Final answer:
A magnet is a material that attracts iron and iron-containing materials. Ferromagnetic materials such as iron, cobalt, nickel, and gadolinium can be magnetized to become permanent magnets, which retain magnetic properties without an external field.
Step-by-step explanation:
A magnet is any material that attracts iron and materials that contain iron.
Materials like iron, cobalt, nickel, and gadolinium are ferromagnetic. These are not just attracted to magnets, but they can also be magnetized themselves; meaning they can be turned into permanent magnets. Permanent magnets are those which retain their magnetic properties for a long time even when external magnetic fields are removed. The process of magnetization aligns the domains, which are millimeter-sized regions where the atoms act like small magnets because of currents within the atoms.
Ferromagnets like neodymium, made from the alloys of rare earth elements, are strong and permanent magnets utilized in various applications. They exhibit spontaneous magnetisation, indicating a self-generated magnetic field without the need for an external cause.