Effects of Pb-ion irradiation on the vortex pinning in melt-textured YBa 2Cu 3O x

Abstract

Melt-textured YBa 2Cu 3O x quasicrystalline samples were studied for the effects of Pb-ion irradiation on the vortex pinning. The strength of the pinning was monitored by measurements of the saturation remanent magnetization ( M R) as a detailed function of temperature from 4.2 K up to T c (≈92 K). Our results show that M R is greatly enhanced by the Pb-ion irradiation at all temperatures below T c. Specifically, when compared to a similar but nonirradiated sample, the M R of an optimally irradiated sample is raised by a factor of 3.4 at 4.2 K and, more strikingly, by 12.7 at 77 K. Contrastingly, in an earlier study of a γ-ray irradiated Bi 1.6Pb 0.4Sr 2Ca 2Cu 3O 10 sample, the vortex pinning was seen to be enhanced but mainly near 4.2 K, suggesting that the γ-ray irradiation produces highly localized pinning sites. Hence, our present results imply conversely that the Pb-ion irradiation creates extended structural defects that are effective as vortex pinning sites up to relatively high temperatures, including that of liquid nitrogen.