Microwave response and surface impedance of weak links

1997 ◽  
Vol 56 (22) ◽  
pp. 14723-14732 ◽  
Author(s):  
J. McDonald ◽  
John R. Clem
Keyword(s):  
Surface Impedance ◽  
Weak Links ◽  
Microwave Response

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.

On Extrinsic Effects in the Surface Impedance of Cuprate Superconductors

1992 ◽  
Vol 275 ◽  
Author(s):  
J. Halbritter
Keyword(s):  
Field Dependence ◽  
Surface Impedance ◽  
Cuprate Superconductors ◽  
Nonlinear Effects ◽  
Weighting Factor ◽  
Weak Links ◽  
Flux Flow ◽  
Unique Method ◽  
Rf Devices ◽  
Thin Seam

ABSTRACTPresently, the rf surface impedance Z of cuprate superconductors is still shrinking with material improvements, which is shown clearly by Z = Z1+Zres still dominated by extrinsic properties summarized in Zres. We present evidence that Zres is due to the large leakage current jbi and the small critical current jcj of weak links. The latter destroys the intrinsic shielding from a λ1 -thin seam λJ deep into the bulk. This causes rf residual losses Rres ≈ (ΩμO)2λJ3 σb1/2. Rres stays finite at T≃O by σb1(T→O)≈σb1(αjb1) being amplified by (λj/λ1>103 as a weighting factor. An appropriate measure of weak links is the grain boundary resistance Rbn(∝ρ(O)) enhancing λj ∝ Rbn and Rres ∝ Rbn2. Thus, Zres is minimal for minimal extrapolated normal conducting resistivity ρ(T→O).To identify the weak links as new entity the H-field dependence is most helpful, because at very low fields Hc1J∝ 1/λJ Josephson fluxons penetrate into the weak links. These Josephson fluxons show negligible flux flow or flux creep, and enhance Zres by λJ(H, T) ∝ l/√Jjc (H, T). The measured JcJ (H, T) - and Jbl - values explain Zres quantitatively as well as in temperature ∝ ( a+ Tn) (n ≈ 1, T<Tc/2) and in field ∝ (b + Hn) (n≈1, H>Hc1J) dependence being thus a unique method to obtain the different Hc1-values. The strength of the field dependence d Zres/dH ∝ Zres (Hc1J*)/Hc2J(T) is not only a measure of Zres and HC2j(T) but is crucial for nonlinear effects and (fluxon) noise also, which limits the performance of rf devices.

scholarly journals Effects of Weak Links in the Nonlinear Microwave Response of MgB2 Superconductor

2007 ◽  
Vol 20 (1) ◽  
pp. 13-20 ◽  
Author(s):  
A. Agliolo Gallitto ◽  
G. Bonsignore ◽  
G. Giunchi ◽  
M. Li Vigni
Keyword(s):  
Weak Links ◽  
Mgb2 Superconductor ◽  
Microwave Response

A new type of defect structure in 124-superconducting oxide revealed by HREM

1991 ◽  
Vol 49 ◽  
pp. 1092-1093
Author(s):  
R. Sharma ◽  
B.L. Ramakrishna ◽  
N.N. Thadhani ◽  
D. Hianes ◽  
Z. Iqbal
Keyword(s):  
Shock Wave ◽  
Defect Structure ◽  
Neutron Radiation ◽  
Weak Links ◽  
Defect Structures ◽  
New Materials ◽  
New Type ◽  
Current Densities ◽  
Processing Techniques ◽  
Microstructural Studies

After materials with superconducting temperatures higher than liquid nitrogen have been prepared, more emphasis has been on increasing the current densities (Jc) of high Tc superconductors than finding new materials with higher transition temperatures. Different processing techniques i.e thin films, shock wave processing, neutron radiation etc. have been applied in order to increase Jc. Microstructural studies of compounds thus prepared have shown either a decrease in gram boundaries that act as weak-links or increase in defect structure that act as flux-pinning centers. We have studied shock wave synthesized Tl-Ba-Cu-O and shock wave processed Y-123 superconductors with somewhat different properties compared to those prepared by solid-state reaction. Here we report the defect structures observed in the shock-processed Y-124 superconductors.

Nonlinear microwave response of a YBaCuO

1992 ◽  
Vol 2 (3) ◽  
pp. 355-372 ◽  
Author(s):  
M. R. Trunin ◽  
G. I. Leviev
Keyword(s):  
Microwave Response

PONDEROMOTIVE EFFECT OF ELECTROMAGNETIC WAVES ON THIN VIBRATORS WITH WEAKLY PERTURBED SURFACE IMPEDANCE

2020 ◽  
Vol 79 (14) ◽  
pp. 1205-1215
Author(s):  
Yu. M. Penkin ◽  
V. A. Katrich ◽  
M. V. Nesterenko ◽  
S. L. Berdnik
Keyword(s):  
Surface Impedance ◽  
Electromagnetic Waves
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