Relaxation anomalies of 69/71Ga NQR in the paramagnetic state of the itinerant antiferromagnet UGa3: Possible evidence for a crossover to localized spin fluctuations and development of orbital fluctuations of 5f-electrons at high temperatures

Shigeru Takagi, Hideaki Muraoka, Tatsuma D. Matsuda, Yoshinori Haga, Shinsaku Kambe, Russell E. Walstedt, Etsuji Yamamoto, Yoshichika Onuki

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Abstract

The microscopic magnetic properties of the itinerant 5f-electron antiferromagnet UGa3 (TN = 67 K) have been investigated in the paramagnetic state by means of Ga NQR studies of the two naturally abundant isotopes 69Ga and 71Ga. A striking and unusual increase of the nuclear longitudinal relaxation rate 1/T1 has been observed above 230 K, which includes a strong component of nuclear quadrupolar relaxation. Both the magnetic and quadrupolar relaxation rates have been found to increase simultaneously above 230 K. Correspondingly, the NQR frequencies also show a clear deviation from lower-T T3/2-dependence above 230 K. These results are discussed in terms of a crossover from lower-T itinerant to higher-T more localized spin fluctuations and associated orbital fluctuations on the part of the U 5f electrons. A mechanism of transferred quadrupole interaction is presented, through which the fluctuations among the U 5f orbitals involve those among the counter-anion Ga 4p orbitals and thereby cause quadrupolar relaxation of the Ga nuclear spins.

Original languageEnglish
Pages (from-to)469-474
Number of pages6
Journaljournal of the physical society of japan
Volume73
Issue number2
DOIs
Publication statusPublished - 2004 Feb 1

Keywords

  • Ga NQR
  • Itinerant↔localized crossover
  • Orbital fluctuations
  • Transferred quadrupole interaction
  • U compounds
  • UGa

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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