Magnetic properties of actinide elements having the5f6and5f7electronic configurations

Abstract

Magnetic susceptibility measurements have been made on multimicrogram quantities of ${}_{}{}^{243}{}_{}{}^{}\mathrm{Am}$ ${\mathrm{F}}_3$, ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cm}$ ${\mathrm{F}}_4$, ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cm}$ ${\mathrm{O}}_2$, and ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cm}$Ba${\mathrm{O}}_3$ samples (nominally the $5f^6$ electronic configuration) and on ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cm}_2^{}{}_{}{}^{}$ ${\mathrm{O}}_3$, ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cm}$ ${\mathrm{F}}_3$, ${}_{}{}^{249}{}_{}{}^{}\mathrm{Bk}$ ${\mathrm{F}}_4$, and ${}_{}{}^{249}{}_{}{}^{}\mathrm{Bk}$ ${\mathrm{O}}_2$ (nominally the $5f^7$ electronic configuration) in the temperature range 4.2-300 K and in magnetic fields up to 1650 G. The experimentally determined effective magnetic moments and the Curie-Weiss constants for these compounds are presented. The deviation of the moments for the $5f^6$ compounds from those expected from classic theory is discussed in terms of low-lying excited states, chemical composition, crystal-field perturbations, and realistic electronic structure.