Diamagnetism of cadmium

Abstract

The study of the susceptibility of metal crystals has received some attention in recent years both from theoretical and experimental points of view. The careful and thorough investigations of Goetz and Focke (1934) on single crystals of bismuth have greatly extended our knowledge regarding the properties of the crystalline state. McLennan, Ruedy and Cohen (1928) and McLennan and Cohen (1929) have determined the principal suscepti­bilities of a number of metals, including zinc, cadmium, antimony and tin. Hoge (1935) investigated tin crystals and showed the existence of a feeble anisotropy. Rao and Subramaniam (1936) studied thallium and showed from magnetic data the existence of a transformation point (235° C.), at which temperature its ordinary hexagonal structure passes over into the cubic type. Rao (1936 a , b ) has examined the influence of cold-working on single crystals of bismuth, zinc and tin and arrived at important conclusions based on the observed variations of the principal susceptibilities. An extension of this study to other metals and a careful repetition of some of the earlier investigations on the lines of more recent work seem essential. In this paper cadmium has been taken up for special study. We have indeed the values of McLennan and others (1928) for the principal susceptibilities of cadmium, but it is proposed here to study carefully the influence of cold­ working and of foreign matter on its diamagnetism. On the theoretical side a large amount of interesting work has been accomplished. Pauli (1926) applied the Fermi-Dirac statistics to the calculation of the paramagnetism of a free electron gas. If ( χ A ) е is the gram-atomic susceptibility due to the free electrons, q the number of free electrons per atom, and V 0 the width of the occupied energy range in the completely degenerate state in volts, for ordinary temperatures, ( χ A ) e × 10 6 = 48·17( q / V 0 ) {1 ‒ 6·11 × 10 -9 ( T / V 0 ) 2 }. (1)