Cryst. Res. Technol. 44, No. 2, 206 – 210 (2009) / DOI 10.1002/crat.200800365 © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim The influence of Pb-ion irradiation on melt-textured YBa 2 Cu 3 O x crystals I. M. Obaidat* 1 , B. A. Albiss 2 , H. Claus 3,4 , M. Gharaibeh 2 , and M. K. Hasan 2 1 Department of Physics, United Arab Emirates University, Al-Ain 17551, United Arab Emirates 2 Department of Physics, Jordan University of Science and Technology, Irbid 22110, Jordan 3 Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA 4 Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607-7059, USA Received 12 August 2008, revised 4 September 2008, accepted 5 September 2008 Published online 25 October 2008 Key words melt-textured crystals, Pb-ion irradiation, vortex pinning. PACS 74.60.Ge, 74.70.Jm Melt-textured YBa 2 Cu 3 O x crystals have been irradiated along the c-axis with 208 Pb 56+ ions corresponding to dose matching fields, B Φ = 0.5 T and B Φ = 2.0 T. Magnetization measurements were conducted along the ab plane of the samples. The strength of pinning sites was investigated by measuring magnetization hysterisis and the saturation remanent magnetization M R at several temperatures. We have found that the pinning strength was considerably enhanced after irradiation at both doses. Interestingly, the pinning strength at a Pb- ion irradiation which corresponds to the dose matching field B Φ = 0.5 T, was found to be significantly larger than that at the dose matching field B Φ = 2.0 T at all temperatures. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 Introduction The pinning strength of vortices in high-temperature superconductors (HTSCs) is known to be fairly weak compared to the pinning strength in conventional type-II superconductors, especially at high temperatures [1]. Since the critical current density J c , is crucially important in the applications of HTSCs, huge scientific research have been conducted to optimize J c values. Introducing artificial pinning centers in the HTSCs using several types of energetic radiations was found to be very successful in increasing the vortex pinning forces [2- 9]. Irradiating the HTSCs by heavy ions creates extended structural (columnar) defects in the material. Because the columnar defects can pin a vortex along its whole length, they are considered to be effective vortex pinning sites (even at high temperatures). This increase of pinning strength due to the columnar defects is expected to enhance the critical current density [2,3]. In this paper we report on magnetization measurements that were conducted along the ab plane of melt- textured YBa 2 Cu 3 O x crystals that have been irradiated along the c-axis with 208 Pb 56+ ions with two different doses. Significant increase of vortex pinning strength was found after irradiation. The lower dose of Pb-ion irradiation was found to have more effect on the pinning strength of the samples. 2 Experimental Our YBCO crystalline samples were circular disks, 2 mm in diameter, 0.1 mm thick, which had been cut from a melt-textured YBCO platelet [10,11]. The crystallographic c axes of the samples were aligned normal to the disk planes. One sample (S1) was left without irradiation. Two other samples (S2 and S3) were irradiated with 208 Pb 56+ ions along both opposite directions along the c axis, since the penetration depth of the irradiation was ____________________ * Corresponding author: e-mail: iobaidat@uaeu.ac.ae