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Literature Abstracts

 1961.    KÖNIG, H.  [Smallest Ferromagnetic Elementary Size of Iron.]  Naturwissenschaften, vol. 33, 1946, pp. 71-75; Chem. Abs., vol. 41, 1947, p. 7177.

       Review in some detail of history of ferromagnetism and various methods used to determine the size of the elementary Fe magnet.  The author’s method, in which a collodion film with attached Fe layer is brought between the poles of a magnet and the magnetism determined by Farraday effect, rotation of polarized light, is described more specifically.  Differences were found for different types of Fe precipitates.  From 20 different Fe films it was found that the smallest mean crystal size to give measurable rotation; that is, ferromagnetism, is 10-12 Å.  With γ-Fe₂O₃, ferromagnetism does not begin until the particles are 30-40 Å.  In both cases, this indicates the presence of at least 64 elementary cell units.