Evaluation of the Effect of Magnetic Flux Sweep Rate on Bulk YBa2Cu3Oy Single Grains Prepared by the Infiltration-Growth (IG) Technique

International audience; The Infiltration-Growth prepared YBa2Cu3O7-y (IG-YBCO) bulks recently received an increase of interest due to a possibility to control the shape and the density as compared to the well-known melt-textured YBCO bulks, IG method also gives the possibility to adapt the synthetization process like preparing a foam [1]–[3] for some particular uses like space applications, when a low-density sample is preferred. To optimize the performance of IG-YBCO an ultrasonic treatment at 300 W was done on the Y-211 powder and for different durations (15, 30, 45 and 60 min) in order to reduce the average grain size. Then, different YBCO bulk single grains were grown using the pre-treated powders with the infiltration-growth technique [4]. Intended for use as trapped field (TF) magnets, previous works were done on samples to evaluate and compare the superconducting properties such as the evaluation of the field dependence critical currents (Jc) or the pinning properties and magnetization loops using an MPMS-SQUID for up to 7 T. But the dependence of the magnetic field sweep rate on the flux creep into the sample and the evaluation of the dynamic relaxation rate is still needed in order to characterize and compare previous high field measurements where a relatively high sweep rate was needed (33 mT/s). Small pieces were cut and mechanically polished (2 x 2 x 0.4 mm3) according to the crystallographic orientation (H // c-axis). Magnetic measurements at various field sweep rates (from 1.25 to 40 mT/s) were done on the samples at various constant temperatures and up to 7 T using MPMS-SQUID in order to determine the impact of the flux creep on the sample properties at high fields such as Jc and irreversible fields (Hirr) as well as the associated dynamic relaxation rate.[1] E. S. Reddy et al., Supercond. Sci. Technol., vol. 15, no. 8, pp. L21–L24, Aug. 2002, doi: 10.1088/0953-2048/15/8/101.[2] J. G. Noudem, et al., Phys. C Supercond., vol. 390, no. 4, pp. 286–290, Jul. 2003, doi: 10.1016/S0921-4534(03)00755-X.[3] M. R. Koblischka et al., IEEE Trans. Appl. Supercond., vol. 29, no. 5, pp. 1–5, Aug. 2019, doi: 10.1109/TASC.2019.2894712.[4] S. Pavan Kumar Naik et al., Appl. Phys. Express, vol. 12, no. 6, p. 063002, Jun. 2019, doi: 10.7567/1882-0786/ab1c72.