Ligand and Actinide NMR Studies in Actinide Oxides and Intermetallic Compounds

Abstract

In this paper we present highlights from a 6-year program of NMR/NQR/AFNMR studies carried out on both actinide and ligand nuclear spins in oxides and intermetallic compounds of the actinide elements U, Np, and Pu. We begin with the large family of actinide 115 compounds, consisting of metallic antiferromagnets, metamagnets, Pauli paramagnets, and the superconducting Pu-based systems. Short summaries are presented of 69;71 Ga NMR studies of the exotic metamagnet NpCoGa 5 , the surprisingly inhomogeneous UCoGa 5 , and the heavy-fermion ''high-T c '' superconductors PuTGa 5 , T ¼ Rh and Co. The case of microdomains in the metallic antiferromagnet UGa 3 is briefly reviewed. Next, we summarize the direct and indirect 235 U NMR studies on USb 2 and URh 3 . These are the first studies of their kind and the only studies of 235 U NMR in a metallic environment. Under the heading of actinide oxides we recap our original studies of 235 U and 17 O NMR in UO 2 , followed by a summary of our investigation of multipolar ordering in NpO 2 via 17 O NMR, in which the 237 Np NMR parameters were determined via cross-relaxation effects. And finally, we summarize our 31 P study of the ferromagnetic transition in the filled Skutterudite UFe 4 P 12 .

17O NMR study in (Pu0.91Am0.09)O2

“…The advantage of NMR experiments is that the static and dynamical electronic properties can be selectively probed for each site in a given compound. In the ordered state of UO 2 , for example, the 17 O NMR has revealed the existence of a large internal field with a tiny electronic field gradient at oxygen sites [1,6,7]. These results have confirmed the transverse triple-q type ordering of magnetic dipoles in UO 2 .…”

“…In order to investigate the electronic state of AnO 2 from a microscopic viewpoint, we have performed a series of nuclear magnetic resonance (NMR) studies using 17 O nuclei [1][2][3][4][5][6][7][8]. The advantage of NMR experiments is that the static and dynamical electronic properties can be selectively probed for each site in a given compound.…”

NMR Study on AmO2: Comparison with UO2and NpO2

“…[16][17][18][19][20][21][22][23][24][25] The longitudinal triple-q Γ 5 antiferrooctupolar (AFO) order scenario was suggested initially by resonant X-ray scattering 17) and then strongly supported from a microscopic viewpoint by 17 O NMR studies. 20,21,[26][27][28] AmO 2 also exhibits a phase transition at T 0 =8.5 K. However, owing to the limited number of experimental data, the mechanism of this phase transition has remained a mystery for more than 30 years. The phase transition was first reported from magnetic susceptibility data, which show a broad max- * E-mail: tokunaga.yo@jaea.go.jp.…”

“…36) In this paper, in order to characterize the magnetic ground states of AmO 2 , we compare our results with those on UO 2 5) and NpO 2 . 20,21,[26][27][28] In Table I, we summarize the crystallographic and electronic properties of the three actinide dioxides. Figure 1 shows the temperature dependence of 17 O NMR spectra.…”

Production and properties of transuranium elements

“…The review paper of Walstedt et al [136] is available for the NMR application to the superconductivity research of actinide alloys and compounds.…”