Valence crossover of Ce ions in CeCu2Si2under high pressure-pressure dependence of the unit cell volume and the NQR frequency

Tatsuo C. Kobayashi, Kenji Fujiwara, Keiki Takeda, Hisatomo Harima, Yoichi Ikeda, Takafumi Adachi, Yasuo Ohishi, Christoph Geibel, Frank Steglich

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15 Citations (Scopus)


The pressure dependence of the valence of Ce ions in CeCu 2Si2has been investigated by means of X-ray powder diffraction (XRPD) and nuclear quadrupole resonance (NQR) measurements. The high-pressure XRPD measurements were carried out at 12 K for CeCu 2Si2and CeCu2Ge2. Precise measurements under smoothly-applied pressure were achieved through the selection of the gasket material of a diamond anvil cell. The jump of the unit cell volume, which was reported previously in CeCu2Ge2, was not observed within the experimental accuracy, indicating the absence of a first-order valance transition. The pressure dependence of 63Cu-NQR frequency vqmeasured in CeCu2Si2was compared with that calculated from the measured lattice parameters. The vq's were calculated for the two cases of LaCu2Si2and CeCu 2Si2, corresponding to localized and itinerant cases for 4f electrons, respectively. The measured and calculated slopes dvQ/dP show good agreement. A small but significant deviation from the pressure-linear dependence in vqwas observed in the narrow pressure range of 3.9-4.5 GPa, indicating a valence crossover adjacent to the critical end point.

Original languageEnglish
Article number114701
Journaljournal of the physical society of japan
Issue number11
Publication statusPublished - Nov 2013


  • Heavy fermion
  • High pressure
  • NQR
  • Superconductivity
  • X-ray diffraction

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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