Magnetic properties of actinide elements having the5f6and5f7electronic

Abstract

Magnetic susceptibility measurements have been made on multimicrogram quantities of AmF3, '4'CmF4, "'CmO2, and ' 'CmBa03 samples (nominally the 5f electronic configuration) and on ' 'CmzO&, '"'CmF3, ' BkF"and ' BkOz (nominally the 5f' 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-gneiss constants for these compounds are presented. The deviation of the moments for the 5f 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.

Nature of the5fstates in actinide metals

“…Examining Fig. 18(a), (b), and (c) together clearly shows that if the intermediate coupling curve remained near the jj limit for Cm, the spin (and total) magnetic moment would be much smaller than the observed ~8 μ B /atom magnetic moment (Marei and Cunningham, 1972;Huray et al, 1980;Nave et al, 1983;Huray and Nave, 1987) and have little or no effect on the crystal structure of the metal.…”

“…This creates a strong spin polarization though Hund's rule, producing an effective magnetic moment of ~8 μ B /atom in Cm metal (Marei and Cunningham, 1972;Huray et al, 1980;Nave et al, 1983;Huray and Nave, 1987). Pu, Am, and Cm all exhibit intermediate coupling; however, while Pu and Am exhibit strong spin-orbit interactions, Cm is strongly shifted towards the LS limit.…”

Electronic structure and ionicity of actinide oxides from first principles

“…[60] It has been shown that, for a range of off-stoichiometric compounds CmO 2−x , both the lattice parameter and magnetic moment increase with x. [61,62,63] Given the expected moments of Cm 3+ (5f 7 ; µ ef f =7.94 µ B ) and Cm 4+ (5f 6 ; µ ef f =0 µ B ) it was noted that this trend indicates an increase in the number of Cm 3+ impurities as we move away from stoichiometry. Based on the ionic picture, one accordingly expects the Cm 4+ ground state configuration for the stoichiometric compound, which however seems to be contradicted by the fact that in samples very close to stoichimetry, [64] susceptibility measurements give the effective moment as high as µ ef f = 3.36 µ B .…”

Thermodynamic Systematics of Oxides of Americium, Curium, and Neighboring Elements

“…Although the perovskites BaMOa are significantly more stable than the binary oxides (43), the perovskite BaCmO3 still showed significant Cm(III) from magnetic measurements (27). Quantitative results on the enthalpy of stabilization of numerous uranium, neptunium, and most recently plutoniura complex oxides should guide efforts to synthesize new complex oxides of Am and Cm (44,45).…”

“…Despite the more recent availability of 2 **^Cm, which appeared from thermogravimetric measurements and X-ray powder diffraction lattice parameter to yield stoichiometric CmO2.00 in oxygen at 1 atm pressure, recent magnetic susceptibility determinations infer significant hypostoichiometry (x near 0.2 in CmO 2 _ ) (24)(25)(26)(27). Very careful annealing in pure oxygen for several days at 1 atm pressure and even at 100 atm pressure (25,26) failed to eliminate Curie-Weiss paramagnetism attributable to Cra(III).…”