Hyperfine Interaction and Susceptibility in Some Actinide Metals and Intermetallic Compounds

Abstract

Magnetic effects in a number of actinide metals and intermetallic compounds are being investigated utilizing the 59.6 keV Mössbauer resonance of 237Np in conjunction with bulk susceptibility measurements. The cubic Laves phase compound NpAl2 is found to be ferromagnetic. The paramagnetic moment is 2.30 μB, somewhat lower than in other cubic Np magnetic materials. The saturation magnetic hyperfine field is found to be (3155±50) kOe. Taking H(T)/H(0) = D[1−T/Tc]β, we find D = 1.48±0.10, Tc = 55.8±0.1°K and β = 0.355±0.017 for 0.994>T/Tc>0.83. At lower temperatures, departure from molecular field behavior is seen. In cubic actinide magnetic materials, an electric-quadrupole hyperfine interaction will be observed due to alignment of the unquenched orbital momentum. In NpAl2 we find e2qQ = − (27±1) MHz. For NpC, which has the NaCl structure, we obtain the hyperfine parameters Hi = (4789±50) kOe and e2qQ = (577±58) MHz at 4.2°K. Metallic neptunium (orthorhombic) and americium (hexagonal) show no magnetic hyperfine coupling at temperatures as low as 1.7°K.

Magnetic and electronic properties of the ferromagnetic Kondo-lattice systemNp2PdGa3

“…It turns out that the results of such a fit are not very sensitive to the magnitude of g 0 / g 1 in the range 0.25 ͑singlet-quartet͒-4 ͑quartet-singlet͒. Assuming an arbitrary ratio g 0 / g 1 = 1, we obtain ␥ LT = 123͑1͒ mJ/ K 2 mol Np, ␤ = 0.57͑2͒ mJ/ K 4 mol Np and / k B = 0.44͑2͒ K. Based on the relation B hf =3k B / ͑R 0.5 I N ͒ we obtain B hf = 230͑3͒ T, which corresponds to an ordered magnetic moment M ord = 1.1 B if assuming the relationship between the hyperfine field and the ordered magnetic moment 1 B = 215 T. 18 The observed B hf value for Np 2 PdGa 3 is smaller than those given for cubic NpAl 2 ͑316 T͒ and NpC ͑480 T͒, 19 or hexagonal NpGa 2 ͑525 T͒, 20 but higher than those in tetragonal NpFeGa 5 ͑203 T͒, 21 NpCoGa 5 ͑180 T͒, 22 and NpRhGa 5 ,͑206 T͒ ͑Ref. 23͒ compounds.…”

Moessbauer spectrometry

“…Coulomb excitation recoil implantation into Cr, Fe, Cu, Ge +7A, Tw = 2.25 ± 0.18 X 10-® sec, AR/R = +1 (206,207) Demonstration of effect Alkaline Earths Source 39-h 133Ba absorber / = 0.95% at 4 DyF3-5H20, DyP04 241 Am used as source AE, IS, H vs. T (227) Np(VII) IS (642) M« ~0.01 nm (228) Thorium matrix gives narrower (18) line than oxide AR /R very small (181) Demonstration of effect 7+2 > 0.33 (352) ns tamed by implantation (403, 520, Debye-Waller factors (/) were measured by Singh ef al. (618) for metals and by Mahesh (470) as a function of temperature.…”