page_title: Voigt effect
hierarchical_section_title: Voigt effect
caption_attribution_description: English: Schematic of the polar Kerr effect, longitudinal Kerr effect and the Voigt effect
context_page_description: The Voigt effect is a magneto-optical phenomenon which rotates and elliptizes linearly polarised light sent into an optically active medium. Unlike many other magneto-optical effects such as the Kerr or Faraday effect which are linearly proportional to the magnetization, the Voigt effect is proportional to the square of the magnetization and can be seen experimentally at normal incidence. There are several denominations for this effect in the literature: the Cotton–Mouton effect, the Voigt effect, and magnetic-linear birefringence. This last denomination is closer in the physical sense, where the Voigt effect is a magnetic birefringence of the material with an index of refraction parallel and perpendicular to the magnetization vector or to the applied magnetic field.
  For an electromagnetic incident wave linearly polarized and an in-plane polarized sample, the expression of the rotation in reflection geometry is is:
  and in the transmission geometry:
  ,
  where is the difference of refraction indices depending of the Voigt parameter, the material refraction indices and the parameter responsible of the Voigt effect and so proportional to the or in the case of a paramagnetic material.
context_section_description: The Voigt effect is a magneto-optical phenomenon which rotates and elliptizes linearly polarised light sent into an optically active medium. Unlike many other magneto-optical effects such as the Kerr or Faraday effect which are linearly proportional to the magnetization (or to the applied magnetic field for a non magnetized material), the Voigt effect is proportional to the square of the magnetization (or square of the magnetic field) and can be seen experimentally at normal incidence. There are several denominations for this effect in the literature: the Cotton–Mouton effect (in reference to French scientists Aimé Cotton and Henri Mouton), the Voigt effect (in reference to the German scientist Woldemar Voigt), and magnetic-linear birefringence. This last denomination is closer in the physical sense, where the Voigt effect is a magnetic birefringence of the material with an index of refraction parallel () and perpendicular ) to the magnetization vector or to the applied magnetic field.
  For an electromagnetic incident wave linearly polarized  and an in-plane polarized sample  , the expression of the rotation in reflection geometry is  is :
  and in the transmission geometry :
  ,
  where  is the difference of refraction indices depending of the Voigt parameter  (same as for the Kerr effect),  the material refraction indices and  the parameter responsible of the Voigt effect and so proportional to the  or  in the case of a paramagnetic material.
  Detailed calculation and an illustration are given in sections below.
caption: Schematic of the polar Kerr effect, longitudinal Kerr effect and the Voigt effect
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