Free flotation of the objects can be caused by aerodynamic, acoustic, and optical forces, and can also be generated by electrostatic or magnetic fields or by radio-frequency radiation, as analyzed in detail in ref. In the present work, a typical superconducting levitation due to the Meissner effect is used to lift a superconducting disk by an alternating electromagnetic field. The rotating magnetic field at the position of the hanging sample generates an AC field which is partly shielded by the sample. Therefore, part of the AC magnetic field is expelled from the sample. Since the AC field decreases with increasing height, the expulsion results in a levitation force.
Magnetic levitation counteracts the gravitational force and decreases the weight of the sample.
This explanation can be given for the case when the superconducting disk is rotated by the magnetic field. But it becomes rather difficult to explain the loss of weight when the field is switched off and the disk is still rotating, and the weight of the sample remains decreased till the rotation speed of the disk decreases. The RF rotating field penetrates a specimen to a certain skin depth and induces small currents in the surface of the sample. The RF field is then partly screened from the interior and the sample is expelled from the RF field. This interpretation also seems quite reasonable because the maximum loss of weight of the sample was observed only at high frequencies of the magnetic field up to 106 Hz.