ELECTRONIC EXCITATION EFFECTS IN ION-IRRADIATED HIGH-T-C SUPERCONDUCTORS

We have measured the fluence dependence of the c-axis lattice paramete r in EuBa2Cu3Oy (EBCO) irradiated with various ions from He to Au over the wide energy range from 0.85 MeV to 3.80 GeV. We have observed a l inear increase of the c-axis lattice parameter with increasing fluence for all irradiations. The slope of c-axis lattice parameter against f luence, which corresponds to the defect production rate, is separated into two contributions; the effect via elastic displacement and the ef fect via electronic excitation. The former contribution exhibits a lin ear increase against the nuclear stopping power, S-n. The latter contr ibution is scaled by the primary ionization rate, dJ/dx, rather than b y the electronic stopping power, S-e, and is nearly proportional to (d J/dx)(4). (C) 1998 Elsevier Science B.V.