Investigation on magne-crystallic action VI. Further studies on paramagnetic crystals

Abstract

In some of the earlier papers in this series (Part II, 1933; Part IV, 1936; Part V, 1938) we gave an account of magnetic studies on single crystals of several paramagnetic salts of the rare earth and the iron groups, and a discussion of the results on the basis of the recent theoretical work of Van Vleck (1932a, b), and Penney and Schlapp (1932), on the influence of the strong local electric fields acting on the paramagnetic ions in the crystals on their magnetic behaviour. Paramagnetic studies on single crystals are of interest because of the variety of information one can obtain from them under favourable conditions—on such widely different topics as the magnitude and the asymmetry of the electric field acting on the paramagnetic ion in the crystal; the geometry of distribution of the negatively charged atoms immediately surrounding the paramagnetic ion, and hence the co-ordination number of the ion; the strength of coupling between the orbital and the spin angular momenta of the electrons in the incomplete shell of the ion; and in those crystals in which the paramagnetic ions are all in the S-state, the magnitude of the Stark separation of the S-levels, which plays an important part in determining the thermal properties of the crystal at very low temperatures ( = 0T °K ); etc. Several examples were given, in the papers referred to, to illustrate these various aspects of the magnetic studies on paramagnetic crystals.