Influence of trapped field on the levitation force of SmBCO bulk superconductor

•A new phenomenon was discovered on trapped field dependence of levitation force.•The reliability of levitation force variation trend was confirmed on three samples.•The levitation force variation trend is closely related to the sample's trapped field.

High quality single domain SmBCO bulks superconductor with diameter in 20 mm and thickness in 10 mm were fabricated by the RE + 011 TSIG method in air. The effect of applied magnetic field (Ba) on the trapped field (Btr) and Btr dependence of levitation forces between a permanent magnet (20 mm in diameter, B = 0.5 T) and the SmBCO bulk have been investigated. The results show that the maximum trapped field (Btr,max) of the sample with 0.5 wt% CeO2 increases from 0.17 T to 0.8 T with the increasing of Ba from 0.2 T to 1.4 T, and the fitting equation is achieved, Btr,max is related to Ba: Btr,max=0.613×Ba0.688, and the maximum levitation force shows a complicated variation trend, it increases from 49.4 N to 74.9 N with the increasing of Btr,max from 0 T to 0.43 T, and then decreases from 74.9 N to 69.5 N with the increasing of Btr,max from 0.43 T to 0.58 T, and then increases from 69.5 N to 86.9 N with the increasing of Btr,max from 0.58 T to 0.67 T. This is a very new and first discovered phenomenon on Btr dependence of levitation force compared with the reported results for bulk superconductor. The levitation forces of other two samples were measured and also show a complicated variation trend. And a speculative cause is considered. These results provided a new way which can greatly enhance and control the levitation force by adjusting the trapped field of the sample for practical applications.