YBa2Cu3O7—x和GdBa2Cu3O7—x薄膜中的涡旋玻璃转变的观察

本给出了具有高密度孪晶界ｃ取向ＹＢａ２Ｃｕ３Ｏ７－ｘ外延薄膜存在涡旋玻璃转变及很好的标度行为的实验证据，在有ａ方向昌粒或４５°晶界的ＧｄＢａ２Ｃｕ３Ｏ７－ｘ外延薄膜中存在涡旋玻璃转变但在转变温度附近观察到磁通蠕动和热激活磁通流的某些特征。     

YBa2Cu3O7—x超导体的制作

本文译自Asia—Pacific Physics News(Vol.2,1987年11月),原编者指出制作高温超导体是很容易的,美国、日本和英国的中学生已经制作出了他们自己的样品。并认为这也是发展中国家的中学,在力所能及的范围内,接触物理学尖端领域的少数几个实验之一。文中介绍的配方是1987年6月19日由美国物理教师联合会(AAPT)的会议制订的。     

μSR Study of Zn-Substituted YBa2Cu3O x

We report zero field and transverse fieldSR. measurements in magnetic YBa₂(Cu_1–y Zn _y )₃O _x . Mild disorder of the antiferromagnetic state (x<6.1), a new disordered magnetic phase abovex=6.4 where superconductivity is destroyed by Zn substitution and, finally, local moments in the paramagnetic state are the most salient features related to Zn substitution described here.     

Magnetic order in Sr x Ca1−x Cu0.99 57Fe0.01O2

Sr _x Ca_1–x Cu_0.99 ⁵⁷Fe_0.01O₂ was studied forx=0.13, 0.15, and 0.17. Mössbauer spectroscopy and magnetization measurements indicate magnetic ordering characteristic of spin glass systems withT _f70K forx=0.15 and 0.13.     

μSr and vortex pinning in Bi2Sr2Ca1−x Gd x )Cu2O y

We present transverse fieldSR and bulk magnetisation studies on powders of Bi₂Sr₂(Ca_1{itxGd _x )Cu₂O _y for 0x<0.5. We have found that the effective pinning decreases rapidly withx even for values ofx for whichT _c remains unchanged. We have interpreted this decrease in terms of changes in _ab (obtained fromSR) which cause a decrease in vortex-vortex interactions. The field distribution spectra in these superconductors have been obtained using a maximum entropy analysis and are found to agree with the calculations by Harshmanet al.     

Thermal conductivity anomalies in GdBa2Cu3O7−x

The measurements of the thermal and electric conductivity of three GdBa₂Cu₃O_7−x samples with different orthorhombic distortions are presented. The electronic component of the total conductivity in the normal state is evaluated. Its value is connected with the magnitude of the change of the slope of the total conductivity λ for the critical temperature T_c.     

Superconducting cluster in YBa2Cu3O7−x ceramic

The method of point laser heating of a sample is used to perform experimental investigations of the electrical conductivity of YBa₂Cu₃O_7−x ceramic in the vicinity of its critical state. It is found that, in the vicinity of transition to the superconducting state, the electrical conductivity of the ceramic exhibits a clusterlike behavior substantially nonuniform over the sample cross section. The topology of a superconducting cluster is investigated, as well as its spatial localization in the sample. A model of the formation of a superconducting cluster in a ceramic superconductor is suggested.     

Phonon transport in superconducting EuBa2Cu3O7−x

We have measured the thermal conductivity, Young modulus sound velocity and internal friction of a polycrystalline sample of the ceramic superconductor EuBa₂Cu₃O_7-x. The low temperature data can be quantitavely understood assuming the interaction of phonons with tunneling systems.     

Normal state resistivity of YBa2Cu3O7−x

A systematic study has been carried out on the normal state resistivity of YBa₂Cu₃O_7–x . Samples were cut from the same well-annealed material and were quenched from different temperatures (T _Q ). The resistivity is metallic whenT _Q 500 °C and becomes semiconductor-like whenT _Q 600 °C. The data on the latter was interpreted in terms of the three-dimensional localization model proposed by Mott.The work at USCD was supported by the California MICRO program     

Magnetic properties of superconducting EuBa2Cu3O7−x

The magnetic properties of superconducting EuBa₂Cu₃O_7–x with resistiveT _c 96.5 K are measured. The normal state magnetic susceptibility is analyzed within the framework of the Van Vleck-Frank theory, leading to the conclusion that the strong moments of the Eu³⁺ ions are uncorrelated, and do not affect the superconducting state.     

Misfit stresses in YBa2Cu3O7−x films

Misfit and thermoelastic stresses in HTSC layers 1-2-3 grown on various substrates are, analyzed with the use of ultrasonic measurements of Young's moduli inYBa ₂ Cu ₃ O _7−x . It is shown that the misfit stress gives the main contribution to the formation of the HTSC layer strain. Military Academy of Strategic Rocket Forces. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 87–90, April, 2000.     

Peculiarities of magnetic flux penetration and trapping in monocrystalline (YBa2Cu3O7−x and Bi2Sr2CaCu2O8+x ) and polycrystalline (YBa2Cu3O7−x ) samples

A comparative analysis of the magnetic flux trapping in monocrystalline and polycrystalline HTSC samples is carried out, and the possibility of employing the dependence of the trapped magnetic flux on the external magnetic field for obtaining comparative estimates of the effect of pinning centers is determined.     

Ag／YB12Cu3O7—x,Al／YBa2Cu3O7—x界面特性分析

利用电学测量方法结合二次离子质谱（ＳＩＭＳ）技术对金属Ａｇ与Ａｌ与ＹＢａ２Ｃｕ３Ｏ７－ｘ（ＹＢＣＯ）超导薄膜接触界面电学性质和扩散特征进行了测试分析，分析结果显示由于Ａｇ和Ａｌ具有不同的化学性质，二与ＹＢＣＯ界面的互扩散特性有明显不同，这些不同影响到接触界面的电学性质和接触窗口下ＹＢＣＯ超导性能，在Ａｇ／ＹＢＣＯ样品中，在高于３５０℃以上的温度下氧气氛中退火将引起Ａｇ和Ｏ的界面互扩散，但对ＹＢＣ     

Transition to gapless superconductivity in YBa2(Cu1−x Zn x )3O7

Point-contact spectra of YBa₂(Cu_1–x Zn _x )₃O₇/Ag are studied at various temperatures. The differential resistance dV/dI of the point contacts shows gap-related structures belowT _c which can be attributed to Andreev reflection. Evaluation of many spectra for each sample taken at 4.2 K yields a wide distribution of voltages /e at which these structures occur. The upper limit varies roughly as expected from the depression ofT _c by Zn-doping from /e=29 mV (x=0) to 9 mV (x=0.05), while the lower limit decreases much faster and disappears forx=0.05. Hence, the Zn doped samples exhibit a tendency to gapless superconductivity as suggested earlier on the basis of specific-heat measurements.     

A simple statistical phenomenological model for cation substitutions in Nd1+ x Ba2− x Cu3O7−δ+ x /2

The first results are presented of calculations using a quite simple phenomenological model developed to simulate the cationic substitutions in Nd_{1+ x} Ba_{2? x} Cu₃O_{7+ x /2?δ} (Nd123). Although elementary concepts from statistical mechanics are used in the model, significant results have been obtained, such as the reconstruction of the substitution region limits and their dependence on temperature. Particularly interesting is the prediction of strong temperature dependence for the minimum substitution parameter, x _min.     

Optical Properties of Films of Cu x Ag1−x InSe2 Solid Solutions Obtained by Laser Evaporation

The structure and optical properties of the films of ternary compounds AgInSe₂, CuInSe₂ and Cu _x Ag_1–x InSe₂ solid solutions obtained by pulsed laser evaporation are investigated. It has been established that the films like bulk crystals have the structure of chalcopyrite. By the transmission and reflection spectra near the edge of natural absorption the refractive index and coefficient of optical absorption are calculated and the energies of interband transitions and the crystalline and spinorbit splitting are determined.     

GdBa2Cu3O7—x超导体失氧与超导电性的关系：GdBa2Cu3o7—x淬火样品的EXAF …

本文采用ＥＸＡＦＳ方法了ＧｄＢａ２Ｃｕ３Ｏ７－ｘ高Ｔｘ超导陶瓷在不同温度下淬火后各金属原子周围氧配位数及键长的变化,得出该１２３相超导体随淬火温度升高失氧的具体位置为Ｏ１及Ｏ４,Ｃｕ－Ｏ平面未被破坏。指出Ｃｕ－Ｏ链及Ｏ４在１２３相超导体中应具有重要作用。     

ARXPS-studies ofĉ-axis textured — superconducting YBa2Cu3O x -films

YBa₂Cu₃O _x sputter deposited cold on Al₂O₃ and on MgO grows in O₂ annealing epitaxially to a transparent, superconducting film withT _c=80 K. The unscraped surfaces of these films are smooth showing XPS lines changing with photoelectron take-off angle. This enhanced data base allows to separate the different chemical shifts and to obtain their spatial distribution. This yields the identification of the chemical compounds (hydroxide, peroxide, carbonate, carboxyle, cuprate, graphite ...), their amount and their distribution making up the cinder and the cuprate. The cinder grows with O₂-anneal at internal and external surfaces. Because of the large unit cell and of the anisotropy of the cuprate the chemical composition of the surface depends on orientation and changes over distances of the order of 1 nm.The cinder stoichiometry gives insights in the chemistry going on in O₂ annealing. Below the cinder the signature of-axis textured YBa₂Cu₃O _x surfaces are identified, showing that a Ba-oxide layer forms the stable surface. This Ba-oxide-surface coats Cu-oxide and Y-oxide layers yielding so an intrinsically insulating surface layer of about 1 nm thickness. In superconducting cuprates a metallic Ba-level shift occurs as compared to the Ba in oxides or cuprate surfaces or insulating cuprates, whereas Y does not show such a metallic chemical shift in the transition to superconducting cuprates. This asks new questions about charge transfer and superconducting interaction in the grains and the coupling between them.