Enhancement of the irreversibility line inYBa2Cu3O6.95single crystals patterned by heavy ion lithography

Abstract

High purity, detwinned YBa 2 Cu 3 O 7−x single crystals were locally irradiated with a stripe pattern using a microcollimated 250 MeV Au ion beam to a dose matching field of B ⌽ = 4 T. Electron microscopy measurements of the cross section of the irradiated crystal indicate the presence of nanometer columnar defects confined to a surface layer ͑blind holes͒ and an ensemble of ancillary defects in the bulk of the crystal. We present systematic studies of the effects of blind hole structures and of ancillary defects using quantitative magneto-optical imaging with a Bi:yttrium iron garnet indicator film. We observed a local reduction in the superconducting critical temperature near the surface layer where the blind holes were formed, due to the high irradiation fluence. The difference in the critical temperature between the surface layer and the bulk of the irradiated stripe zones enabled us to isolate and estimate the enhancement of the local vortex pinning due solely to the ancillary defects induced by the irradiation. We find that the blind holes with the additive contribution of the ancillary defects produce a pronounced upward shift in the irreversibility line and stronger vortex pinning with respect to the unirradiated stripe regions both at low and at high temperatures.

Large enhancement of the in-field critical current density of YBCO coated conductors due to composite pinning landscape

“…The nature of the damage produced under different irradiation conditions in YBCO is well known and understood [31][32][33][34][35][36][37][38]. Numerous studies have been performed on clean single crystals, where the low pre-irradiation J c can be enhanced by orders of magnitude and the interpretation of the resulting J c is relatively straightforward [39][40][41][42][43][44][45][46][47]. However, the use of particle irradiation to improve vortex pinning in coated conductors is relatively unexplored [48][49][50][51][52][53][54].…”