Quantum-mechanical ground state of cerous magnesium nitrate

This paper deals with the quantum-mechanical ground state of cerous magnesium nitrate (CMN). The approximation used is that of Luttinger and Tisza and of Niemeijer, in which spin correlations for magnetic ions in the same supercell are taken into account, while those between ions in different supercells are neglected. The method used is that presented in an earlier paper of the present authors. It is found that the quantum-mechanical ground state of CMN is a linear combination of the state with spin orientations those of the classical state found by Niemeijer plus the complementary state. Thus the classical state is a good approximation for quick results. This state has nearly the same energy as the three mutually degenerate states belonging to the ${\overrightarrow{\mathrm{k}}}_1$, ${\overrightarrow{\mathrm{k}}}_2$, and ${\overrightarrow{\mathrm{k}}}_3$ representations of the translation group. These are formed by linear combinations of states with four spins up and four spins down as is the case with the ground state. The results found fit well with the existing experimental information about CMN.