Magnetic field cancellation on the surface of superconducting rings: Influence on the flux creep

In this work, a study of flux creep in YBCO rings is performed using novel parameters during the induction process. Such rings are obtained from top seeding melt grown samples. To generate the persistent current in the rings, an inducting technique based on the field cooling is used. The main difference versus the traditional method is that the magnetic field is guided through the centre of the ring using a ferromagnetic material. This technique is combined with a magnetic field in opposite direction, which cancels the magnetic field in the surface of the sample and decreases the current decay in the superconducting ring. The decreasing in the decay is produced due to the lower density of vortices trapped in the sample. (C) 2007 Elsevier Ltd. All rights reserved.