A method comprising irradiating a polycrystalline rare earth metal-alkaline earth metal-transition metal-oxide superconductor layer with protons having an energy of 1 to 6 MeV. The irradiating process produces an irradiated layer that comprises randomly dispersed defects with an average diameter in the range of 1-10 nm.
STATEMENT OF GOVERNMENT INTERESTS
 The United States government has rights in this invention described herein pursuant to Contact No. DE-AC02-06CH11357 between the United States Department of Energy and UChicago Argonne, LLC, as operator of Argonne National Laboratory.