ABSTRACT
Magnetism may be thought of as electricity in motion. It is actually a relativistic effect of moving charges according to Einstein’s special theory of relativity. One observes a magnetic field in a reference frame that electrons are flowing through, but in a reference frame that moves with the electrons, one observes only an electric field. Natural ferromagnets in the form of loadstones were known to the ancient Chinese who used them for navigation. Hans Christian Ørsted was the first person to connect magnetism with electricity when he noticed that a flowing current influenced a compass needle. Magnetic materials continue to play an ever increasing role in our modern technical
society. For example, the recent discovery of low-cost iron-neodymium-boron magnets has made it possible to build highly efficient permanent magnet motors that are used in hybrid vehicles and will be used in future electric vehicles. Another example is the continued development of magnetic storage media, which have extended hard drive storage capacities far beyond what anyone would have expected a decade ago and have made high performance computers affordable to almost everyone. In order to understand how these materials function, we need to start with some basic principles.
