While most materials have some magnetic properties, relatively few can be made into magnets. Iron and a few other related metals can easily become magnetized. When alloyed with other metals or made into compounds, they have stronger magnetism or are easier to make. The rare-earth metal neodymium is the basis of the strongest permanent magnets known. Superconducting metals at cryogenic temperatures also make powerful electromagnets.
Iron and related elements, such as cobalt and nickel, belong to a family of ferromagnetic metals. They're naturally attracted to magnets and are easily magnetized.
Ceramic magnets are made of strontium carbonate and iron oxide powder, pressed into forms and polished. Though brittle, they have the advantage of low cost and good magnetic strength.
Getting its name from aluminum, nickel, and cobalt, alnico is an alloy of these and a few other metals. Until rare-earth magnets were developed in the 1980s, these were the strongest permanent magnets known.
These magnets are made from alloys of neodymium. They have the greatest strength of any permanent magnet material, opening up new applications. Tiny, powerful speakers, ear buds, toys and motors use rare-earth magnets.
MRIs use powerful superconducting magnets. These are electromagnets cooled in liquid helium, about 4 Kelvins or minus 269 degrees Celsius. The magnets are wound from niobium-titanium or niobium-tin alloy wire, which loses all electrical resistance at these temperatures.