Open AccessII. A contribution to the theory of ferromagnetic crystals
Author(s) -
G. S. Mahajani
Publication year - 1929
Publication title -
philosophical transactions of the royal society of london. series a, containing papers of a mathematical or physical character
Language(s) - English
Resource type - Journals
eISSN - 2053-9258
pISSN - 0264-3952
DOI - 10.1098/rsta.1929.0002
Subject(s) - ferromagnetism , condensed matter physics , symmetry (geometry) , isotropy , theoretical physics , microscopic theory , field (mathematics) , magnetization , physics , magnetic field , mathematics , quantum mechanics , geometry , pure mathematics
This paper aims, in general, at giving an atomistic theory for magnetic phenomena in ferromagnetic crystals. In particular, it explains theoretically Webster’s experimental results with regard to iron crystals. As has been pointed out in the abstract, the fundamental fact of interest in experiments on magnetic substances is that the direction ψ of magnetization I does not in general coincide with the direction φ of the external field H. Experiments on iron crystals have now revealed that this deviation-effect (φ — ψ) exists even in crystals of cubic structure and a symmetrical boundary. In other words, cubical symmetry does not make a body magnetically isotropic, as was erroneously assumed by Faraday, Tyndall and Plücker. To account for this deviation, and in general to relate the two directions ψ, φ, with each other must certainly be the object of any theory bearing on this subject. Accordingly, Weiss developed a macroscopic theory by introducing the conception of the molecular field. This idea served many useful purposes, especially in connection with pyrrhotite. But as is shown in the present paper, it is not adequate to explain the phenomena in the case of crystals with a cubic structure.