Cotton–Mouton effect

The Cotton -Mouton effect is a magneto-optical effect. It describes the external by a ( strong ) magnetic field induced optical birefringence in propagation of light perpendicular to the magnetic field direction in normally optically isotropic materials; it is therefore also called magnetic birefringence.

A similar electrical effect is the Kerr effect, in which the strength of the effect also on the strength of the square - dependent field - the electric Kerr effect.

History

The Cotton -Mouton effect in 1907 by Aimé Auguste Cotton and Henri Mouton discovered nitrobenzene and a short time later in other organic liquids demonstrated ( eg, benzene and toluene).

Description

Requirement magnetically polar molecules in the material - they exhibit an electrical and magnetic anisotropy - that the magnetic field experienced by a forced alignment and to conduct the irradiation of light ( generally electromagnetic waves, including microwave, etc.) change. The effect mainly occurs in liquids and is much stronger than the Voigt effect or Majorana effect. It is best with polarized light whose plane of polarization is inclined by 45 ° with respect to the magnetic field observed. In this case, the effect ( the difference between the phase velocity ), the perpendicular or parallel to the magnetic field components of the light lying maximized. The emerging light is elliptically polarized in this case.

The Cotton -Mouton constant which depends on the material, wavelength and temperature, and for example, when nitrobenzene is 3.81 × 10-14 A -2M (at room temperature and a wavelength of λ0 = 589.3 nm). As field strength, however, only the contribution goes perpendicularly to the propagation direction of the light.

Depending on the angle of incidence of the light of the Cotton -Mouton effect is also common with the Faraday effect. It can be used for the optical measurement of the magnetic field strength (such as with particular polarimeter ).