Scaling of the flux pinning force in epitaxial Bi2Sr2Ca2Cu3Ox thin films

Abstract

Magnetic-field and temperature dependence of the critical current density ${\mathit{J}}_{\mathit{c}}$ is investigated in epitaxial ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{Ca}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{\mathit{x}}$ thin films. For the magnetic field H applied parallel to the c axis, the flux pinning force density ${\mathit{E}}_{\mathit{p}}$ (=${\mathit{J}}_{\mathit{c}}$B) exhibits clear scaling behavior when H is normalized by the irreversibility field ${\mathit{H}}^{\mathrm{*}}$. The maximum pinning force density scales linearly with ${\mathit{H}}^{\mathrm{*}}$. This is the first observed scaling of ${\mathit{E}}_{\mathit{p}}$ in high-quality thin films of Bi oxides, which we can reasonably explain with flux-creep theory by assuming that the activation energy is proportional to the flux line spacing.