Orientation and thickness dependence of magnetic levitation force and trapped magnetic field of single grain YBa2Cu3O7-y bulk superconductors

Abstract

2017) Abstract The effects of the crystallographic orientation and sample thickness on the magnetic levitation forces ( F ) and trapped magnetic field ( B ) of single grain YBCO bulk superconductors were examined. Single grain YBCO samples with a (001), (110) or (100) surface were used as the test samples. The samples used for the force-distance ( F-d ) measurement were cooled at 77 K without a magnetic field (zero field cooling, ZFC), whereas the samples used for the B measurement were cooled under the external magnetic field of a Nd-B-Fe permanent magnet (field cooling, FC). It was found that F and B of the (001) surface were higher than those of the (110) or (100) surface, which is attributed to the higher critical current density ( J c ) of the (001) surface. For the (001) samples with t =5 – 18 mm, the maximum magnetic levitation forces ( F max s) of the ZFC samples were larger than 40 N. About 80% of the applied magnetic field was trapped in the FC samples. However, the F and B decreased rapidly as t decreased below 5 mm. There exists a critical sample thickness ( t =5 mm for the experimental condition of this study) for maintaining the large levitation/trapping properties, which is dependent on the material properties and magnitude of the external magnetic