Magnetism
Magnetism is a class of physical phenomena that are mediated by magnetic fields. Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments. The most familiar effects occur in ferromagnetic materials, which are strongly attracted by magnetic fields and can be magnetized to become permanent magnets, producing magnetic fields themselves. Only a few substances are ferromagnetic; the most common ones are iron, nickel and cobalt and their alloys. The prefix "" refers to iron, because permanent magnetism was first observed in lodestone, a form of natural iron ore called magnetite, FeO.
Plastic magnet
In February 2002, researchers from Ohio State University & University of Utah developed the world's first light-tunable plastic magnet.
The plastic material became 1.5 times more magnetic when blue light shines on it. Green laser light reversed the effect somewhat, by decreasing the material's magnetism to 60 percent of its normal level. The plastic magnet was made from a polymer made of tetracyanoethylene (TCNE) combined with manganese (Mn) ions -- atoms of the metal manganese with electrons removed. The magnet functioned up to a temperature of 75 K (about -200ºC, or -325ºF).