English  |  正體中文  |  简体中文  |  Items with full text/Total items : 57355/90942 (63%)
Visitors : 13092345      Online Users : 225
RC Version 7.0 © Powered By DSPACE, MIT. Enhanced by NTU Library & TKU Library IR team.
Scope Tips:
  • please add "double quotation mark" for query phrases to get precise results
  • please goto advance search for comprehansive author search
  • Adv. Search
    HomeLoginUploadHelpAboutAdminister Goto mobile version
    Please use this identifier to cite or link to this item: http://tkuir.lib.tku.edu.tw:8080/dspace/handle/987654321/32561

    Title: 電子掺雜對層狀不相稱的鈷氧化物Ca3-xYxCo4O9 物理性質之影響
    Other Titles: Effect of electron doping on physical properties of misfit-layered cobaltite Ca3-xYxCo4O9
    Authors: 潘俊傑;Pan, Jiun-jie
    Contributors: 淡江大學物理學系碩士班
    林大欽;Ling, Dah-chin
    Keywords: 磁電傳輸;強關聯費米液體;自旋密度波;鐵磁的關聯性;陶鐵磁性;spin-density-wave;ferromagneticcorrelation;ferrimagnetism
    Date: 2006
    Issue Date: 2010-01-11 02:21:25 (UTC+8)
    Abstract: 我們詳細地研究了層狀不相稱的鈷氧化物Ca3-xYxCo4O9 (CYCO) 的物理性質。CYCO系統的電阻率隨著Y摻雜量的增加單調地遞增,意味著系統中的電洞濃度隨著Y3+對Ca2+部份取代的增加而遞減。在 T ~ Tmin 附近,電阻率 有一個極小值。當T > Tmin, 電阻率 呈現金屬的行為,同時 遵循T2一直到 T*,對於 x = 0, T* ~ 170 K;x = 0.2, T* ~ 230 K,這明確地告訴我們CYCO在金屬態時是一個強關聯的費米液體。相對地,當T < Tmin, 電阻率 呈現半導體的行為;值得注意的是Tmin隨著Y摻雜量的增加從62 K單調地遞增至120 K。更有趣的是與自旋密度波能隙相關的量dln(R)/d(1/T)在相對應的溫度出現一平台,同時dln(R)/d(1/T)的數值亦隨著Y摻雜量的增加而增加,這說明Tmin 與自旋密度波起始溫度成正比,並且Y摻雜量的增加伴隨著自旋密度波起始溫度的升高。另外,dln(R)/d(1/T)在與陶鐵磁性相關的溫度20 K附近開始隨溫度的降低逐漸遞減,意味著陶鐵磁性的出現對於自旋密度波的能隙有抑制的作用,這個現象在磁場下的dln(R)/d(1/T)對溫度關係圖中很清楚地表現出來。從磁傳輸性質隨Y摻雜量變化的關係來看,我們發現Y摻雜所引發的化學壓力與鈷價數的變化對於[Ca2CoO3] 與 [CoO2] 子系統之間的耦合有深遠的影響,進而導致系統中自旋密度波與陶鐵磁性的消長。
    Physical properties of misfit-layered cobaltite Ca3-xYxCo4O9 (CYCO) with polycrystalline samples have been extensively investigated. Electrical resistivity of the Y-substituted sample monotonically increases with increasing Y content, which could be attributed to the decrease of the hole concentration by substitution of trivalent Y3+ for divalent Ca2+. The resistivity exhibits a broad minimum around T = Tmin. At T > Tmin, follows T2 dependence up to T* ~ 170 K for x = 0 and 230 K for x = 0.2 samples, indicating that CYCO is a strongly correlated Fermi liquid in metal state. Whereas T < Tmin, exhibits insulating-like behavior, ranging from 62 K with x = 0 up to 120 K with x = 0.2. The dln(R)/d(1/T), related to the energy gap of SDW, reveals a plateaus and increases with increasing Y content. It suggests that Tmin scales with the onset temperature of SDW and SDW is enhanced by the Y doping. Furthermore, the dln(R)/d(1/T) gradually decreases below a temperature T**, increasing with increasing field for x , at which ferrimagnetism sets in. The variation of interlayer coupling between the [Ca2CoO3] and [CoO2] subsystems caused by substitution-induced chemical pressure as well as valence state change of cobalt has profound influence on the correlated evolution of SDW and ferrimagnetism.
    Appears in Collections:[Graduate Institute & Department of Physics] Thesis

    Files in This Item:

    File SizeFormat

    All items in 機構典藏 are protected by copyright, with all rights reserved.

    DSpace Software Copyright © 2002-2004  MIT &  Hewlett-Packard  /   Enhanced by   NTU Library & TKU Library IR teams. Copyright ©   - Feedback