Radiation induced flux pinning in YBa2Cu3O7-[delta] single crystal
Radiation damage studies have been carried out to determine the changes in superconducting critical current density that result for different choices of radiation direction and magnetic field direction relative to the crystallographic axes. Single crystals of YBa[subscript]2Cu[subscript]3O[subscript]7-[delta] were irradiated with a beam of 200 MeV protons directed either parallel to the a-b plane or parallel to the c-axis. These beams created rather light damage in the form of interstitials and voids that subsequently coalesced to clusters of extra atoms in the a-b plane directed along the (100) direction. For low fluence, the main change was in the c-axis critical current density, J[subscript] c[superscript] c. For fluence in the 10[superscript]12-10[superscript]14 protons/cm[superscript]2 range, J[subscript] c[superscript] c showed a major increase whereas the in-plane critical current density, J[subscript] c[superscript] ab increased much less. There also was a large in-plane anisotropy of J[subscript] c[superscript] c with J[subscript] c[superscript] c five to ten times larger for the field parallel to the damage tracks. For fluences in the range of 10[superscript]16 protons/cm[superscript]2, both J[subscript] c[superscript] c and J[subscript] c[superscript] ab showed large increases to values in the 2 x 10[superscript]6 A/cm[superscript]2 range. Annealing studies at room temperature showed that both J[subscript] c[superscript] c and J[subscript] c[superscript] ab decreased 20 to 30%.