Levitation of Magnets above Superconductors

Abstract

Unlike Type 1 superconductors, Type 2 superconductors can accommodate external magnetic fields at the mixed state; the magnetic flux of the magnet enters the superconductor and is trapped insides. The magnetic field captured by the superconductor depends on the strength of the external magnetic field and the shape of the magnet. The magnetic field trapped in a superconductor is like a shadow of the external magnetic field. Various superconducting experiments can be designed using the mixed state, a typical example of which is the “fishing (suspension) effect.” This chapter introduces various superconducting levitation experiments. These experiments exploit both the perfect diamagnetism and trapped magnetic field in the (superconducting + normal) mixed state of Type 2 superconductors. A description is given of the field-cooling method that traps the magnetic force of the magnet in superconductors and a method for adjusting the position and height of the magnet levitating above a superconductor. Techniques for levitating multiple magnets, toy cars, a fishbowl, and human being above superconductors are also described.