摘要
为阐明磁性离子在不同替代位置对YBCO体系超导电性的影响机制 ,利用正电子湮没及相关实验手段结合数值模拟 ,系统研究了Fe和Ni掺杂的YBa2 Cu3O7-δ体系 .结果表明 ,Fe和Ni离子在替代过程中均以离子团簇的形式进入晶格 .当离子进入CuO2 面时 ,由于团簇改变了周围的电子结构 ,造成电子的局域化 ,并直接影响了电子对的配对和输运 ,因而强烈抑制了体系的超导电性 .而当掺杂离子进入Cu_O链区时 ,它们同样通过团簇的形式改变周围的电子结构 ,并抑制空穴载流子的产生及其向CuO2 面区域的有效转移 ,造成载流子的局域化 ,弱化了载流子库的功能 ,然而由于它们仅间接影响了超导电子对的配对和输运 ,因此对超导电性的抑制较弱 .实验结果同时显示 。
To make clear the physical mechanism of substitution by the magnetic ions Fe an d Ni in different sites in YBCO systems, the positro n annihilation technology (PAT) and simulated calculations are utilized to systemically investigate the compounds YBa 2 Cu 3-x (Fe,Ni) x O 7-δ (x=0 0—0 5). The results obtained show that the dopin g ions Fe and Ni form different kinds of ion cl usters and enter the crystal lattice. When occupying Cu(2) sites in CuO 2 p lanes, the ions gather into double square and/or other clusters, which results i n a strong electronic localization and would directly affect the pairing and t ransportation of carriers, so the superconductivity is suppressed dramatically. While ions substitution for Cu(1) through gathering hexamer and/or other cluste rs, this induces the localization of holes and weakens the function of carrier r eservoir; thus carriers cannot easily transfer to CuO 2 planes. However, in this case, the pairing and transportation of carriers are not affected directly, thu s the superconductivity will be suppressed weakly. On the other hand, the presen t results indicate the suppression of superconductivity has no direct correla tion with the magnetism of Fe and Ni ions itself.
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2004年第4期1223-1231,共9页
Acta Physica Sinica
基金
国家自然科学基金 (批准号 :1 0 2 74 0 4 9)
上海市教育委员会科技发展基金(批准号 :0 1A 1 6
0 2AK4 2 )
上海市教育委员会重点学科建设项目资助的课题~~
