214.    BERTAUT, F.  [Coercive Force and Crystallite Size.]  Compt. Rend., vol. 229, 1949, pp. 417-419.

                   Coercive force of Fe powders prepared at different temperatures by H₂ reduction of the formate show marked peak (~1,000 gauss) for size, about 200 Å.  This is generally in accord with Néel’s views on shape anisotropy and the results suggest a critical size below which the Fe crystallites behave paramagnetically, but traces of Fe₂O₃ may complicate the interpretation.