Magneto-vortical birefringence in a ferrofluid B. M. Heegaard, J.-C. Bacri, R. Perzynski and M. I. Shliomis Europhys. Lett., 34 4 (1996) 299-304 Published online: 01 September 2002 DOI: 10.1209/epl/i1996-00454-4