Paul Langevin

	Paul Langevin (1872 – 1946) was one of the fathers of magnetism.
		In the "miracle year" 1905, when Einstein published three revolutionary papers, Langevin published his theory of para- and diamagnetism.
		Considering that quantum theory had yet to be discovered, and that statitical thermodynamics was in its infancy, his contribution was of amazing insight.
		As far as paramgnetism was concerned, he first established the treatment we used in the text for orientaiio polarization (which is formally indenticl to paramagnetism).
	The resulting function of the form L(a) = –1/a + coth(a) is therfore called teh Langevin functions (or sometime Langevin-Debye function, since Debye used the same procedure somerwhat later for polar molecules).
	Langevin also worked in the field of Brownian motion (like Einstein). His work concerning ultrasonic sound during world war I was the base for sonar technology .

With frame

3.2.4 Orientation Polarization

© H. Föll (Advanced Materials B, part 1 - script)