We report on the measurements of both vertical and lateral levitation forces between a permanent magnet NdFeB and a polycrystalline YBa 4Cu 6O 7-δ superconductor. The analysis of the obtained results revealed an interesting correlation between the behavior of the forces in the field-cooled and zero-field-cooled regimes, resembling the structure of the so-called susceptibility spectrum χ''(χ'). Such force-force diagrams can be useful for identifying flux distribution structure inside a superconducting material.
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We thank Marcel Ausloos for very useful discussions. The authors gratefully acknowledge Brazilian agencies FAPESP, CNPq, and CAPES for financial support.