HEAVY-ION IRRADIATION EFFECTS IN C-AXIS ORIENTED THIN-FILMS OF YBA2(CU0.9757FE0.03)3O7 STUDIED BY CEMS

Fully c-axis oriented thin films of YBa2(CU0.97Fe0.03)3O7-Fe-57 on [100] SrTiO3 substrate were irradiated with different fluences PHI of 500 MeV I-127 parallel to the c-axis. The samples were investigated by means of x-ray diffraction, resistive T(c) measurements and conversion electron Mossbauer spectroscopy (CEMS). Irradiation results in the appearance of a fourth quadrupole doublet E in the CEMS-spectra (E(Q) = 1.1 mm/s, IS = 0.26 mm/s), whose intensity increases with increasing PHI. The Debye waller factor of the new Fe-species E is only about 60% of that of the species A, B, and C proving that irradiation with high energy heavy ions results in latent tracks of lower density. From the hyperfine parameters of species E we conclude that the latent tracks are mainly formed by the "green phase" Y2BaCuO5. We derived the radius of the latent tracks to be about 26 angstrom.