Hysteretic Dependence of Critical Current on Applied Magnetic Field and Magnetic Irreversmujty Line Crossings in Polycrystalline YBa2Cu3C7

1989 ◽  
Vol 169 ◽  
Author(s):  
Thomas R. Askew ◽  
Richard B. Flippen
Keyword(s):  
Magnetic Field ◽  
Critical Current ◽  
Weak Link ◽  
Ac Susceptibility ◽  
Transport Critical Current Density ◽  
High Quality ◽  
Conduction Model ◽  
Trapped Flux ◽  
Magnetic Irreversibility ◽  
Critical Current Density Jc

AbstractThe transport critical current density Jc has been measured in high quality poly-crystalline YBa2Cu3C7 as a function of temperature and for various sweeps of sub-Tesla applied magnetic fields. Large increases over the virgin response were observed in Jc at fields of a few hundred gauss and are attributed to trapped flux in the samples. The amount of trapped flux was measured and correlated to the change at Jc at various temperatures. The position of the magnetic irreversibility line was measured by field induced absorption shift in AC susceptibility. The various data are discussed in the context of the weak link conduction model.

scholarly journals Effect of Magnetic Field on Critical Current Density in Bulk Superconducting Wires

1989 ◽  
Vol 169 ◽  
Author(s):  
M. T. Lanagan ◽  
U. Balachandran ◽  
C. A. Youngdahl ◽  
J. T. Dusek ◽  
J. J. Picciolo ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Weak Link ◽  
Copper Wire ◽  
Superconducting Wires ◽  
Critical Current Density Jc ◽  
The Magnetic Field ◽  
A Current

AbstractBulk YBa2Cu3O7‐x (YBCO) wires and tubes were fabricated by an extrusion technique. Critical current density (Jc) was measured as a function of applied magnetic field at 77 K and was found to decrease significantly in fields below 100 G. Jc was dependent on specimen geometry. In addition, when a concentric magnetic field was generated by passing a current though a copper wire, the external field from the wire could interfere constructively or destructively with the magnetic field produced by current in a YBCO tube. The change in electrical properties with magnetic field has been attributed to weak‐link behavior at the grain boundaries. Batch‐to‐batch differences in the field dependence of Jc imply the possibility of reducing the dependence by processing modifications.

Transport Measurements on Superconducting YBa2Cu3O7-δ Thin Film Lines

1989 ◽  
Vol 169 ◽  
Author(s):  
B. H. Moeckly ◽  
D. K. Lathrop ◽  
G. F. Redinbo ◽  
S. E. Russek ◽  
R. A. Buhrman
Keyword(s):  
Magnetic Field ◽  
Thin Film ◽  
Critical Current ◽  
Weak Link ◽  
High Sensitivity ◽  
Weak Links ◽  
Microwave Response ◽  
Field Response ◽  
Current Densities ◽  
Iv Curves

AbstractCritical current densities, magnetic field response, and microwave response have been measured for laser ablated YBa2Cu3O7-δ thin film lines on MgO and SrTiO3 substrates. Films on SrTiO3 have critical current densities > 1 x 106 A/cm2 at 77K and show uniform transport properties in lines of all sizes. Films on MgO have critical current densities which range between 102 and 106 A/cm2 at 77K and show considerable variation from device to device on the same chip. Narrow lines on MgO with low critical current densities show Josephson weak link structure which includes RSJ-like IV curves, microwave induced constant voltage steps, and a high sensitivity to magnetic field. The presence of the Josephson weak links is correlated with small amounts of misaligned grains in films on MgO.

Effect of Pulsed Magnetic Field Processing on MgB2 Superconductors

2007 ◽  
Vol 546-549 ◽  
pp. 2063-2066 ◽  
Author(s):  
W.X. Li ◽  
Ying Li ◽  
M.Y. Zhu ◽  
R.H. Chen ◽  
H.M. Jin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Pulsed Magnetic Field ◽  
Pinning Force ◽  
Critical Current Density Jc ◽  
Mgb2 Superconductors ◽  
Doped Mgb2 ◽  
Flux Pinning Force

Pulsed magnetic field was first employed in the study on MgB2 superconductors. Superconductivity properties and microstructures of Zn and SiC doped MgB2 were discussed in this paper. The superconductors showed different superconductivities after magnetic sintering. Critical current density and flux pinning force were relevant to the dopants properties in MgB2. Grains in the pulsed magnetic processed MgB2 matrix were smaller than those in the normal processed one. The refinement microstructures have caused the critical current density (Jc) anisotropy in both the Zn and SiC doped MgB2.

DOUBLE STEP BEHAVIOR OF THE CRITICAL CURRENT VERSUS MAGNETIC FIELD IN A BULK JOSEPHSON MEDIUM

1994 ◽  
Vol 08 (24) ◽  
pp. 1483-1491 ◽  
Author(s):  
A.I. D’YACHENKO
Keyword(s):  
Magnetic Field ◽  
Critical Current ◽  
Weak Link ◽  
Surface Current ◽  
Double Step ◽  
Plateau Region ◽  
Josephson Medium ◽  
Metal Ceramic ◽  
Current Value ◽  
Link Model

This paper discusses the physics of the influence of a strong magnetic field H on the high T c metal ceramic critical current J c . The problem of boundary conditions for a surface current value in hard superconductors is analyzed. It is shown that if Abrikosov vortices in granules are rigidly pinned, the J c vs H dependence has a plateau region of relatively constant critical current. The hysteresis of ceramic critical current is calculated on the basis of the Josephson weak link model.

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