Quick Facts
Born:
November 22, 1904, Lyon, France
Died:
November 17, 2000, Brive-Corrèze (aged 95)
Awards And Honors:
Nobel Prize (1970)

Louis-Eugène-Félix Néel (born November 22, 1904, Lyon, France—died November 17, 2000, Brive-Corrèze) was a French physicist who was corecipient, with the Swedish astrophysicist Hannes Alfvén, 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 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.

Italian-born physicist Dr. Enrico Fermi draws a diagram at a blackboard with mathematical equations. circa 1950.
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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.

This article was most recently revised and updated by Encyclopaedia Britannica.

antiferromagnetism, type of magnetism in solids such as manganese oxide (MnO) in which adjacent ions that behave as tiny magnets (in this case manganese ions, Mn2+) spontaneously align themselves at relatively low temperatures into opposite, or antiparallel, arrangements throughout the material so that it exhibits almost no gross external magnetism. In antiferromagnetic materials, which include certain metals and alloys in addition to some ionic solids, the magnetism from magnetic atoms or ions oriented in one direction is canceled out by the set of magnetic atoms or ions that are aligned in the reverse direction.

This spontaneous antiparallel coupling of atomic magnets is disrupted by heating and disappears entirely above a certain temperature, called the Néel temperature, characteristic of each antiferromagnetic material. (The Néel temperature is named for Louis Néel, French physicist, who in 1936 gave one of the first explanations of antiferromagnetism.) Some antiferromagnetic materials have Néel temperatures at, or even several hundred degrees above, room temperature, but usually these temperatures are lower. The Néel temperature for manganese oxide, for example, is 122 K (−151° C, or −240° F).

Antiferromagnetic solids exhibit special behaviour in an applied magnetic field depending upon the temperature. At very low temperatures, the solid exhibits no response to the external field, because the antiparallel ordering of atomic magnets is rigidly maintained. At higher temperatures, some atoms break free of the orderly arrangement and align with the external field. This alignment and the weak magnetism it produces in the solid reach their peak at the Néel temperature. Above this temperature, thermal agitation progressively prevents alignment of the atoms with the magnetic field, so that the weak magnetism produced in the solid by the alignment of its atoms continuously decreases as temperature is increased.

magnetic field from current loop
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magnetism: Antiferromagnetism