Abstract
The levitation force between a permanent magnet and a superconducting thin film was investigated experimentally. The configuration consisted of a cylindrical NdFeB permanent magnet placed above a circular YBa2Cu3O7−δ disk with common cylinder axis. Precise measurements were made of the vertical force F z and the magnetic stiffness κ z as a function of the magnet–superconductor separation at 77 K. Several features contrasting the levitation force produced using bulk superconductors were observed. Thin films produced very high values for F z and κ z per unit volume of superconducting material. The hysteretic behavior of F z during decreasing and increasing separation resulted in loops of nearly symmetrical shape, which also contain a peak in the repulsive force branch. The observations are analyzed and explained with good quantitative agreement using recent theories for flux penetration in thin superconductors in transverse magnetic fields.
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Johansen, T.H., Riise, A.B., Bratsberg, H. et al. Magnetic Levitation With High-T c Superconducting Thin Films. Journal of Superconductivity 11, 519–524 (1998). https://doi.org/10.1023/A:1022618825582
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DOI: https://doi.org/10.1023/A:1022618825582