berlin, 1970. Landolt-Bo&uml;rnstein, New Series, Group III, Vol. 4a, Chapter 3, p 126.
[17] John Philip and T R N Kutty, J. Phys. Condens. Matter 11 (1999) 8573-8546
[18] Tomoji Kawai, Solid State Communications 129(2004) 785-790