P 31 -NMR study of hyperfine interactions and magnetic fluctuations in the neptunium-based filled skutterudite NpFe4 P12

Y. Tokunaga, S. Kambe, H. Sakai, H. Chudo, T. D. Matsuda, Y. Haga, H. Yasuoka, D. Aoki, Y. Homma, Y. Shiokawa, Y. Oonuki

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4 Citations (Scopus)

Abstract

P 31 -NMR measurements have been performed on a single crystal of the neptunium-based filled skutterudite NpFe4 P12. The compound undergoes a ferromagnetic phase transition at TC =23 K. From the field-orientation dependence of the P 31 -NMR line splitting, the angular dependence of the hyperfine interactions between Np5f spin and P 31 nuclear moments has been investigated. We have observed anisotropic transferred hyperfine interactions at the P sites, which lead to an estimate of the local spin density in the P3p orbitals. It is shown that a fraction of the Np5f spin moments is transferred mostly into the P3p orbitals extending toward the inside of a P cage. The weak hybridization between Np5f and P3p orbitals suggests a localized character for Np5f electrons in NpFe4 P12. We have also measured the field and temperature dependences of the nuclear spin-lattice relaxation rate (1/ T1) in several magnetic fields between 18.5 and 78.0 kOe. The 1/ T1 data reveal that the low-energy spin fluctuations of Np5f spin moments are strongly suppressed by applied fields over a relatively wide temperature range up to 4 TC. In this compound, a large and negative magnetoresistance has been known to occur in the same temperature range. The present NMR results demonstrate that the negative magnetoresistance comes from a reduction in the magnetic scattering from Np5f spin moments by an applied field.

Original languageEnglish
Article number054420
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume79
Issue number5
DOIs
Publication statusPublished - 2009 Feb 18

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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