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1.
测量了Bi2Sr2CaCu2O8单晶的ab面和c轴方 向电阻,在其超导转变温度附近发现了反常的电阻峰出现.其随外磁场(>100Gs)和电流的增 加而逐渐消失.文章认为这个反常的电阻峰是由于单晶中超导相的不均匀分布而导致的准再 进入行为. 关键词: 2Sr2CaCu2O8单晶')" href="#">Bi2Sr2CaCu2O8单晶 反常电阻峰 准再入行为  相似文献   

2.
本文研究了Bi-Sr-Ca-Cu-O体系中理想成份为Bi_2Sr_2CaCu_2O_8化合物的超导性能和晶体结构。名义成份为BiSrCaCu_2O_(5.5)零电阻超导转变温度T_c(0)=81.5K。用X射线粉末衍射方法测定了Bi_2Sr_2CaCu_2O_8的晶体结构,其基本结构属体心四方晶系,空间群为D_(4h)~(17)-l4/mmm,点阵常数a=3.825A,c=30.82A。每单胞化合式单位为2.2Ca占据2(a)等效点系,4Sr,4Bi和4Cu占据三组4(e)位置,其原子参数z分别为0.110,0.302和0.445,16O分别占据8(g),z=0.445和二组4(e),z=0.210和0.380。Bi_2Sr_2CaCu_2O_8晶体结构可认为是阳离子沿z轴的(00z)和((1/2)(1/2)z)交错排列,由Aurivillius相导生出来的。讨论了在Bi-Sr-Ca-Cu-O体系中可能存在的其它沿z轴不同堆垛层数的超导相。  相似文献   

3.
对高品质单相多晶Bi2Sr2CaCu2O8+δ样品作真空或H2气氛中不同温度下的热处理。由X射线结构分析,其正常态和超导态性质(特别是载流子浓度)的系统测量结果表明:Bi2Sr2CaCu208+δ样品在H2气氛中热处理,其氧的释放可分为两个阶段:一是Bi-O层之间的过量氧原子的逸出,降低系统的载流子浓度,从而调节Tc;二是CuO2面内氧原子的迁移,产生氧空位,使CuO2面内Cu2+的短程二维反铁磁(2D-AFM)有序背景遭到破坏。可以认为:以往文献中报道的Bi2Sr2CaCu2O8+δ超导体的吸氢效应导致Tc的变化,很可能主要的并不是氢原子的电子掺杂行为,而是与吸氢过程中氧含量的变化相联系。 关键词:  相似文献   

4.
使用牛津震动样品磁强计(VSM)研究了Bi2Sr2CaCu2O8单晶的磁滞回线.在20到40K温度之间发现了反常的尖锋效应,随样品O含量的增加,发生尖锋效应的外场也相应提高.可以认为在尖峰效应处发生了由涡漩物质的有序固态到无序固态的相变,在有少量点缺陷存在的BSCCO单晶相图上,Bsp线终止于20K温度处,在20K以下温区没有发生准格子到涡漩玻璃的相变,涡漩固相始终以准格子形式存在;可以认为尖峰效 关键词: 2Sr2CaCu2O8单晶')" href="#">Bi2Sr2CaCu2O8单晶 磁滞回线 尖锋效应 相变  相似文献   

5.
蓝宝石基片上制备大面积Tl2Ba2CaCu2O8超导薄膜   总被引:1,自引:0,他引:1       下载免费PDF全文
在2英寸双面蓝宝石基片上采用CeO2作为缓冲层制备了高质量Tl2Ba2CaCu2O8(Tl-2212)超导薄膜.以金属铈作为溅射靶材,采用射频磁控反应溅射法生长了c轴织构的CeO2缓冲薄膜,并研究了不同生长条件对于CeO2缓冲层的晶体结构及表面形貌的影响.超导薄膜采用直流磁控溅射和后热处理的方法制备.扫描电子显微镜(SEM)图像显示,超  相似文献   

6.
测量了Bi2Sr2CaCu2O8单晶a方向的热电势率Sa和b方向的热电势率Sb与温度T的关系,发现在a-b平面内热电势率存在各向异性。认为Sa与Sb的差异来源于b方向的调制结构,并用扩散热电势率Sd,声子曳引热电势率Sg和相关跳跃热电势率Sh三种贡献,对实验结果进行了 关键词:  相似文献   

7.
精确测量了在不同氧压下退火的单晶Bi2Sr2CaCu2O8+δ(Bi2212)样品的Cu-O面内和Cu-O面外的电阻率ρc(T)和ρab(T).发现ρc(T)和各向异性比(ρc(T)/ρab(T))随着载流子浓度增加而迅速下降.在过掺杂样品中,高于120K时,ρc随温度线性下降,而各向异性 关键词:  相似文献   

8.
Seeking new order parameters and the related broken symmetry and studying their relationship with phase transition have been important topics in condensed matter physics. Here, by using spin-and angle-resolved photoemission spectroscopy, we confirm the helical spin texture caused by spin-layer locking in the nodal region in the cuprate superconductor Bi2Sr2CaCu2O8+δ and discover the anisotropy of spin polarizations at nodes along Γ –X and Γ –Y directio...  相似文献   

9.
本文用粉末烧结法合成了Tl-Ba-Ca-Cu-O体系TlBa2Can-1CunO2n+2.5新系列超导相,用粉末衍射法测定了n=2和3的晶体结构,属简单四方单胞,空间群为D4h1-P4/mmm,点阵常数a相同,而c值不同,随n值而增大。a=3.847?,c分别为12.73?和15.89?,每单胞含一个化合式单位,阳离子沿四方晶系的(0,0,z)和(1/2,1/2,z)位置交替排列,排列的顺序相同,n=3比n=2依次多增加Ca和Cu及相应的氧离子。TlBa2CanCunO2n+2.5,n=3时,零电阻超导转变温度Tc(0)=112K;n=2时,Tc(0)=101K,与Tl2Ba2Can-1CunO2n+4型体心四方晶胞超导相不同,TlBa2Can-1CanO2n+2.5结构中缺氧类钙钛矿型结构单元[Ba2Can-1CunO2n+1]仅被TI-O单层所隔开,当n相同时,Tl-O双隔层的体心四方单胞比Tl-O单层的简单四方单胞的超导转变温度高10K左右,这说明Tl-Ba-Ca-Cu-O体系中超导相的转变温度不仅与类钙钛矿结构单元的[CuO4]和[CuO5]的数目有关,而且与Tl-O的隔层数目有关。 关键词:  相似文献   

10.
YBa2Cu3O7-δ/LaAlO3 (YBCO/LAO) 超导薄膜是通过热蒸发沉积方法制备的,实验中使用的Tl2Ba2CaCu2O8/LaAlO3 (TBCCO/LAO) 超导薄膜是通过直流磁控溅射方法制备的.通过分析两片超导薄膜的XRD谱计算出了两片超导薄膜内的应变,ΔC关键词: YBCO/LAO TBCCO/LAO 超导薄膜 应变 表面电阻  相似文献   

11.
Specific heat data below 1 K of Bi2Sr2CaCu2O8 and YBa2Cu3O7 are analyzed. For YBa2Cu3O7 the nuclear specific heat, CN, amounts to 38T−2 μJ/mol K. CN for Bi2Sr2CaCu2O8 exceeds that of YBa2Cu3O7 by a factor of 15. The nuclear quadrupolar specific heat contribution alone is insufficient to explain the data for YBa2Cu3O7, while lack of NQR data does not allow such a comparison in Bi2Sr2CaCu2O8 to be made. The contribution to CN from nuclear spins coupled via the contact hyperfine interaction with correlated magnetic spins (in the CuO2 plane) is derived as a function of the correlation length. This contribution can be treated independently from the quadrupolar term. We show that the excess specific heat in YBa2Cu3O7 likely originates in a few percentage of an impurity (oxygen deficient) phase with a strong hyperfine field on the Cu nuclei.  相似文献   

12.
We report measurements of anamolously large dissipative conductivities, σ1, in Bi2Sr2CaCu2O8+δ at low temperatures. We have measured the complex conductivity of Bi2Sr2CaCu2O8+δ thin films at 100–600 GHz as a function of doping from the underdoped to the overdoped state. At low temperatures there exists a residual σ1 which scales with the T=0 superfluid density as the doping is varied. This residual σ1 is larger than the possible contribution to σ1 from a thermal population of quasiparticles (QP) at the d-wave gap nodes.  相似文献   

13.
In the present paper, we report a study of the Raman active phonons of Bi2Sr2CaCu2O8 for frequencies extending down to 20 cm−1 and temperatures ranging from 77 to 673 K. In spite of important changes in the spectra occurring under heating, we show that the a---b anisotropy, exemplified by Raman spectroscopy in Bi2Sr2CaCu2O8 and obvious on the macroscopic scale through the crystal morphology, still persists at 673 K. These changes are interpreted in terms of disordering effects in the BiO planes and speak in favor of an order-disorder transition around 500 K.  相似文献   

14.
Flux distributions of partial-melting processed Bi2Sr2CaCu2O8+δ ceramics are obtained using magneto-optic imaging. In remanent states (μ0Ha=0 T), large amounts of trapped flux are observed along (Sr,Ca)2CuOy particles embedded in the Bi2Sr2CaCu2O8+δ matrix. Despite the relatively large size of these particles (up to 30 μm), the pinning effect is similar to that of Y2BaCuO5 particles in melt-processed YBa2Cu3O7−δ. Furthermore, we discuss how the pinning capability of non-superconducting particles of different sizes and densities will show up in magneto-optic images.  相似文献   

15.
We have applied the phenomenological model of diffused interfaces, developed originally to describe the Fe growth on Bi2Sr2CaCu2O8, to interpret quantitatively the core photoemission spectra of two reactive interfaces, namely Cr and Ge on Bi2Sr2CaCu2O8. At room temperature the interfaces with Fe and Cr have the same kinetics of growth suggesting similar adatom condensation, while the semiconductor-superconductor interface grows layer-by-layer according to the Franck-van der Merwe kinetics. Differences in the parameters of the model resulting from the simultaneous fit of the core-level decays are related to differences in the microscopic processes occurring during the growth.  相似文献   

16.
A comparative angle-resolved photoemission measurement has been performed on nonsuperconductive Bi2Sr2Ca0.4Y0.6Cu2O8 and superconductive Bi2Sr2CaCu2O8 to study the nature and origin of the electronic states near the Fermi level. It was found that hole-doping does not cause a rigid shift of the density of states relative to the Fermi level, but creates new electronic states in the vicinity of the Fermi level.  相似文献   

17.
Photoelectron spectroscopy results on single crystals of the superconductors Bi2Sr2CaCu2O8,Bi2Sr2CuO6, Ba0.6K0.4BiO3 and the semiconductor Ba0.9K0.1BiO3 are reported for the photon energy region around the O K absorption threshold. The development of the O-KVV Auger structure has been carefully monitored as a function of photon energy. A non-monotonic behavior displaying a feature at a constant binding energy of about 14 eV was found for Bi2Sr2CaCu2O8 and Bi2Sr2CuO6 in a narrow photon energy region of 1 eV at the main edge of the O K absorption spectrum around 530 eV. The corresponding enhancement, connected with the autoionization of O 2p states, is absent in Ba1−xKxBiO 3 in contrast to Bi2Sr2CaCu2O8 and Bi2Sr2CuO6. The resonant enhancement is more pronounced for Bi2Sr2CuO6 as compared to Bi2Sr2CaCu2O8, which can be explained by a lower charge carrier concentration in the former case, leading to a more localized nature of intermediate O 2p states. The model parameters Cu dd and O pp Coulomb interactions and the charge transfer energy Δ are estimated from the experiments.  相似文献   

18.
The flux-line lattice (FLL) has been observed on the (001) face of high Tc Bi2.2Sr2CaCu2OX and Ti2Ba2CaCu2OX single cristals using the technique of decorating the sample with small ferromagnetic particles. Strong pinning of the Abrikosov vortices by plane defects along (100) and (010) planes has been found out on Bi2.2Sr2CaCu2OX. The triangular FLL with a long-range order has been observed on the perfect Ti2Ba2CaCu2OX single crystal. The penetration depth for a magnetic field parallel to (001) axis has been evaluated as ≤0.2μm at 4.2K for both materials.  相似文献   

19.
We have prepared Bi2Sr2CaCu2Ox/Bi2Sr2CuOx (2212/2201) superlattices with various stacking periodicity by multitarget RF magnetron sputtering. Their crystal structure and electrical properties were investigated. The superlattice was found to be successfully constructed from the data of XRD patterns, AES, etc. The critical temperature increased almost linearly with increasing thickness of the 2212 phase up to a thickness of 6 unit cells. On the other hand, it did not decrease as the thickness of the 2201 layers was increased. The unit cell/unit cell superlattice showed Tc zero of 30 K.  相似文献   

20.
Bi-2222 phases were prepared by solid state reactions and were studied using X-ray diffraction, chemical and EDS-analysis. Compounds with composition Bi2Sr2R1.33Ce0.67Cu2O10+δ were obtained for R=Pr, Nd, Sm-Er. The phases Bi2Sr2Cu2O10+δ with similar structure but without Ce were prepared for R = Pr, Sm-Dy. For Bi2Sr2Eu2−xCexCu2O10+δ the solubility limit was determined and the effect of treatment under different oxygen pressures was investigated. Weak diamagnetic signals (<3%) were detected for some of these samples.  相似文献   

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