Something is a magnet when it creates its own magnetic field strong enough to noticeably attract or repel other magnets or certain metals. This comes from how the electrons inside the material are arranged and aligned.
Atoms and tiny magnets
Each atom has electrons that behave like tiny bar magnets because of their motion and an intrinsic property called spin. In most materials, these tiny magnets point in random directions, so their effects cancel and the object is not magnetic overall.
Magnetic domains
In ferromagnetic materials such as iron, cobalt, and nickel, groups of atoms line up so their tiny magnets point the same way, forming regions called magnetic domains. If the domains are randomly oriented, the material shows little or no net magnetism, but if many domains line up in one direction, the whole piece acts as a magnet.
How something becomes a magnet
A piece of suitable material becomes a magnet when an external magnetic field or electric current forces many of its domains to align. This can be done, for example, by putting the material in a strong magnetic field, by running current through coils around it (electromagnets), or by repeatedly stroking it with an existing magnet.
Permanent vs temporary magnets
“Hard” magnetic materials keep most of their domains aligned even after the external field is removed, so they become permanent magnets. “Soft” magnetic materials lose that alignment easily, so they are only magnetic while a field or current is present and are used where controllable, temporary magnetism is needed.
