The effect of Zn-substitution and carrier doping on vortex pinning in YBa2Cu3O7-δ single crystals

We measured magnetization of Zn-substituted YBCO single crystals in the overdoped, optimally-doped, and underdoped regimes, and estimated critical current density (J(c)). The Zn-substitution less than 1% enhances the second peak of J(c) in overdoped regime, while it almost suppresses in underdoped regime. The optimized Zn-concentration changes as function of carrier concentration. Carrier-doping increases irreversibility field (H-irr), while Zn-substitution decreases H-irr at all doping levels. It implies that the point defect is not effective pinning center for higher H-irr. (C) 2004 Elsevier B.V. All rights reserved.