Magnet
Rare earth (lanthanoid) elements have a partially occupied "f" electron shell (which can accommodate up to 14 electrons). The spin of these electrons can be aligned, resulting in very strong magnetic fields, and therefore, these elements are used in compact high-strength magnets where their higher price is not a concern. The most common types of rare-earth magnets are samarium-cobalt and neodymium-iron-boron (NIB) magnets.
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).