Status of understanding of the hybridization-mediated anisotropic magnetic behavior of PuSb

In our previous work a successful theory was developed, on the basis of hybridization-mediated anisotropic interactions, for the unusual magnetic properties of PuSb. The phase transitions and variation of ordered moment size with temperature for PuSb were explained. Calculated energies and dispersion shapes of magnetic excitations from that theory agree very well with subsequent experiments. However, there are remaining significant discrepancies between theory and experiment for the excitation behavior, and these are addressed in the present paper. Motivation for, and consequences of, including a weak quadrupole interaction are presented. Inadequacies of our earlier approximation for the intermediate-coupled ground state of ${\mathrm{Pu}}^{3+}$(${\mathrm{f}}^5$) are discussed, and the need to use the exact intermediate-coupled ground state is demonstrated. We also discuss the choice of selection rule used to pick out the scattering processes used to calculate the scattering amplitudes which determine the angular dependence of the anisotropic interaction between a pair of ${\mathrm{Pu}}^{3+}$ ions.