Superdiamagnetism

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The Meißner effect using a high-temperature superconductor and powerful Rare-earth magnet ^[1].

Superdiamagnetism is the cause of superconducting magnetic levitation, and is a phenomenon occurring in some materials at very low temperatures. Experiments carried out to show superdiamagnetism involve immersing a superconductor in liquid nitrogen (LN₂). This cools the superconductor below the transition temperature, at which point the thermodynamic state of superconductivity is observed, facilitating superdiamagnetism.

Superdiamagnestism is caused by the resulting magnetic field formed when a magnet induces a screening current in a superconductor. This induced magnetic field directly opposes the original field, and, as there is no electrical resistance in the superconductor, the 'eddy current' induced in the superconductor do not decay ^[2]. The observation described in this paragraph is called The Meißner effect.

[edit] Flux pinning

Flux pinning or "the flux-trapping effect" is the phenomenon occurring in Type II superconductors whereby the magnetic flux lines do not move ^[3]. In terms of experimental observations, flux pinning is characterised by a superconductor 'preferring' to stay at a specific distance from the source of the magnetic field (i.e. at the point where the trapped flux lines match those of the magnetic source, the forces of attraction and repulsion between the superconductor and magnetic source are equal).

The magnetic source will 'hover' above the superconductor (or the superconductor above the magnetic source) to maintain this equilibrium. As the superconductor is moved away from the magnetic source, attraction will occur (if the magnetic field is strong enough, you can 'pick up' the non-contacted object).