Scaling of the hysteretic magnetic behavior in YBa2Cu3O7 single crystals

Abstract

We have studied the pinning force ${\mathit{F}}_{\mathit{p}}$(B,T) in ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ crystals as a function of fluence of 3-MeV protons. For a given ion-damage level, we could reduce all ${\mathit{F}}_{\mathit{p}}$ data to a single function of reduced field b=B/${\mathit{B}}^{\mathrm{*}}$, where the scaling field ${\mathit{B}}^{\mathrm{*}}$(T)≪${\mathit{H}}_{\mathit{c}2}$(T) is related to the irreversibility line. This result rules out the possibility of matching effects between the vortex lattice and the distribution of pinning sites. We emphasize the influence of thermally activated relaxation in the determination of ${\mathit{F}}_{\mathit{p}}$ and compare the data with simple pinning models.