Neel (Neel), Louis( French physicist, Nobel Prize in Physics, 1970)
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Biography Neel (Neel), Louis
genus. November 22, 1904
French physicist Louis Eugene Felix Neel was born in Lyon in the family of Louis Neel, director of one of the civil service, and Marie Antoinette (nee Hartmayer) Neel. After LycцLe du Park, Lyon and LycцLe Saint-Louis in Paris, he entered the prestigious Ecole normal syuperer, which culminated in 1928. began working there as a lecturer. Then he began postgraduate studies at the University of Strasbourg under the leadership of Pierre Weiss, received in 1932. doctorate.
Weiss, as Pierre Curie, one of the first to begin research in the theory of magnetization (magnetic properties, which substance becomes an external magnetic field). Although he managed to give a quantitative explanation of many experimental facts, he could not, however, accurately explain the interaction of two neighboring elementary magnets (ie. neighboring atoms, which behave like little magnets). In 1928, when H. began to study the magnetization, Werner Heisenberg successfully explained this interaction by means of articulated shortly before the quantum theory.
. By this time, were known to three types of magnetic materials: Diamagnetism, paramagnet and ferromagnets
. In diamagnets, . such, . as bismuth and antimony (which are slightly repelled by an external magnetic field), . and paramagnetic, . such, . as aluminum and platinum (which are slightly attracted to the external field), . elementary magnets is largely independent of each other,
. Consequently, the magnetic fields in these materials are oriented in different directions, so that they almost cancel each other. In ferromagnetic substances, such as iron and nickel, the neighboring atoms interact in such a way that their magnetic fields tend to orient in the same direction. Heisenberg was able to show that such interaction leads to the macrocharacteristics, which manifest themselves in a real ferromagnetic substances.
Based on the work of Heisenberg, H. hypothesized that some substances in the interaction of neighboring atoms, their magnetic fields oriented in opposite directions. He suggested that the crystal lattice of such substances can be regarded as two independent interpenetrating sublattices, each of which consists of atoms with identically oriented magnetic fields. This rigid orientation leads to the fact that below a certain temperature, now known as the Neel point, the fields cancel each other out, giving zero magnetization. However, above the NцLel point begin to show the effects of paramagnetic. Examples of substances likely to have similar properties (now they are called antiferromagnets), were discovered in 1937, but only in 1949. Neel theory to validate the study of neutron diffraction.
In 1937, Mr.. N. was appointed professor of Faculty of Science, University of Strasbourg and remained in that post until 1945,. After the Second World War he served orders governance French naval forces in dealing with the protection of warships from magnetic mines. At the end of the war, in 1945, he enrolled at the University of Grenoble, where he founded the Laboratory of Metal Physics and electrostatics, which even led to the 1976
Three years after the transition in Grenoble H. speculated about the existence of another form of magnetization, which he called ferrimagnetizmom. It has long been known that the ferrite - a class of minerals, which includes magnetite (magnetite), - exhibit anomalous behavior in comparison with the ferromagnetic substances, though they belong to one class. Assuming that the ferrite formed a separate class, H. summarized his early theory of antiferromagnetism to explain the behavior ferrimagnetizma. In ferromagnetic substances, he argued, the magnetic fields of the two arrays have different values, so that the resultant magnetic effect is manifested. Some of these substances, including magnetite, have not two, but three bars, two of which cancel each other.
. Ferrites that are not electrical conductors, have since used as a cover tape, in computer memory devices, in communication engineering and in many other areas
. Production for this purpose artificial ferrites based largely on the discoveries N.
In 1956, Mr.. N. invited to create and lead the Center for Nuclear Studies in Grenoble, where he studied neutron diffraction and crystal growth. He also participated in the creation of a Franco-Germanic reactor with a high flux density in Grenoble. To a large extent due to the role that H. played in the scientific life of Grenoble, this city became the largest center of physical research.
. Among the problems, . dealt N., . - Study of the magnetic aftereffect (changes, . occurring with ferromagnetism in time), . study the properties of very fine-grained ferromagnetic substances, . Develop methods for improving the magnetic properties of substances,
. His work on paleomagnetism, which helped to explain the 'magnetic memory' of rocks in the process of change in Earth's magnetic field, a decisive contribution to confirmation of the theory of continental drift and the theory of tectonic plates.
H. received in 1970. Nobel Prize in Physics "for fundamental work and discoveries concerning antiferromagnetism and ferrimagnetizma, which resulted in important applications in solid state physics'. He shared the award with Hannes Alfvenom, which in turn was rewarded for his work on magnetohydrodynamics. When presenting the laureate Torsten Gustafsson, Member of the Royal Swedish Academy of Sciences, said that 'important effects in solid state physics have found their own explanation' in the theories of reward.
In 1931, Mr.. N. married Ellen Urtik, they have one son and two daughters. He likes to take long walks, reading French literature in the XVIII. and mysterious stories, as well as carpentry.
In addition to the Nobel Prize, H. was awarded Holveka Physical Society of London (1952) and the gold medal of the National Center for Scientific Research in Paris. He has many honorary degrees and is a member of the French Academy of Sciences, the American Academy of Arts and Sciences, Academy of Sciences, Royal Society of London and the scientific academies of many other countries. From 1963 to 1983. N. was the representative of France in the NATO Science Committee, and from 1963 to 1965. served as President of the International Union of Pure and Applied Physics. Since 1981, Mr.. he - president of the Supreme Council for Nuclear Safety. In 1966, Mr.. He became a knight of the French Legion of Honor