Evidence from NMR of the importance of the hybridization between 5f and conduction electrons in U3Pd20Si6

Maruta, Daisuke; Takagi, Shigeru; Tateiwa, Naoyuki; Kimura, Noriaki; Komatsubara, T.

doi:10.1016/s0921-4526(99)01079-0

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“…Although the localized character of the 5f electrons has been suggested from the observations of the CEF excitations in the inelastic neutron-scattering studies, peak intensities are generally weak compared with rare-earth compounds [165,168]. The overall features of the nuclear spin-lattice relaxation rate 1/T 1 in NMR experiments cannot be interpreted based on the localized mo-ment system for both compounds [169,170], suggesting that the low-energy spin dynamics due to the hybridization between the 5f and conduction electrons. The nature of the localized state of the 5f electrons state may differ from that of the rare-earth 4f electrons systems.…”

Section: Discussionmentioning

confidence: 99%

Itinerant ferromagnetism in actinide 5f -electron systems: Phenomenological analysis with spin fluctuation theory

et al. 2017

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We have carried out an analysis of magnetic data in 69 uranium, 7 neptunium and 4 plutonium ferromagnets with the spin fluctuation theory developed by Takahashi (Y. Takahashi, J. Phys. Soc. Jpn. 55, 3553 (1986)). The basic and spin fluctuation parameters of the actinide ferromagnets are determined and the applicability of the spin fluctuation theory to actinide 5f system has been discussed. Itinerant ferromagnets of the 3d transition metals and their intermetallics follow a generalized Rhodes-Wohlfarth relation between p eff /ps and TC/T0, viz., p eff /ps ∝ (TC/T0) −3/2 . Here, ps, p eff , TC, and T0 are the spontaneous and effective magnetic moments, the Curie temperature and the width of spin fluctuation spectrum in energy space, respectively. The same relation is satisfied for TC/T0 < 1.0 in the actinide ferromagnets. However, the relation is not satisfied in a few ferromagnets with TC/T0 ∼ 1.0 that corresponds to local moment system in the spin fluctuation theory. The deviation from the theoretical relation may be due to several other effects not included in the spin fluctuation theory such as the crystalline electric field effect on the 5f electrons from ligand atoms. The value of the spontaneous magnetic moment ps increases linearly as a function of TC/T0 in the uranium and neptunium ferromagnets below (TC/T0) kink = 0.32 ± 0.02 where a kink structure appears in relation between the two quantities. ps increases more weakly above (TC/T0) kink . A possible interpretation with the TC/T0-dependence of ps is given.PACS numbers: * Phys. Rev. B. 96, 035125 (2017). † Electronic address: tateiwa.naoyuki@jaea.go.jp and conduction states. In actinide metallic compounds, the degree of localization of the 5f electrons differs in different compounds, ranging from strongly localized to itinerant character. The 3d electrons in transition metals also show various degree of localization. Differences between the 5f and 3d electrons are the smaller sensitivity to the crystal field (CF) from ligand atoms and the stronger spin-orbit coupling in the 5f s. The interplay of the spin and the unquenched orbital degrees of freedom gives rise to the peculiar features of the observed physical phenomena in actinide compounds.While many theoretical studies have been done for the role of the 5f electrons on their interesting physical properties [1][2][3], the behavior of the 5f electrons has not been fully elucidated yet. When the 5f electrons have strongly localized character at higher temperature, a Kondo-lattice picture may be appropriate for understanding the formation of the strongly correlated electric states at low temperatures as has been established in the 4f electrons system of the rare-earth cerium (Ce) and ytterbium (Yb) compounds [5][6][7]. Certainly, some actinide compounds show behaviors reminiscent of the Kondo effect such as the logarithmic temperature dependence of the electrical resistivity (ρ ∼ -lnT ). But not all physical properties in actinide compounds have been consis-

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Section: Discussionmentioning

confidence: 99%