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Study of the positive muon Knight shift in \(\): Evidence for a tetravalent \(\)-state and crystalline electric field splitting

  • A. Schenck
  • N.K. Sato
  • G. Solt
  • D. Andreica
  • F.N. Gygax
  • M. Pinkpank
  • A. Amato

Abstract:

We report on transverse field (TF) Muon Spin Rotation (μSR) measurements on a single crystal of the hexagonal heavy fermion superconductor UNi2Al3 between 5 K and 300 K. From the measured muon \(\) Knight shift (KS) in the easy (a,b)-plane and along the c-axis we extracted the local magnetic susceptibility tensor [0pt] \(\), which arises from the nearest U-neighbors. By comparison with the bulk susceptibility [0pt] \(\) it is found that [0pt] \(\) and [0pt] \(\) agree well above 150 K but deviate considerably in the basal plane below 150 K, due to the disturbance introduced by the \(\). We succeed in reproducing both [0pt] \(\) and [0pt] \(\) on the basis of a crystalline electric field (CEF)-approach assuming U to be in the tetravalent \(\) state. The disturbance introduced by the \(\) affects the CEF-Hamiltonian in an expected manner, suggesting strongly that a CEF-picture implying a rather local 5f-electron wave function is indeed valid. Reanalyzing older data on UPd2Al3 we arrive at the same conclusion. A necessary condition for extracting the local susceptibility was the knowledge of the \(\)-site, this information was derived from the analysis of the TF-relaxation rates. At low temperatures we found about 30% of the implanted \(\) at the d-site and none at this site above 200 K. The majority fraction was found to be in a tunneling state over six m (or k)-sites around the b-site. No long range diffusion was seen up to room temperature.

PACS. 76.60.Cq Chemical and Knight shifts[:AND:] 71.70.Ch Crystal and ligand fields - 76.75.+i Muon spin rotation and relaxation 

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Copyright information

© EDP Sciences, Springer-Verlag, Società Italiana di Fisica 2000

Authors and Affiliations

  • A. Schenck
    • 1
  • N.K. Sato
    • 2
  • G. Solt
    • 3
  • D. Andreica
    • 1
  • F.N. Gygax
    • 1
  • M. Pinkpank
    • 1
  • A. Amato
    • 3
  1. 1.Institute for Particle Physics of ETHZ, 5232 Villigen PSI, SwitzerlandCH
  2. 2.Physics Department, Graduate School of Science, Tohoku University, Sendai 980-8578, JapanJP
  3. 3.Paul Scherrer Institute (PSI), 5232 Villigen PSI, SwitzerlandCH

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