On the Determination of Intrinsic Properties of Ceramic High-Tc Superconductors by Ac Susceptibility Measurements

1992 ◽  
Vol 275 ◽  
Author(s):  
F. Ludwig
Keyword(s):  
Sample Size ◽  
Critical State ◽  
Ac Susceptibility ◽  
Field Amplitude ◽  
Critical State Model ◽  
State Model ◽  
Critical Fields ◽  
Current Densities ◽  
Ac Field

ABSTRACTVarious models have been proposed to interpret ac susceptibility curves measured on sintered high-To superconductors (HTSC) and to deduce parameters like critical current densities and critical fields. To get more clearness, systematic studies of position and height of the intergranular maximum in χ'' have been performed on several ceramic HTSC samples in dependence of both ac field amplitude and sample size. In the present paper, the data are used to discuss the various models proposed in the literature. It is shown that modifications of the critical state model using incorrect jc(Hi) functions as well as other interpretations of the χ'' peak yield not actually intrinsic but sample size and geometry dependent parameters. The dependence of both position and height of the intergranular maximum in χ '' on ac field amplitude and sample size can be explained in the framework of a modified critical state model using a power law for the jc(Hi) dependence.

THE Ni INFLUENCE ON THE INTERGRANULAR PROPERTIES OF BULK (Bi,Pb):2223 SUPERCONDUCTOR

1999 ◽  
Vol 13 (11) ◽  
pp. 371-378 ◽  
Author(s):  
A. V. POP
Keyword(s):  
Linear Dependence ◽  
Critical State ◽  
Ac Susceptibility ◽  
Field Amplitude ◽  
Critical State Model ◽  
State Model ◽  
Force Density ◽  
Pinning Force ◽  
Ac Field ◽  
Pinning Force Density

The effect of Ni 3+ ions on the intergranular T p temperature of the imaginary peaks of the ac susceptibility has been studied for a (Bi,Pb):2223 superconductor. The linear dependence of T p as a function of ac field amplitude agree with Muller critical state model. The Ni 3+ ions induced an increase of intergranular pinning force density. J cJ (T) dependence near T c agrees with the assumption of SNS intergrain junctions.

The Fe Influence on the Vortex Response to the AC Field in Bulk (Bi, Pb):2223 Superconductor

1998 ◽  
Vol 12 (27) ◽  
pp. 1117-1124 ◽  
Author(s):  
A. V. Pop
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Critical State ◽  
Ac Susceptibility ◽  
Field Amplitude ◽  
Critical State Model ◽  
Pinning Force ◽  
Fast Decrease ◽  
Ac Field

The effect of Fe 3+ ions on the inter- and intragranular Tp and Tg temperatures of the imaginary peaks of the AC susceptibility has been studied for a (Bi, Pb):2223 superconductor. The linear dependencies of Tp and Tg as a function of AC field amplitude agree with Muller critical state model. The Fe 3+ ions induced a fast decrease of inter and intragranular pinning force densities. The intergrain critical current density J cj calculated from χ″(T) curve is lower in x=0.02 Fe doped sample than in x=0.00 sample. J cj (T) dependence near Tc agrees with the assumption of SNS intergrain junctions.

AC Susceptibility Study of the Inter- and Intragranular Properties in (Bi,Pb):2223 Superconductor

1997 ◽  
Vol 11 (29) ◽  
pp. 3461-3467 ◽  
Author(s):  
A. V. Pop ◽  
R. Deltour ◽  
A. Harabor ◽  
D. Ciurchea ◽  
Gh. Ilonca
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Critical State ◽  
Single Phase ◽  
Ac Susceptibility ◽  
Critical State Model ◽  
State Model ◽  
Susceptibility Study ◽  
Ac Field

The temperature and amplitude of AC field dependencies of both inter-and intragranular T p and T g temperatures of the imaginary peaks of χ′′ has been studied for a sintered single phase (Bi,Pb):2223 superconductor. The AC field dependencies for T p and T g and the relation between inter- and intragrain force densities were discussed by using Müller critical-state model. From the χ′′(T) curve, the values of intergrain magnetic critical current density J cJ was obtained via the application of Bean's critical state model. J cJ (T) dependence near T c agree with the assumption of SNS intergrain junctions.

INFLUENCE OF FLUX CREEP ON AC SUSCEPTIBILITY OF SUPERCONDUCTORS

2005 ◽  
Vol 19 (01n03) ◽  
pp. 139-141
Author(s):  
J. W. LIN ◽  
G. LIU ◽  
X. LENG ◽  
L. ZHANG ◽  
S. Y. DING
Keyword(s):  
Critical State ◽  
Ac Susceptibility ◽  
Flux Creep ◽  
Critical State Model ◽  
State Model ◽  
Ac Field

Influence of flux creep on ac susceptibility (acs) of a superconductor was examined by simulation. Comparing the acs with and without flux creep, it was found that frequency of ac field shifted the acs with flux creep but did not affect the acs of critical state model. In addition, the amplitude of ac field and dc field affect differently for the two models.

EFFECT OF THE Fe AND Zn CODOPED ON THE INTERGRANULAR PROPERTIES FOR (Bi1.6Pb0.4)(Sr1.8Ba0.2)Ca2(Cu1-x-yZnxFey)3Oz SUPERCONDUCTING SYSTEM

2002 ◽  
Vol 16 (08) ◽  
pp. 1255-1259 ◽  
Author(s):  
A. V. POP ◽  
V. POP
Keyword(s):  
Magnetic Field ◽  
Linear Dependence ◽  
Critical State ◽  
Ac Susceptibility ◽  
Field Amplitude ◽  
Critical State Model ◽  
Force Density ◽  
Pinning Force ◽  
Ac Field ◽  
Pinning Force Density

Systematic measurements of the AC susceptibility as a function of temperature and magnetic field amplitude H ac for the Fe and Zn codoped ( Bi 1.6 Pb 0.4)( Sr 1.8 Ba 0.2) Ca 2( Cu 1-x-y Zn x Fe y)3 O z (x = 0.00;0.02 and y = 0.00;0.01) system are reported. Above H ac = 200 A/m, the linear dependence of T p for maximum of imaginary χ′′(T) peak as a function of AC field amplitude agree with Muller critical state model. The intergrain pinning force density decreases in doped and codoped samples.

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