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.
Superconducting magnet
The superconducting portions of most current magnets are composed of niobium-titanium. This material has critical temperature of 10 kelvins and can superconduct at up to about 15 teslas. More expensive magnets can be made of niobium-tin (NbSn). These have a "T" of 18 K. When operating at 4.2 K they are able to withstand a much higher magnetic field intensity, up to 25 to 30 teslas. Unfortunately, it is far more difficult to make the required filaments from this material. This is why sometimes a combination of NbSn for the high-field sections and NbTi for the lower-field sections is used. Vanadium-gallium is another material used for the high-field inserts.