Magnet
Many materials have unpaired electron spins, and the majority of these materials are paramagnetic. When the spins interact with each other in such a way that the spins align spontaneously, the materials are called ferromagnetic (what is often loosely termed as magnetic). Because of the way their regular crystalline atomic structure causes their spins to interact, some metals are ferromagnetic when found in their natural states, as ores. These include iron ore (magnetite or lodestone), cobalt and nickel, as well as the rare earth metals gadolinium and dysprosium (when at a very low temperature). Such naturally occurring ferromagnets were used in the first experiments with magnetism. Technology has since expanded the availability of magnetic materials to include various man-made products, all based, however, on naturally magnetic elements.
Magnetic implant
The magnets used for implantation must be carefully selected and coated in order to successfully implant them. Size is important in this consideration, as too large of a magnet obstructs blood vessels and is likely to reject, or push out of the skin. For this reason, the most common magnet size is a 3×1mm neodymium disk magnet. Usually the magnets used are of the highest strength available, as a stronger magnet leads to higher magnetic field sensitivity. Perhaps the most important consideration is a coating for the magnet, as typical neodymium disk magnets are not suitable for implantation. Magnets must be coated in an inert and biosafe material, so the body does not attack the magnet. Popular magnet coatings include implant grade silicone, titanium nitride, gold and rhodium.
Disc-magnets are implanted with a scalpel, tubes are inserted by syringe. Both is often done without numbing or just ice water (most countries just allow doctors to use numbing).