The authors measured the remanent magnetization of superconducting NbTi and MgB2 as a function of time after removing an applied field. At similar reduced temperatures, the density of magnetic flux quanta (fluxons) is found to relax faster in NbTi than in MgB2. Nearer the transition, the relaxation rate in both materials exhibits a saturation that is independent of the initially applied field. This saturation occurs when the distance between fluxons is comparable to the London penetration depth. The temperature dependence of the saturation and time dependence of the relaxation can be characterized by the Anderson-Kim model [Rev. Mod. Phys. 36, 39 (1964)] for fluxon dynamics.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)