Effects of the relative speed of a magnet moving to and from a single-domain YBCO bulks on their interaction force

Two single-domain YBCO bulks with different grain orientations were used to investigate the effect of relative moving speed between the magnet and YBCO bulk, on their interaction force at LN₂ temperature under zero field cooling (ZFC) state. It is found that the levitation force of the sample S1 with c-axis perpendicular to the top surface is higher than that of the sample S2 with c-axis parallel to the top surface; the maximum levitation force (F_ML) is increasing with the increase of relative moving speed (V_RMS) between the magnet and the samples at first and reaches a peak value for sample S1 and a peak zone values for sample S2, then the F_ML decreases with the increase of V_RMS; the stiffness between the samples and the magnet is decreasing with the increase of the V_RMS. This result is useful for the application of superconducting levitation.