Introductory Chapter

Magnetism is one of the oldest phenomena known to mankind. For example, iron used to be magnetized by stroking it with another magnet or simply by placing it in the proximity of a strong magnet. The oldest magnetic compound, so-called mineral of magnetite (Fe3O4) was initially found in the district of Magnesia of modern Turkey. The word “magnet” is a Greek word. The magnetic properties of materials are entirely governed by the motion of electrons of the atoms. The simplest form of an electromagnet can be produced by wrapping copper wire into the form of a coil and connecting the wire to a battery. A magnetic field is created in the coil, but it remains there only while electricity flows through the wire. There are different types of magnetism existing today. They can be categorized into paramagnetism, ferromagnetism, ferrimagnetism, and antiferromagnetism. The applications of magnetism are many including data storage, magnetic switches, and in the medical field like magnetic resonance imaging (MRI). In 1905, Langevin explained the theory of diamagnetism and paramagnetism but was unable to explain the ferromagnetism. In 1906, the ferromagnetism theory was developed by Weiss. The first commercial steel magnets were made available in 1919 and were quench-hardened steel magnets. In 1930, I. Mishima produced the first Alnico magnet that contained an alloy of iron, aluminum, and nickel. Furthermore, Hermann Kemper studied the use of magnetic fields in conjunction with trains and airplanes. In 1952, J.J. Went et al. invented the first ceramic magnets based on barium, lead-iron oxides, and strontium at the Philips Company. In 1966, rare-earth magnets with high-energy product were reported by Karl J. Stmat. NdFeB magnets have significantly boosted the development of computer peripherals such as voice coil motors and actuators, in both downsizing and enhancing their performance characteristics. For example, in 1984, computer disk drives of ≈10 MB size were in use. Today, external hard drives of much smaller physical dimensions, but with a storage