in the forms needed by society, with a concomitant reduction in cost, fuel requirements, and pollution.
Before about the mid-1930s, the only permanent magnetic materials available were special steels. Modest improvements in the magnetic strength of these materials were made, but significant increases came only with the development of aluminum-nickel-cobalt alloys in the 1940s and 1950s. In the 1960s, the rare earth/cobalt alloys produced the next major jump, and the 1980s saw the development of the neodymium-iron-boron compounds. Today, permanent magnets have magnetic strengths more than 100 times greater than those available at the turn of the century (Figure 1.3). These and other magnetic materials are making possible smaller, more powerful motors and better and smaller sound systems, and they are carrying out many other hidden tasks in modern machines and devices.
Superconductivity was first discovered in 1911. After some 60 years of effort, researchers developed materials suitable for practical use at temperatures up to 23° above absolute zero (23 K, i.e., 250° below 0°C). Then, beginning in 1986, working with entirely new classes of materials, researchers developed a material with a superconducting transition temperature of 39