Observation of the inverse Cotton-Mouton effect

Abstract

-We report the observation of the Inverse Cotton-Mouton Effect (ICME) i.e. a magnetization induced in a medium by non resonant linearly polarized light propagating in the presence of a transverse magnetic field. We present a detailed study of the ICME in a TGG crystal showing the dependence of the measured effect on the light intensity, the optical polarization, and on the external magnetic field. We derive a relation between the Cotton-Mouton and Inverse CottonMouton effects that is roughly in agreement with existing experimental data. Our results open the way to applications of the ICME in optical devices.The Inverse Cotton-Mouton Effect (ICME) is a magnetization induced in any medium by a non resonant linearly polarized light beam propagating in the presence of a transverse magnetic field. This magnetization is proportional to the value of the magnetic field, and to the intensity of the propagating electromagnetic waves (see ref.[1] and refs. therein). The ICME was predicted for atomic and molecular systems [2] and for the quantum vacuum [3]. As stated in ref.[1], microscopically, the light-induced dc magnetization arises because the optical field shifts the different magnetic states of the ground manifold differently, and mixes into these ground states different amount of excited states.As shown in ref.[3] the ICME is related to the term in the expansion of the electromagnetic energy of the medium U which is quadratic in the electric and in the magnetic field, which can be written as:where ǫ 0 is the vacuum permittivity, µ 0 the vacuum permeability, χ αβγδ is the second order magnetic and electric susceptibility, f α , f β the local electric field factors, E the electric field and B the magnetic field. Einstein summation is assumed and ( α, β, γ, δ) = x, y, z. Assuming Kleinman symmetry [1], the medium magnetization can be finally calculated using the relation M = − ∂U ∂B .

Theory of spin and lattice wave dynamics excited by focused laser pulses

“…Our model takes into account all dipolar-exchange spin wave modes. The model can be extended to include magneto-optical and transient demagnetization torques generated by an ultrafast-laser pulse [7,9,13] by inverting our equation (10), although the present experiments analyzed here do not provide unequivocal evidence for their existence. Very recently, Hashimoto et al [31] interpreted the spatiotemporal distribution of the laser-induced magnetization dynamics in terms of the magnetic fields induced by demagnetization of the laser hot spot.…”

“…Next we derive the driving field H T in equation (10). In the long-wavelength limit, the magnetoelastic coupling energy [22,23] in our configuration reads…”

“…Generation, manipulation, and detection of spin polarization by ultrafast laser pulses are powerful techniques in the field of spintronics and magnetism [1][2][3][4][5]. Such operations rely on laser pulse-induced demagnetization due to heating [6], the change of magnetic anisotropy due to charge transfer [1,2], magnetooptical (inverse) Faraday effect (IFE) [7][8][9], and (inverse) the Cotton-Mouton effect [10]. Recent experiments demonstrated magnetoelastic coupling of coherent acoustic sound waves generated by the local heating caused by optical gratings [11,12] and laser spots [13][14][15][16] with spin waves.…”

Magnetic and electric properties of a quantum vacuum

“…The observation of the ICME has only been reported very recently in a Terbium Gallium Garnet crystal [125]. The ICME has also been calculated for the quantum vacuum in ref.…”

Inverse transverse magneto-optical Kerr effect

“…It is not the only Faraday effect which was shown to have its inverse counterpart. Thus, the inverse Cotton-Mouton effect was observed recently in terbium gallium garnet crystal [8]. Due to this effect, the medium magnetization is induced in a medium by a linearly polarized light propagating in the presence of a transverse magnetic field.…”