We studied the effects of magnetic field and the temperature on the levitation force for a bulk Gd-Ba-Cu-O superconductor 60 mm in diameter and 20 mm in thickness. Magnetic field distribution in the bulk body was monitored with Hall sensors placed on the sample surface. The sample was placed 10 mm below the magnetic center of a superconducting solenoid coil. The sample was cooled in zero-field mode, and the magnetic field was increased from 0 to 5 T. Therefore, the levitation force which acts downward was measured at various temperatures. After measuring the levitation force, its time relaxation was also measured for 1 h while applying 5 T. The levitation force could be increased with increasing magnetic field in all the temperature range. Lowering temperature was effective in increasing the levitation force and reducing its time relaxation.
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