Magnetic state of f electrons in δ-phase of Pu–Ga alloys studied by Ga NMR

The influence of defects on magnetic properties of fcc-Pu

“…The implementation of the LDA + DMFT method is necessary for a more accurate description of the magnitudes of local moments in the paramagnetic phase of Pu. The results of calculations explain the presence of magnetic moment in aged Pu samples and agree well with experimental data [6,11,12]. …”

“…Impurities like Al and Ga that are used to stabilize the fcc phase of Pu act in the same way. Several groups report the presence of the ordered magnetic moment in aged Pu-Al and Pu-Ga alloys [10][11][12]. The magnitude of moments is small, ≤10 -3 μ B ( [10])-0.15 μ B ( [11,12]), and these moments could arise due to distortion of the crystal structure near interstitial Pu atoms and vacancies.…”

69Ga NMR and magnetic susceptibility in δ-phase of Pu1−xGax (x=0.05, x=0.08) alloys

“…It was shown [4][5][6]9] that NMR line shift (K) and the nuclear spin-lattice relaxation rate (T 1 ) À1 of Ga are determined by local magnetic field that arise at the NMR probe nucleus due to the spin polarization transferred from the f-electron shells of the actinide neighbor. Thus, the temperature variation of the gallium NMR line shift K traces thermal behavior of the spin contribution v s to the magnetic susceptibility.…”

“…Unusual properties of plutonium and its alloys come from the dominant role of its narrow 5f band. The large electron contribution to the specific heat [2], the high resistivity q(T), and its nonmonotonic temperature dependence with a maximum below 200 K [3], abnormal temperature dependence of the static spin susceptibility, v s , displayed by 69 Ga nuclear magnetic resonance (NMR) shift [4][5][6], magnetic instability, arisen due to self-damage in d-Pu alloy at low temperature [7] are the characteristic macroproperties of d-Pu that make this material close to heavy-fermion systems with a strong localization of f-electrons [8]. At the same time a general conclusion of many experimental researches of a Pu-Ga alloy magnetic state is the following: electronic correlations in d-Pu are of a dynamic character and their evolution never ends in static magnetic order at low T.…”

“…3). It was cleared up before [4,6] that NSLR in Ga05 was determined by time-dependent local field at the Ga sites created by spin fluctuations of the f-electrons via the RKKY interaction rather than the Fermi-contact interaction of nuclear spin with conducting electrons (Korringa contribution). Furthermore, the temperature dependence of the value (T 1 T) À1 at T > 100 K is close to the power-law curve ðT 1 TÞ À1 / ðT þ h T 1 Þ À1:5 observed in 3D nonmagnetic Kondo lattice, where the localized electron spins fluctuate without any macroscopic coherence and keeping themselves only the short-range spin correlations with x sf $ T 0.5 [12].…”