Switching Faraday rotation on a molecular level

Abstract

In this work we present measurements of the switching of the Faraday effect in metal-organic compounds. Faraday rotation is the rotation of the plane of polarization of linearly polarized light under the influence of a magnetic field in the direction of propagation of the light. It is the magnetic equivalent of circular birefringence and is related to magnetic circular dichroism via the Kramers-Kronig transformation. The Faraday effect is used in optical isolators and magnetic sensors. Faraday rotation and magnetic circular dichroism spectra have been calculated and measured for various nanoparticles, nanocomposites, magnetic fluids and metal-organic complexes. These measurements and calculations indicate that it is possible to change the magneto-optical response by changing the state of the molecule, such as a change in protonation or oxidation state. The molecular environment also influences the magneto-optical spectra of metal-organic complexes and organic molecules. Thus it is possible to change the Faraday rotation spectrum by modifying the molecular environment or the molecule itself. We have measured the reversible switching of the magneto-optical response by these principles. This easily induced reversible switching opens the possibility of new devices such as switchable optical isolators.