Pierre Weiss
Encyclopedia
Pierre-Ernest Weiss was a French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...

 who developed the domain theory of ferromagnetism
Domain theory of ferromagnetism
Domain theory of ferromagnetism explains two significant observations of materials such as iron:#The material may become strongly magnetized by application of a weak external magnetizing field....

 in 1907. Weiss domains and the Weiss magneton
Weiss magneton
The Weiss magneton was an experimentally derived unit of magnetic moment equal to joules per tesla, which is about 20% of the Bohr magneton. It was suggested in 1911 by Pierre Weiss.-Origin:...

 are named after him. Weiss also developed the Molecular or Mean field theory
Mean field theory
Mean field theory is a method to analyse physical systems with multiple bodies. A many-body system with interactions is generally very difficult to solve exactly, except for extremely simple cases . The n-body system is replaced by a 1-body problem with a chosen good external field...

, which is often called Weiss-mean-field theory.

Weiss was born in Mulhouse
Mulhouse
Mulhouse |mill]] hamlet) is a city and commune in eastern France, close to the Swiss and German borders. With a population of 110,514 and 278,206 inhabitants in the metropolitan area in 2006, it is the largest city in the Haut-Rhin département, and the second largest in the Alsace region after...

 and died in Lyon
Lyon
Lyon , is a city in east-central France in the Rhône-Alpes region, situated between Paris and Marseille. Lyon is located at from Paris, from Marseille, from Geneva, from Turin, and from Barcelona. The residents of the city are called Lyonnais....

.
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