1. Previous notice of this research has been given inNuovo Cimento,6, 242 (1957).
2. C. Macmillan:Gen. El. Rev.,39, 225 (1936);I. Kunz:Phys. Zeits.,13, 591 (1912);M. S. Procopin:Comft. Rend.,228, 457 (1949).
3. F. Peeisach:Zeits. f. Phys.,94, 277 (1935). See alsoBecker undDöring:Ferromagnetismus (1939), p. 221.
4. L. Néel:Cahier de Physique, No. 12 (1942).
5. L. Llibutey:Thèses 17, Univ. de Grenoble (1950).