MAGNETOGYROTROPY IN TWISTED CDS CRYSTALS

In this paper the optical activity (gyrotropy) induced by a simultaneo us action of a magnetic field and a torsion in hexagonal CdS crystals has been investigated. The crystal having undergone to both external i nfluences is placed between two crossed polarizers. The spectral cours e of transmittance of this system near the isotropic point of CdS (the wavelength where the birefringence changes its sign) is studied in th e experiment. An explanation of the experimental results is given by u sing the model of elliptical birefringence in anisotropic gyrotropic c rystals. Taking into account the superposition of both external influe nces, it has been proved that the torsion generates gyrotropy whose pa rameter changes its sign in the isotropic point.