AMPLITUDE-DEPENDENT MAGNETIC STIFFNESS OF MELT-QUENCHED YBA2CU3O7-DELTA SUPERCONDUCTORS

Experimental results are reported the differential levitation forces ( magnetic stiffness) between permanent rare-earth magnets and high-temp erature superconductors. Using a clamped beam cantilever, the amplitud e-dependent magnetic stiffness for five configurations of the test mag nets has been investigated for the melt-quenched YBa2Cu3O7-delta (Y123 ) superconductors in a range of 1 mu m-1 mm. The configuration where t he moment of the magnet and the direction of motion are perpendicular to the upper surface of the superconductor has the highest stiffness v alue among the five configurations. Compared with the data from a sint ered Y123 superconductor, the magnetic stiffness for the melt-quenched materials has a much higher value and a much weaker dependence on the oscillation amplitudes. The results are compared with the current exp erimental and theoretical results.