<Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> A magnet is a material or object that produces a magnetic field . This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, and attracts or repels other magnets . </P> <P> A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field . An everyday example is a refrigerator magnet used to hold notes on a refrigerator door . Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are called ferromagnetic (or ferrimagnetic). These include iron, nickel, cobalt, some alloys of rare - earth metals, and some naturally occurring minerals such as lodestone . Although ferromagnetic (and ferrimagnetic) materials are the only ones attracted to a magnet strongly enough to be commonly considered magnetic, all other substances respond weakly to a magnetic field, by one of several other types of magnetism . </P> <P> Ferromagnetic materials can be divided into magnetically "soft" materials like annealed iron, which can be magnetized but do not tend to stay magnetized, and magnetically "hard" materials, which do . Permanent magnets are made from "hard" ferromagnetic materials such as alnico and ferrite that are subjected to special processing in a strong magnetic field during manufacture to align their internal microcrystalline structure, making them very hard to demagnetize . To demagnetize a saturated magnet, a certain magnetic field must be applied, and this threshold depends on coercivity of the respective material . "Hard" materials have high coercivity, whereas "soft" materials have low coercivity . The overall strength of a magnet is measured by its magnetic moment or, alternatively, the total magnetic flux it produces . The local strength of magnetism in a material is measured by its magnetization . </P>

A permanent magnet is a magnet made from a material that