We have studied magnetic properties of a single grain Gd-Ba-Cu-O bulk superconductor 140 mm in diameter. The distribution of the trapped magnetic field showed that the sample was a single domain without serious weak links. The maximum trapped magnetic field at 65 K was 3.66 T, when the bulk was field-cooled in 4 T. From the distribution measurements of the trapped magnetic field, it was confirmed that a large amount of flux could be trapped in a large grain superconductor. In addition, the magnetic field could reach a longer distance in a large bulk compared to smaller samples. The repulsive force measurements also showed that the repulsive force density of the larger bulk was much larger than those of smaller samples.
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