Effect of magnetic field on the transition temperature of high-Tc superconductors in sound velocity measurements

As is shown, thermally assisted vortex motion can come into being in high-T c superconductors due to the applied temperature gradient. Its behavior strongly depends on the local and global microstructure of the samples, moreover on the temperature and magnetic field. Investigation of the density, size and intensity of the pinning centers of specimens leads to the conclusion that the higher homogeneity immediately weakens and the lower one strenghtens the pinning, thus the former promotes and the latter impedes the vortex motion. The non-equilibrium experimental technique together with a.c. susceptibility measurements render possible the direct determination of the velocity of vortices. Depending on the actual microstructural state of samples it has the values between 6 × 10-2 mm/s and 18 × 10-2 mm/s in the case of Y-Ba-Cu-O specimens investigated.

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MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS VI—NON-RESONANT MICROWAVE ABSORPTION IN ULTRA-THIN Bi-Sr-Ca-Cu-O FILMS—

Modern Physics Letters B ◽

10.1142/s0217984992000351 ◽

1992 ◽

Vol 06 (05) ◽

pp. 265-272 ◽

Cited By ~ 4

Author(s):

K. SUGAWARA ◽

T. SUGIMOTO ◽

D.J. BAAR ◽

Y. SHIOHARA ◽

S. TANAKA

Keyword(s):

Magnetic Field ◽

Microwave Absorption ◽

Signal Intensity ◽

Critical Magnetic Field ◽

High Tc Superconductors ◽

Temperature Relation ◽

High Tc ◽

Absorption Studies ◽

Increasing Temperature ◽

Mgo Substrate

Non-resonant microwave absorption (NRMA) studies have been done for Bi-Sr-Ca-Cu-O (BSCCO) films with thicknesses of 30 Å and 15 Å fabricated on MgO substrate by MOCVD. For the latter two kinds of samples have been fabricated: BSCCO/MgO and BiOx/BSCCO/MgO . NRMA signals have been detected up to about 70–75 K for all the samples. The lower critical magnetic field H c1 * of the 30 Å film was severely increased by the application of a magnetic field of several kGauss, whereas it is almost unaffected in the case of 15 Å films. H c1 * increases but the signal intensity decreases with increasing temperature for all the 30 Å and 15 Å samples. The temperature dependence of the intensity is quite different from that of thicker films (100 Å and 350 Å), in which the intensity vs. temperature relation has a peak (or peaks) at particular temperature(s).

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HIGH MAGNETIC FIELD HALL EFFECT AND MAGNETORESISTANCE STUDIES OF Y-Ba-Cu-O: A HIGH Tc SUPERCONDUCTOR

International Journal of Modern Physics B ◽

10.1142/s0217979287000566 ◽

1987 ◽

Vol 01 (02) ◽

pp. 413-417

Author(s):

J.D. Hettinger ◽

A.G. Swanson ◽

J.S. Brooks ◽

Y.P. Ma

Keyword(s):

Magnetic Field ◽

High Temperature ◽

Transition Temperature ◽

Hall Effect ◽

High Temperature Superconductor ◽

Strong Dependence ◽

Zero Magnetic Field ◽

High Tc ◽

Relative Percentage ◽

High Tc Superconductor

We have measured the transition temperature, critical field, magnetoresistance, and Hall effect for the high temperature superconductor Y-Ba-Cu-O in magnetic fields up to 23T in the temperature range 4.2 to 125K. Meissner studies at zero magnetic field were also performed in some cases. We find a strong dependence of these parameters on the relative percentage of the correct phase of Y-Ba-Cu-O in the sample. We report new results on magnetoresistance and Hall effect in these materials.

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