Strong magnetic history dependence of magnetic relaxation in high-Tc superconductors

✍ Scribed by K. Kwasnitza; Ch. Widmer

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 800 KB
• Volume: 184
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(91)90400-s

✦ Synopsis

Very detailed flux creep and relaxation measurements ofintragrain magnetization in sintered high-To superconductors at 4.2 K are presented. The M-relaxation rate is not a single valued function of the applied B-field but depends strongly on the prior magnetic field cycling procedure. The largest relaxation rate is measured on the envelope curves of the M-hysteresis area. On the transition curves (minor loops) the relaxation rate is reduced and even disappears locally. This is of great importance for applications of high-To superconductors in electronics. The results can also be applied to low-To superconductors like NbTi and are of interest for accelerator magnets with superconducting windings.

Theoretical expressions for the relaxation process are derived for all physically relevant parts of the M-hysteresis curve on the basis of Bean's model. As the intragrain M influences also the intergrain critical transport current and microwave absorption in granular high-To material, our results on M-relaxation behavior are a basis to explain the already partly observed time dependence of those phenomena.