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11.
研究了Cd替代Ca对CaLaBaCu_5O_7体系超导电性的影响.电阻率测量结果表明,T_c随Cd含量x的增加单调下降,同时正常态电阻率随x增加而上升.在x=0-1范围内,体系经历超导-类半导体-绝缘体转变.Hall测量结果表明,CuO_2面内迁移空穴浓度p_(ab)随Cd含量增加而单调下降,这与Tc的变化相对应.样品的热重测量结果表明,氧含量对Ca_(1-2)Cd_5LaBaCu_5O_7,体系的正常态和超导态性质产生很大影响.Cd替代Ca导致Cu-O链上的氧空缺.随着Cd含量的增加,氧含量单调下降.C
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12.
In this paper it is reported that the measurement of the bulk positron lifetime as a function of substitution content x in the temperature range from 70 to 220K was performed in two high-Tc superconducting systems, Y1-xCaxBa2Cu3-xFexO7-δ and Y1-xCaxBa2Cu3O7-δ. It was found that τB of both systems decreases significantly with x and the temperature dependence of τB is very weak in normal state. In lower temperature region (Tc), a dramatic x-dependent temperature variation of τB was observed in the Ca-substituted system: from a decrease of τB with decreasing T to an increase of τB. With increasing x, the temperature dependence of τB remains weak in the Ca- and Fe- substituted systems. Compared with the experimental data of positron lifetime in other substituted systems and the calculation of the positron density distribution, the authors suggest that positron bulk lifetime spectra behaviour can be interpreted by the physical model based on the transfer of electron density between the CuO2 planes and Cu-O chains. Therefore, the study of positron lifetime spectra provides a useful means to detect the local charge density and to study the correlation between the electronic structure and the high-Tc superconductivity. 相似文献
13.
基于中子散射实验结果,应用键价计算方法研究了Y_(1-x)Pr_xBa_2Cu_3O_(7-δ)(x=0,0.2,0.4,0.6)体系中离子的价键特性。对Cu(1),Cu(2)及Y(Pr)的键价和计算结果表明,Cu(2)的键价和与超导临界温度(T_c)之间存在着强烈的关朕。在氧含量基本保持不变的情况下,随Pr含量的增加,体系中电荷分布发生改变,Cu(1),Cu(2)的键价和下降,Y(Pr)的键价和上升,CuO_2面内的空穴部分地被局域于Pr-o键上。Pr对超导电性的淬灭,主要应归结为Pr对CuO_2面内空穴的局域化作用。 相似文献
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