Fundamentals of Magnetism

Magnets play a crucial role in a modern life; as we know, a vast number of devices are employed in the electromagnetic industry. In ancient times human beings experienced magnetic phenomena by utilizing natural iron minerals, especially magnetite. It was not until modern times that magnetic phenomena were appreciated from the standpoint of electromagnetics, to which many physicists such as Oersted and Faraday made a great contribution. In particular, Amp è re explained magnetic materials in 1822, based on a small circular electric current. This was the fi rst explanation of a molecular magnet. Furthermore, Amp è re ’ s circuital law introduced the concept of a magnetic moment or magnetic dipoles, similar to electric dipoles. Macroscopic electromagnetic phenomena are depicted in Figure 1.1 , in which a bar magnet and a circuital current in a wire are physically equivalent. Microscopic similarity is shown in Figure 1.2 , in which a magnetic moment or dipole and a microscopic electron rotational motion are comparable but not 1