On the Theory of Diamagnetism

Abstract

Relations between the Weber-Langevin theory and that of Pauli. The first theory gives a band for the Zeeman effect; the second, which is based on Larmor precession, gives sharp lines, as is known. The susceptibilities, K1 and K2, are different except when the orbits are normal to the intensity H of the magnetic field. When they are parallel to H, K1 vanishes and K2 is half that for the normal orbits, an extreme case. In the simplest case, viz., that of coplanar orbits, the ratio of the susceptibility KR for random orientation of the orbits to that KP for similar orientation with all orbital axes parallel to H is 1/3 by the first theory, and 2/3 by the second. In the general case of Pauli's theory KR / KP=2 / 3×(ratio of total ''quadrupolmoment'' to quadrupolmoment normal toA), where A designates a principal atomic axis, which may be normal to no orbit, and KP the susceptibility when A is parallel to H. In the general case of random orientation K2 / K1=2. Molecular magnetic orientation. In 1910 Langevin showed that the magnetic field tends to orient unsymmetrical diamagnetic atoms, so as to make the magnitude of the extraneous flux through the orbits a minimum. The general law is similar to that for magnetic double-refraction, alignment approaching completeness and diamagnetic susceptibility approaching a minimum as H increases and temperature decreases. Thus this theory cannot explain the recent results of Glaser on the variation of susceptibility with pressure; it is suggested that these may possibly be due to a quantization resulting from the weak magnetic moment produced according to either theory in an intense field. Larmor precession of a diamagnetic atom is shown to be independent of orbital motions and due to the same cause as Weber's rotations.

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