Temperature dependence of glassy exponent in YBa2Cu3O7-δ films

Precise measurements of magnetic moment relaxation of YBa2Cu3O7-delta films were carried out in temperature range 4.2 K < T < 80 K at low magnetic field H approximate to 910 Oe. Temperature dependence of the glassy exponent mu of dependence of the activation energy U for vortices motion on current J was analyzed. It was obtained that mu increases from negative values at low temperatures T <= 10 K to mu approximate to 1-2 at T approximate to 40 K and decreases down to negative values at high temperatures T >= 70 K. It was shown that widely used Maley's technique and analysis of T/S(T) vs 1/J(T) dependence are unable to describe correctly strong mu(T) dependence observed in our experiments. (C) 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).