Ferromagnetic Quantum Critical Fluctuations and Anomalous Coexistence of Ferromagnetism and Superconductivity in UCoGe Revealed by Co-NMR and NQR Studies

• Ohta Tetsuya

  Department of Physics, Graduate School of Science, Kyoto University

• Nakai Yusuke

  Department of Physics, Graduate School of Science, Kyoto University

• Ihara Yoshihiko

  Department of Physics, Graduate School of Science, Kyoto University

• Ishida Kenji

  Department of Physics, Graduate School of Science, Kyoto University

• Deguchi Kazuhiko

  Department of Physics, Graduate School of Science, Nagoya University

• Sato Noriaki K.

  Department of Physics, Graduate School of Science, Nagoya University

• Satoh Isamu

  Institute for Materials Research, Tohoku University

Abstract

Co nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) studies were carried out for the recently discovered UCoGe, in which the ferromagnetic and superconducting (SC) transitions are reported to occur at T_Curie∼3 K and T_S∼0.8 K [Huy et al.: Phys. Rev. Lett. 99 (2007) 067006], in order to investigate the coexistence of ferromagnetism and superconductivity as well as the normal-state and SC properties from a microscopic point of view. From the nuclear spin–lattice relaxation rate 1⁄T₁ and Knight-shift measurements, we confirm that ferromagnetic fluctuations that possess a quantum critical character are present above T_Curie and also the occurrence of a ferromagnetic transition at 2.5 K in our polycrystalline sample. The magnetic fluctuations in the normal state show that UCoGe is an itinerant ferromagnet similar to ZrZn₂ and YCo₂. The onset SC transition is identified at T_S∼0.7 K, below which 1⁄T₁ arising from 30% of the volume fraction starts to decrease due to the opening of the SC gap. This component of 1⁄T₁, which follows a T³ dependence in the temperature range 0.3–0.1 K, coexists with the magnetic components of 1⁄T₁ showing a \\sqrtT dependence below T_S. From the NQR measurements in the SC state, we suggest that the self-induced vortex state is realized in UCoGe.

Journal

• Journal of the Physical Society of Japan

  Journal of the Physical Society of Japan 77 (2), 023707-023707, 2008

  THE PHYSICAL SOCIETY OF JAPAN

Keywords

• UCoGe
• ferromagnetic superconductor
• Co-NMR and NQR
• coexistence

Details

• CRID: 1390282679175051904
• NII Article ID: 130005436319
• NII Article ID: 110006613875
• NII Article ID: 210000107082
• NII Book ID: AA00704814
• DOI: 10.1143/jpsj.77.023707
• ISSN: 13474073
• ISSN: 00319015
• NDL BIB ID: 9377247
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I9377247
• Web Site: https://journals.jps.jp/doi/pdf/10.1143/JPSJ.77.023707
• Text Lang: en
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
• Abstract License Flag: Disallowed