Neel, Louis-Eugene-Felix

▪ 2001

      French physicist (b. Nov. 22, 1904, Lyon, France—d. Nov. 17, 2000, Brive-la-Gaillarde, France), shared the 1970 Nobel Prize for Physics for his discoveries concerning new forms of magnetism. His findings led to applications ranging from the development of improved computer memory units to paleomagnetic techniques for establishing the age of fossils. In 1932 he discovered antiferromagnetism, a condition in some solids in which alternating groups of atoms align their electrons in opposite directions, thereby neutralizing the net magnetic effect. In his work on magnetic oxides (known as ferrites in the late 1940s), Néel found that the magnetic fields associated with individual atoms spontaneously align themselves either in the same direction, as in ferromagnetism, or are paired off in opposite directions, as in antiferromagnetism. Consequently, such ferromagnetic materials generally exhibit weaker strength than do the purely ferromagnetic solids, such as metallic iron. Ferrite crystals are essential ingredients in snooper paint, which allows stealth aircraft to be undetectable by radar. Néel served as a professor of science at the University of Strasbourg from 1937 to 1945 and at the University of Grenoble from 1945 to 1976; he was the founder and a former director of the Centre for Nuclear Studies in Grenoble.

* * *

▪ French physicist

born November 22, 1904, Lyon, France

died November 17, 2000, Brive-Corrèze

      French physicist who was corecipient, with the Swedish astrophysicist Hannes Alfvén (Alfvén, Hannes), of the Nobel Prize for Physics in 1970 for his pioneering studies of the magnetic properties of solids. His contributions to solid-state physics have found numerous useful applications, particularly in the development of improved computer memory units.

      Néel attended the École Normale Supérieure in Paris and the University of Strasbourg (Ph.D., 1932), where he studied under Pierre-Ernest Weiss (Weiss, Pierre-Ernest) and first began researching magnetism. He was a professor at the universities of Strasbourg (1937–45) and Grenoble (1945–76), and in 1956 he founded the Center for Nuclear Studies in Grenoble, serving as its director until 1971. Néel also was director (1971–76) of the Polytechnic Institute in Grenoble.

      During the early 1930s Néel studied, on the molecular level, forms of magnetism that differ from ferromagnetism. In ferromagnetism, the most common variety of magnetism, the electrons line up (or spin) in the same direction at low temperatures. He discovered that, in some substances, alternating groups of atoms align their electrons in opposite directions (much as when two identical magnets are placed together with opposite poles aligned), thus neutralizing the net magnetic effect. This magnetic property is called antiferromagnetism. Néel's studies of fine-grain ferromagnetics provided an explanation for the unusual magnetic memory of certain mineral deposits that has provided information on changes in the direction and strength of the Earth's magnetic field.

      Néel wrote more than 200 works on various aspects of magnetism. Mainly because of his contributions, ferromagnetic materials can be manufactured to almost any specifications for technical applications, and a flood of new synthetic ferrite materials has revolutionized microwave electronics.

* * *