Correlated pinning properties of heavy ion-irradiated Er123 films

We measured the transport critical current densities in high magnetic fields up to 17 T for Er123 films irradiated by 200MeV Au ion with the matching field of 0.1 T and 1 T along c-axis and 1 T for 23deg tilting from c-axis. The angular dependence of critical current density suggests that the c-axis correlated pinning centers is effective even in much higher magnetic field than its matching field. In addition, we found that the peak of the flux pinning force density (Fp) curves related with the matching field of the columnar defects. The temperature scaling behavior of Fp in field along the defect direction was observed only in low field region below the matching field. Therefore, the c-axis correlated pinning is dominant in low field region. In higher magnetic field than the matching field, however, the c-axis correlated pinning works cooperatively with the background random pinning as well. (author)