Irradiation of YBa2Cu3O7−δ single crystals by 5.6 GeV xenon ions
TL;DR: In this paper, single crystals of YBa2Cu3O7−δ were irradiated at 95 K by 5.6 GeV Xe ions and the evolutions of the superconducting resistive curves were determined in situ as a function of ion fluences.
Abstract: Single crystals of YBa2Cu3O7−δ were irradiated at 95 K by 5.6 GeV Xe ions and the evolutions of the superconducting resistive curves - measured parallel and perpendicular to the c axis - were determined in situ as a function of ion fluences. We find that ϱc and ϱab increase linearly with the fluence and even tend to saturate for the highest fluences. This behaviour strongly differs from that found for sintered samples irradiated under the same conditions for which a quasi-exponential increase of resistance was observed. Nevertheless our results confirm that energy deposition by electronic excitation plays a role in defect creation as previously reported in Xe irradiated sintered samples.
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TL;DR: In this article, the influence of the angular dispersion (splay) of the tracks on vortex pinning and creep is discussed, and measurements of the temperature, field and defect density dependence of the persistent currents and their time relaxation in YBCO are presented.
Abstract: Columnar defects introduced by irradiation with very energetic heavy ions are the most effective pinning centres for flux lines in high-temperature superconductors. This correlated disorder generates large increases in the critical current densities and expansion of the irreversible regime in and the various Bi- and Tl-based compounds. In single crystals and thin films, the pinning enhancement is strongly angular-dependent, and maximizes when the applied magnetic field is parallel to the amorphous latent tracks. In contrast, in the much more anisotropic Bi- and Tl- based materials this unidirectional anisotropy is very small due to the quasi two-dimensional character of the vortices. Some of the extensive experimental studies on this topic are reviewed. Measurements of the temperature, field and defect density dependence of the persistent currents and their time relaxation in YBCO are presented. The analysis of these results based on recent theoretical models permits the identification of various pinning and creep regimes. Studies in other compounds, including technologically relevant Bi-based tapes, are summarized. The influence of the angular dispersion (splay) of the tracks on vortex pinning and creep is discussed.
183 citations
02 Jun 1994-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, a Monte Carlo method is used to describe event by event the interactions of the projectile with the target electrons as well as the evolution of the electronic subsystem of the target.
Abstract: In this paper the swift heavy ion interactions with condensed matter are studied from the point of view of the modifications induced in the electronic subsystem of the target. A Monte Carlo method is used to describe event by event the interactions of the projectile with the target electrons as well as the evolution of the electronic subsystem. The validity of the method and the results are discussed. This detailed picture of the excited target could be used for further explanations and calculations of the damage creation by electronic excitation. We have focused our attention on two materials whose electronic properties are different: graphite and quartz. For both materials a quantitative analysis of the energy deposition mechanism is given.
128 citations
TL;DR: In type-II superconductors the pinning force which determines the critical current density Jc, and the pining energy U which determines thermally activated depinning, in principle are different quantities.
Abstract: In type-II superconductors the pinning force which determines the critical current density Jc, and the pinning energy U which determines thermally activated depinning, in principle are different quantities. Long pinning channels generated by high-energy heavy-ion irradiation, in YBCO can enhance both Jc and U, but in the strongly layered BSCCO they may enhance Jc without enhancing U, since the pancake vortices in the layers depin individually. This is the reason why in BSCCO flux creep is large down to rather low temperatures.
41 citations
TL;DR: In this article, Tl-based superconducting copper oxides were irradiated at 140 K by 3.6 GeV Xe ions and the resistance measured in situ as a function of the fluence.
Abstract: Tl-based superconducting copper oxides Tl 2 Ba 2 CaCu 2 O 8 , TlBa 2 Ca 2 Cu 3 O 9 and Tl 2 Ba 2 Ca 2 Cu 3 O 10 were irradiated at 140 K by 3.6 GeV Xe ions and the resistance measured in situ as a function of the fluence. The results confirm that electronic stopping of GeV heavy ions plays a major role in the defect creation mechanism. Critical current densities were obtained from magnetization measurements on samples irradiated by 5.8 GeV Xe ions at fluences up to 2x10 12 cm -2 and magnetic field orientations parallel and normal to the heavy ions tracks. Large enhancements of flux pinning and J c are observed, in particular at low fluences, without significant change of the T c 's.
36 citations
TL;DR: In this article, the effects of swift heavy ions in materials are reviewed and the effect of high values of the electronic stopping power on phase changes, defect creation and plastic deformation is discussed.
Abstract: The effects of swift heavy ions in materials are reviewed. We present the effects of high values of the electronic stopping power on phase changes, defect creation and plastic deformation.
34 citations
References
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TL;DR: In this article, a formula for the electric tunnel effect through a potential barrier of arbitrary shape existing in a thin insulating film was derived for a rectangular barrier with and without image forces, where the true image potential was considered and compared to the approximate parabolic solution derived by Holm and Kirschstein.
Abstract: A formula is derived for the electric tunnel effect through a potential barrier of arbitrary shape existing in a thin insulating film. The formula is applied to a rectangular barrier with and without image forces. In the image force problem, the true image potential is considered and compared to the approximate parabolic solution derived by Holm and Kirschstein. The anomalies associated with Holm's expression for the intermediate voltage characteristic are resolved. The effect of the dielectric constant of the insulating film is discussed in detail, and it is shown that this constant affects the temperature dependence of the J‐V characteristic of a tunnel junction.
3,727 citations
AT&T1
TL;DR: In this paper, a gettered annealing technique was employed to obtain homogeneous polycrystalline samples of oxygen deficient Ba/sub 2/YCu/sub 3/O/sub 7-sub delta/ for 0less than or equal todeltaless than and equal to 0.7.
Abstract: Employing a gettered annealing technique, we have prepared homogeneous polycrystalline samples of oxygen deficient Ba/sub 2/YCu/sub 3/O/sub 7-//sub delta/ for 0less than or equal todeltaless than or equal to0.7. Measurements of resistive T/sub c/, resistivity, magnetization, and lattice parameter indicate that a distinct bulk superconducting phase with a T/sub c/ of 60 K occurs in the range of 0.3
726 citations
TL;DR: In this paper, a rectangular prism with edges in principal crystal directions is prepared with electrodes on the corners of one face, and voltage-current ratios for opposite pairs of electrodes permit calculation of components of the resistivity tensor.
Abstract: A rectangular prism with edges in principal crystal directions is prepared with electrodes on the corners of one face. Voltage‐current ratios for opposite pairs of electrodes permit calculation of components of the resistivity tensor. The method can use small samples, and is best suited to materials describable by two or three tensor components. Examples are given of measurements of V2O3–Cr and oriented amorphous graphite.
574 citations
TL;DR: In this paper, preliminary phase equilibria diagrams are constructed for the binary systems BaO-{1/2}Y{sub 2}O{sub 3}, BaO -CuO-sub 7-x, and the ternary system BaO
Abstract: Preliminary phase equilibria diagrams are constructed for the binary systems BaO-{1/2}Y{sub 2}O{sub 3}, BaO-CuO{sub x}, {1/2}Y{sub 2}O{sub 3}-CuO{sub x} and the ternary system BaO-{1/2}Y{sub 2}O{sub 3}-CuO{sub x}. Some melting data are used to outline an approximate primary field for the phase responsible for high temperature superconductivity in this system, Ba{sub 2}YCu{sub 3}O{sub 7-x}. A discussion is given of the crystal chemistry of the phase(s) near the composition Ba{sub 3}YCu{sub 2}O{sub x}.
278 citations
TL;DR: In this paper, the authors measured transport anisotropies of superconducting and nonsuperconducting superconductor crystals and showed that classical electron-phonon scattering mechanisms are inadequate.
Abstract: Transport anisotropies of ${\ensuremath{\rho}}_{c}$.${\ensuremath{\rho}}_{\mathrm{ab}}$\ensuremath{\simeq}${10}^{4}$ to ${10}^{5}$ were measured for superconducting and nonsuperconducting ${\mathrm{Bi}}_{2+\mathrm{x}}$${\mathrm{Sr}}_{2\mathrm{\ensuremath{-}}\mathrm{y}}$${\mathrm{CuO}}_{6\ifmmode\pm\else\textpm\fi{}\mathrm{\ensuremath{\delta}}}$ crystals. In superconducting samples ${\ensuremath{\rho}}_{\mathrm{ab}}$ increases linearly with temperature from just above ${T}_{c}$\ensuremath{\simeq}7 to 700 K. The implication of the ${\ensuremath{\rho}}_{\mathrm{ab}}$ results is that classical electron-phonon scattering mechanisms are inadequate. The anisotropy and ${T}_{c}$ for various layered superconductor systems are compared. In all crystals studied ${\ensuremath{\rho}}_{c}$ is nonmetallic, varying as a power law ${T}^{\mathrm{\ensuremath{-}}\ensuremath{\alpha}}$, \ensuremath{\alpha}\ensuremath{\simeq}0.5--1.
176 citations