Effect of surface barrier on the vortex relaxation in high-temperature superconductors

The rate of vortex relaxation over the surface barrier in HTSC is found. For the flux exit over the surface barrier the magnetization M depends logarithmically on time whereas for the case of flux entry M is a strongly non-linear function of lnt. The initial relaxation rate, dM/ dlnt, proves to be much larger for flux entry than for exit in contrast to the case of the conventional bulk creep (where these rates are approximately equal). The competitive interplay between such a surface relaxation and the usual bulk one, which results in a crossover in the M(lnt) curve, is duscussed.