Static magneto-optical birefringence of size-sorted γ-Fe2O3 nanoparticles E. Hasmonay, E. Dubois, J.-C. Bacri, R. Perzynski, Yu. L. Raikher and V. I. Stepanov Eur. Phys. J. B, 5 4 (1998) 859-867 Published online: 15 October 1998 DOI: 10.1007/s100510050512