Theory of Some Magnetic Properties of Cobalt Tutton Salts

Abstract

The g-values in the paramagnetic resonance experiment and the static ma~netic susceptibilities of the cobalt Tutton salts are calculated under the assumption that the crystalline field is nearly cubic with a small tetragonal component. The values of these quantities depend on the value of a parameter 71 = 4lJ /3}., where lJ is the energy separation between the lowest energy levels when the spin-orbit coupling is disregarded, and }. is the spin-orbit coupling constant. Comparing the theoretical results with the experimental data, we have estimated 71=3.5--4.5 from g-values, 7J=4~5 from 2.L but the measured values of 211 do not faU between the theoretical curves of 211 versus T with 71=4 and 5. This dis­ crepancy is discussed. The behaviour of the paramagnetic ion in the magnetically dilute crystal can be many experimental methods. One of the most direct method is the paramagnetic resonance experiment. The measurement of the static magnetic susceptibility offers also a powerful but somewhat indirect means for the purpose. Making some reasonable assumptions on the symmetry and magnitude of the electrostatic field acting on the paramagnetic ion in the crystal, we can calculate theoretically the energy levels of the ion, the g-values and its static magnetic susceptibility. If the experimental values of those quantities can be explained consistently by the adjustment of some parameters appearing in the theoretical calculation, the theory will be warranted. We performed this type of calculation for the Cobalt Tutton salt, since the experimental data are available in this case.