Magnetic liquids under high electric fields as optical diodes
  We show and give examples of how unidirectional propagation of light rays in the limit of geometric optics could arise in some magnetic fluids due to the magnetoelectric effect under weak DC magnetic fields and strong DC electric fields around half of their dielectric breakdown. For such liquids as kerosene and transformer oils, one-way propagation of light may occur for 30 nm diameter magnetic nanoparticles (e.g. cobalt) and concentrations of 2% or larger. 
Jonas P. Pereira, Igor I. Smolyaninov, and Vera N. Smolyaninova
physics.optics