Relaxation measurements in the regime of the second magnetization peak in Nb films

✍ Scribed by D. Stamopoulos; D. Niarchos

• Publisher: Elsevier Science
• Year: 2004
• Tongue: English
• Weight: 601 KB
• Volume: 417
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/j.physc.2004.10.009

✦ Synopsis

We report on magnetic measurements as a function of field, temperature and time (relaxation) in superconducting Nb films of critical temperature T c = 9.25 K. The magnetic measurements as a function of field exhibited a ''second magnetization peak'' (SMP) which in general is accompanied by thermomagnetic instabilities (TMIs). The lines H smp (T) where the SMP occurs and the H fj (T) where the first flux jump in the virgin magnetization curves is observed, end at a characteristic point (T 0 , H 0 ) % (7.2 K, 80 Oe). Relaxation measurements showed that for T < T 0 % 7.2 K the activation energy U 0 and the normalized relaxation rate S exhibit non-monotonic behavior as a function either of temperature or field. The extrema observed in U 0 and S coincide with the points H on (T) or H smp (T) of the SMP. In the regime T > T 0 % 7.2 K both U 0 and S present a conventional monotonic behavior. These results indicate that the SMP behavior observed in our Nb films is promoted by the anomalous relaxation of the magnetization.