Flux Pinning and Peak Effect in Y-123 Superconductor



D. Yoshimi__________, M. Migita, E. S. Otabe, T. Matsushita

Kyushu Institute of Technology, 680-4 Kawazu, Iizuka 820-8502, Japan



  It is well known that Y-123 superconductors have a broad peak in Jc(B) at med*
 *ium fields. It

has been revealed that oxygen deficient regions are relevant to the peak effect*
 *, while 211 particles

are not.  In this paper the elementary pinning mechanism for the peak effect wa*
 *s investigated

for melt-processed Y-123 specimens.  For this purpose, the effect of addition o*
 *f 211 particles

on the peak effect was measured.  A DC magnetization measurement was performed *
 *at various

temperatures using a SQUID magnetometer to estimate the critical current densit*
 *y.  The peak

effect was observed for a specimen without addition of 211 particles.  When 211*
 * particles are

added, the critical current density increased in the low and high field regions*
 *, while it decreased in

the medium field region, resulting in a disappearance of the peak effect. Since*
 * 211 particles act as

attractive pinning centers due to the condensation energy interaction, oxygen d*
 *eficient regions are

considered to act as repulsive pinning centers. The disappearance of the peak e*
 *ffect is speculated

to be caused by an interfere between these pinning centers. A candidate for the*
 * repulsive pinning

mechanism is the kinetic energy interaction under a proximity effect in oxygen *
 *deficient regions

with inferior superconductivity.

  The authors would like to acknowledge Dr. M. Morita of Nippon Steel Corporati*
 *on for prepar-

ing the Y-123 specimens for the measurement.


Mr. Daisuke Yoshimi

c/o Prof. Matsushita

Department of Computer Science and Electronics

Kyushu Institute of Technology

680-4 Kawazu, Iizuka 820-8502, Japan



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