Saturation ferromagnetic

Finally, the use of simple valence bond theory has led recently to a significant discovery concerning the nature of metals. Many years ago one of us noticed, based on an analysis of the experimental values of the saturation ferromagnetic moment per atom of the metals of the iron group and their alloys, that for a substance to have metallic properties, 0.72 orbital per atom, the metallic orbital, must be available to permit the unsynchronized resonance that confers metallic properties on a substance.34 38 Using lithium as an example, unsynchronized resonance refers to such structures as follows. 

In order to explain the observed saturation ferromagnetic moment of Fe, 2.22/xb, I assumed that the Fe atom in the metal has two kinds of 3d orbitals 2.22 atomic (contracted) orbitals, and 2.78 bonding 3d orbitals, which can hybridize with 4s and 4p to form bond orbitals. Thus 2.22 of the 8 outer electrons could occupy the atomic orbitals to provide the ferromagnetic moment, with the other 5.78 outer electrons forming 5.78 covalent bonds. 

Fig. 1. Comparison of experimental values (solid curves) and predicted values (dashed lines) of the saturation ferromagnetic moment per atom, in Bohr magnetons, for Fe-Co, Co-Ni, and Ni-Cu alloys. The short vertical lines indicate change in crystal structure (from Ref. (2)).

In 1938 I concluded (2) from the consideration of the values of their saturation ferromagnetic moments that the elements of the first transition sequence from Cr to Ni have the constant metallic valence 5.78, later revised 8) to 6. Despite their lack of ferromagnetism, I assumed (9) in 1947 that their heavier congeners Mo to Pd and W to... 

It should be emphasized that the derivation of w given here is completely theoretical, and as far as can be determined, the conventional band theory has never been employed to predict the composition Ni44Cu56 at which the saturation ferromagnetic moment of the first-row transition metal alloys has the value zero. 

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