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Temperature dependence of the threshold of pure and impurity-doped blue bronzes has been studied. It is found that for pare blue bronzes the threshold field near 100K has an anomalous peak, but for impurity-doped samples no anomaly is observed in the range of liquid nitrogen temperature, and the value of the threshold field gradu-ally increases with the decrease of temperature. The results show that in the high-quality pure blue bronzes, there may exist an incommensurate to quasi-commensurate transition near 100K. But for the impurity-doped or "dirty" pure samples, such an incommensurate to quasi-commensurate transition near 100K can be extensively re-strained by impurities or defects, which leads to a pure incommensurate CDW in a wide temperature range. 相似文献
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热电势表示为;S(T)=Sg(T)+Sd(T),Sd(T0和Sg(T)分别是扩散热电势和曳引热电热。高温超导体大量的热电势数据呈现随载流子浓度的系统变化,低载流子浓度区和高载流子浓度区的热电势具有相同的函数形式,这说明从欠掺到过掺杂的热电势应由统一的理论描述。 相似文献
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本文对名义组份为Bi1 .8Pb0 .2Sr2 - xLaxCuOy 系列样品的电阻率和热电势特性进行了实验研究.测量表明,Pb 掺杂可以进一步提高超导转变温度Tc ;随着La 含量的增加,Tc 按照典型的抛物线型规律变化;La 掺杂极大地影响超导体正常态的输运特性.我们的分析指出,热电势在正常态所表现出的规律与高温超导机制密切相关,而且电阻率正常态输运特性的变化可用La 掺杂造成CuO6 八面体顶点氧发生位移来解释. 相似文献
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掺Pb的Bi_(1.4)Pb_(0.6)Sr_2Ca_2Cu_3O_y氧化物是一个以110K 超导相为主的高 T_c 超导体,其零电阻 T_c 为107.1K. dc Meissner 效应表明,110K 相占样品体积的8.2%,85K 相占1.6%.不同磁场下的排磁通(Meissher)效应,超导体所占体积上限和下限的比较,不同磁场和测量电流的 R(T)超导转变,表明了样品中存在着丰富的弱连结超导电性.研究了弱连结超导体的 H_(c2)(T).直流磁化和 I_c(B)特性结果表明,大块 Bi_(1.4)Pb_(0.6)Sr_2Ca_2Cu_3O_y,是个弱钉扎Ⅱ类超导体,它的 H_(cl)(77K)=25Oe,且磁化曲线中有两个峰.加热实验表明,当温度升高到355K 时,样品的正常态电阻增加,零电阻超导 T_c 从107.1K 退化到99.5K. 相似文献
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Structural Domain Imaging and Direct Determination of Crystallographic Orientation in Noncentrosymmetric Ca_3Ru_2O_7 Using Polarized Light Reflectance 下载免费PDF全文
The noncentrosymmetricity of a prototypical correlated electron system Ca3Ru2O7 renders extensive interest in the possible polar metallic state,along with multiple other closely competing interactions.However,the structural domain formation in this material often complicates the study of intrinsic material properties.It is crucial to fully characterize the structural domains for unrevealing underlying physics.Here,we report the domain imaging on Ca3Ru<... 相似文献
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对名义组份为Bi_2Sr_(2-x)□_xCuO_y(x=0.1,0.2,0.3,0.4,0.5,0.6,0.7,其中□为空位)的系列样品的微结构进行了研究。电子衍射的研究表明,缺Sr的Bi-2201相的调制波长随着x值的增加而明显减小。Raman散射结果则显示随着调制波长缩短,晶体的结构畸变加剧,晶格无序度增加。利用调制的晶格失配模型讨论了这种由缺Sr所造成的结构畸变行为,并由此指出在Bi系氧化物中非公度调制与晶格的有序度很可能是相关的,调制波长缩短,晶格无序度增加;反之则减小。
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