Disorder and flux pinning in superconducting pnictide single crystals

Crystalline disorder in the pnictide superconductor PrFeAsO1−y is studied using magneto-optical visualisation of flux penetration, Transmission Electron Microscopy, and X-ray diffraction using synchrotron radiation. Critical-state like flux distributions and the magnitude and temperature dependence of the critical current demonstrate bulk vortex pinning by oxygen vacancies at all temperatures.