Study of flux-creep in bulk melt-textured YBa2Cu3Ox in the regime of individual pinning

Magnetic relaxation, with magnetic fields applied parallel to the c axis, w as measured in a high-quality melt-textured YBa2Cu3Ox bar. Zero-field-coole d magnetization-versus-time data were obtained within a regime of field and temperatures dominated by single vortex pinning. The activation pinning en ergy U = U-M was calculated from experimental data and compared to U = U(0) ln(J(c)/J), where U, is a constant, J(c) is the critical current density, a nd J the current density. This expression for U obtains within the individu al pinning regime. A logarithmic dependence of U-M on J was found, and the data indicated that a scaling function of U-M, g(T/T-c) = (1 - T/T-c)(1/2), was appropriate for describing the single-vortex pinning regime.