Magnetization in Weak Fields as a Function of Frequency

Theory of intensity of magnetization for high frequencies of the impressed field.---The attempt is made to obtain a theoretical explanation of the known variation of the permeability of paramagnetic substances with frequency. The magnetic properties of the atom are supposed due to rings of electrons revolving about a nucleus, the field is supposed weak, and damping is neglected. (1) Paramagnetic solid. A statistical distribution in direction of the axes of the elementary magnets of which a magnetic solid is composed takes place as the result of collisions between molecules. In the time intervening between successive collisions the elementary magnets follow the impressed field, subject to such restraints as are imposed by the molecular field. From these considerations an expression for the permeability is deduced. The permeability is practically independent of frequency at first, then rises to a maximum for a frequency comparable with the number of collisions per unit time, decreases to a value less than one, and finally converges asymptotically to unity for an infinite frequency. (2) Paramagnetic gas. The molecular field is absent, and in consequence there is no maximum in the permeability. After decreasing to a value slightly less than one, the permeability approaches unity asymptotically.