Restricted reversible region and strongly enhanced pinning in MPMG YBa2Cu3O7 with Y2BaCuO5 inclusions

Sagdahl, L.T.; Lægreid, T.; Fossheim, K.; Murakami, Masato; Fujimoto, Hiroyuki; Gotoh, S.; Yamaguchi, Koji; Yamauchi, H.; Koshizuka, N.; Tanaka, Shōji

doi:10.1016/0921-4534(91)90220-s

Cited by 26 publications

(5 citation statements)

References 16 publications

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“…With decreasing amplitude h", the energy U(j) is increased and the temperature where the dissipation peak occurs is shifted to higher values, which is in agreement with experimental data of Krusin-Elbaum et al (1991) and of Sagdahl et al (1991). Note that, reversing the above argumentation, we can also say that Eq.…”

Section: Lock-in Transitionsupporting

confidence: 82%

Vortices in high-temperature superconductors

et al. 1994

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With the high-temperature superconductors a qualitatively new regime in the phenomenology of type-II superconductivity can be accessed. The key elements governing the statistical mechanics and the dynamics of the vortex system are (dynamic) thermal and quantum fluctuations and (static) quenched disorder. The importance of these three sources of disorder can be quantified by the Ginzburg number Gi =(T, /H, sg ) /2, the quantum resistance Qu =(e /A'i(p"/ski, and the critical current-density ratio j,/jo, with j, and jo denoting the depinning and depairing current densities, respectively (p" is the normal-state resistivity and E = m /M (1 denotes the anisotropy parameter). The material parameters of the oxides conspire to produce a large Ginzburg number Gi -10 and a large quantum resistance Qu -10 ', values which are by orders of magnitude larger than in conventional superconductors, leading to interesting effects such as the melting of the vortex lattice, the creation of new vortex-liquid phases, and the appearance of macroscopic quantum phenomena. Introducing quenched disorder into the system turns the Abrikosov lattice into a vortex glass, whereas the vortex liquid remains a liquid. The terms "glass" and "liquid" are defined in a dynamic sense, with a sublinear response p=BE/Bji c characterizing the truly superconducting vortex glass and a finite resistivity p( j~0))0 being the signature of the liquid phase. The smallness of j,/jo allows one to discuss the influence of quenched disorder in terms of the weak collective pinning theory. Supplementing the traditional theory of weak collective pinning to take into account thermal and quantum fluctuations, as well as the new scaling concepts for elastic media subject to a random potential, this modern version of the weak collective pinning theory consistently accounts for a large number of novel phenomena, such as the broad resistive transition, thermally assisted flux flow, giant and quantum creep, and the glassiness of the solid state. The strong layering of the oxides introduces additional new features into the thermodynamic phase diagram, such as a layer decoupling transition, and modifies the mechanism of pinning and creep in various ways. The presence of strong (correlated) disorder in the form of twin boundaries or columnar defects not only is technologically relevant but also provides the framework for the physical realization of novel thermodynamic phases such as the Bose glass. On a macroscopic scale the vortex system exhibits self-organized criticality, with both the spatial and the temporal scale accessible to experimental investigations.

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Section: Lock-in Transitionsupporting

confidence: 82%

Vortices in high-temperature superconductors

et al. 1994

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“…It is clear that the defect density is very small around the 211 particle, suggesting that the 211 itself contributes to flux pinning. It has also been found that the irreversibility line can be shifted to higher temperatures [24] and the flux creep rate can be reduced by 211 doping [5], which also supports the fact that the 211 particles are effective pinning centers.…”

Section: Journal Of Engineering Materials and Technologymentioning

confidence: 71%

Melt Processing of Bulk YBaCuO Superconductors With High Jc

Murakami

Kondoh

Fujimoto

et al. 1992

Journal of Engineering Materials and Technology

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There are several melt processes which promote high J c in bulk YBaCuO. A comparison of various melt processes was performed in this study. It was found that size control of the Y 2 BaCuO s inclusions is the key to the improvement in J c values. IntroductionOxide superconductors are very attractive since they have high critical temperatures, which enables the use of liquid nitrogen as a coolant. However, for most applications of superconductors, critical current densities (J c 's) of 10 4 -10 6 A/cm 2 are required in the presence of significant magnetic fields. It was once believed that the J c values of oxide superconductors were intrinsically small and their applications were extremely limited [1].There are three major problems in oxide superconductors for obtaining high J c at high temperatures: (1) weak links; (2) low flux pinning force; and (3) thermal activation. As long as the superconductors are used at high temperatures, thermal

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“…When the applied magnetic field is perpendicular to the surface of the superconductor, the upper critical field is truly B c2 . When it is parallel to the surface, however, it turns out that the superconducting state can persist in a thin surface sheath for applied surface fields up to the higher value B c3 5 1.69 B c2 (Saint-James and de Gennes, 1963;Saint-James et al, 1969;Van Duzer and Turner, 1981, p. 319;Walton et al, 1974;Yuan and Whitehead, 1991). 363 Type II superconductivity The temperature dependence of the thermodynamic critical field B c is given in Chapter 2, Section XIII.…”

Section: Superconductivitymentioning

confidence: 98%

“…A pinning force F p is a short-range force that holds the core of a vortex in place at, inter alia, a point defect (Giapintzakis et al, 1992;Hylton and Beasley, 1990), columnar defect (Nelson and Vinokur, 1992;Prost et al, 1993), screw dislocation (Ivlev and Jin et al, 1991), oxygen vacancy (Chudnovsky, 1990;, inclusion (Murakami et al, 1991;Sagdahl et al, 1991;Shi et al, 1989Shi et al, , 1990a, grain boundary (Muller et al, 1991b), twin boundary (Kwok et al, 1990a;Lairson et al, 1990a,b;Liu et al, 1991b;Svensmark and Falicov, 1990), intragranular or intergranular nonsuperconducting region Jung et al, 1990), or praseodymium (Pr) doping (Paulius et al, 1993;Radousky, 1992). The density of pinning centers can be high, with average separations of 100 Å or less (Martin et al, 1992;Tessler et al, 1991).…”

Section: B Pinningmentioning

confidence: 98%