Magnetic anisotropies and the valencies of paramagnetic atoms in crystals

Abstract

Studies on the magnetic anisotropies of paramagnetic crystals are of interest because of the variety of information one can obtain from them under favourable conditions, on such widely different topics as (1) the magnitude and the asymmetry of the internal electric field acting on the paramagnetic ion in the crystal ; (2) the geometry of distribution of the negatively charged atoms immediately surrounding the paramagnetic ion, and hence the co-ordination number of the ion ; (3) the magnitude of the Stark-separation of the energy levels of the ion in the above field (in the special case when the paramagnetic ion in the crystal is in the S-state, the Stark-separation of its levels is naturally feeble, and it plays an important part in determining the thermal behaviour of the crystal at very low temperatures, in the neighbourhood of 0.1° K.) ; (4) the strength of coupling between the orbital and the spin angular momenta of the electrons in the incomplete shell of the ion, etc. In some recent papers we have dealt with these various aspects of paramagnetic studies on single crystals. In the present note We wish to direct attention to another useful application, namely, to questions concerning the valency of the paramagnetic atom in the crystal.