Magnetism
Magnetism is a class of physical phenomena that are mediated by magnetic fields. Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments. The most familiar effects occur in ferromagnetic materials, which are strongly attracted by magnetic fields and can be magnetized to become permanent magnets, producing magnetic fields themselves. Only a few substances are ferromagnetic; the most common ones are iron, nickel and cobalt and their alloys. The prefix "" refers to iron, because permanent magnetism was first observed in lodestone, a form of natural iron ore called magnetite, FeO.
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).