Because of a quantum property called spin, electrons attached to those chains act like tiny bar magnets. (newscientist.com)
To be magnetic a molecule has to have isolated electrons, which act like tiny bar magnets. (scientificamerican.com)
The nanoclusters — about 20,000 per square micrometer — act like tiny bar magnets with «spins» that can be oriented either randomly or in a coordinated manner. (sciencedaily.com)