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INTERNAL FRICTION AND ULTRASONIC ATTENUATION RELATED TO CARRIERS IN HIGH Tc SUPERCONDUCTORS 下载免费PDF全文
For both BiSrCaCuO and TlBaCaCuO samples, internal frictions (Q-1) in the kHz range reveal a plateau (Q-1p) above Tc and a rapid drop below Tc with the turning points located just at Tc for various samples with different Tc. This anomaly cannot be observed in non-superconducting samples. The ultrasonic attenuation (α) in TlBaCaCuO displays similar results to the internal friction. Moreover, it is discovered that the Q-1p is nearly proportional to the carrier density for Y(Pr)BaCuO and Gd(Pr)BaCuO with different Pr contents. These results show that the drop of Q-1 and a below Tc is closely related to superconducting condensation. The Q-1p and αp can be explained using coupling-model of carriers with local dynamic distortion because high Tc superconductors are strong-correlation systems. Furthermore, by taking account of the smearing of superconducting gap structure resulting from the recombination of quasi-particles and by modifying the BCS relative jump rate as S(E, E', Γ) = Re{1-Δ2/[(E-iΓ)(E'-iΓ)]}, the calculated results of internal friction and ultrasonic attenuation below Tc are in good agreement with the experimental data. The superconducting gap Δ and the damping rate Γ for both BiSrCaCuO and TlBaCaCuO have also been obtained, they are in accordance with those got by tunneling spectrum and NMR methods, etc. 相似文献
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本文概括的介绍了近年来我们利用内耗和介电的方法研究铋系铁电材料的一些结果。钛酸铋系铁电体作为一种无铅材料在铁电存储中有着重要的应用,通过对其内部与氧空位有关的力学和电学弛豫行为的测量,并进一步通过对氧空位弛豫及关联行为的研究,揭示了钛酸铋系铁电材料中掺杂、微结构以及铁电性能之间内在的联系。这些结果从微观的角度阐述了影响铁电体剩余极化与铁电疲劳的因素,对于指导并优化现有铁电体的铁电性能有着重要的意义。此外,还报道了对铁电畴、相变等的研究结果,表明力学与介电方法是研究铁电性能及澄清机理的有效手段。 相似文献
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对不同频率下(1 —10 k Hz) Pb( Zr052 Ti048) O3 多晶陶瓷的介电性能的测量表明:在接近铁电相变温度 Tc 以下存在一介电损耗峰,该峰具有弛豫特征但不满足 Arrhenius 关系.这一损耗峰被认为是由于畴界与晶格、缺陷钉扎的互作用引起的.用畴界粘滞运动的动力学方程,考虑陶瓷样品中 Tc 离散分布的情况,模拟了该介电损耗峰在不同频率下的行为,得到了与实验数据一致的结果.并由拟合参数计算了畴界运动的粘滞系数和缺陷钉扎引起的回复力常量. 相似文献
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我们研究了室温下系列Sr掺杂的Y(Ba1-xSrx)2Cu3O7-δ陶瓷样品的63,65Cu核四极共振谱.在YBa2Cu3O7-δ(Y123)中Sr2+的替代会在体系中产生化学压强效应,这种化学压强导致了CuO2平面的Cu(2)核四极共振信号向高频移动,而CuOx链层的Cu(1)核四极共振信号向低频移动.随着Sr2+掺杂的增加,Cu(2)和Cu(1)的核四极共振峰的峰宽都明显地变宽,同时还观察到一个新的Cu核四极共振峰.最后,我们给出了化学压强对超导转变温度的抑制的一些讨论,认为它与CuOx链层氧原子的部分无序导致的载流子非均匀分布或局域化有关. 相似文献
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木文介绍了近两年来我国在高Tc超导氧化物的内耗与超声衰减研究方面的进展.着重介绍了结 构不稳定性的研究、氧缺位引起的弛豫型内耗峰的研究以及磁通钉扎的内耗研究方面的进展. 相似文献