On the Toroidal Arrangement of the 180° Domain Walls in Ring Polycrystalline Soft Ferrites P. Le Fur, A.M. Konn, F. Liorzou et M. Le Floc'h J. Phys. IV France, 07 C1 (1997) C1-199-C1-200 DOI: 10.1051/jp4:1997174