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Title: Europium mixed-valence, long-range magnetic order, and dynamic magnetic response in EuCu 2 ( Si x Ge 1 - x ) 2

Abstract

In mixed-valence or heavy-fermion systems, the hybridization between local f orbitals and conduction band states can cause the suppression of long-range magnetic order, which competes with strong spin uctuations. Ce- and Yb-based systems have been found to exhibit fascinating physical properties (heavy-fermion superconductivity, non-Fermi-liquid states, etc.) when tuned to the vicinity of magnetic quantum critical points by use of various external control parameters (temperature, magnetic eld, chemical composition). Recently, similar effects (mixed-valence, Kondo uctuations, heavy Fermi liquid) have been reported to exist in some Eu-based compounds. Unlike Ce (Yb), Eu has a multiple electron (hole) occupancy of its 4f shell, and the magnetic Eu 2+ state (4f 7) has no orbital component in the usual LS coupling scheme, which can lead to a quite different and interesting physics. In the EuCu 2(Si xGe 1-x) 2 series, where the valence can be tuned by varying the Si/Ge ratio, it has been reported that a significant valence uctuation can exist even in the magnetic order regime. This paper presents a detailed study of the latter material using different microscopic probes (XANES, Mossbauer spectroscopy, elastic and inelastic neutron scattering), in which the composition dependence of the magnetic order and dynamics across the seriesmore » is traced back to the change in the Eu valence state. In particular, the results support the persistence of valence uctuations into the antiferromagnetic state over a sizable composition range below the critical Si concentration x c ≈ 0:65. In conclusion, the sequence of magnetic ground states in the series is shown to re ect the evolution of the magnetic spectral response.« less

Authors:
 [1];  [2];  [3];  [4];  [5];  [6];  [7];  [8];  [8];  [9];  [10];  [11]
  1. Forschungszentrum JulichGmbH, Garching (Germany)
  2. Frank Lab. of Neutron Physics, Moscow Region (Russia)
  3. National Research Centre "Kurchatov Institute", Moscow (Russia); National Research Nuclear Univ. MEPhI (Moscow Engineering Physics Institute), Moscow (Russia)
  4. Lab. Leon Brillouin-UMR12 CNRS-CEA, Gif-sur-Yvette (France)
  5. National Research Nuclear Univ. MEPhI (Moscow Engineering Physics Institute), Moscow (Russia)
  6. National Research Nuclear Univ. MEPhI (Moscow Engineering Physics Institute), Moscow (Russia); European XFEL GmbH, Schenefeld (Germany)
  7. I Kant Baltic Federal Univ., Kaliningrad (Russia); Institute for Nuclear Research RAS, Moscow (Russia)
  8. Institute Laue-Langevin, Grenoble Cedex (France)
  9. Forschungszentrum Julich GmbH, Julich (Germany)
  10. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  11. Moscow State Univ., Moscow (Russia)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1331099
Alternate Identifier(s):
OSTI ID: 1330601
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 94; Journal Issue: 19; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

Citation Formats

Nemkovski, Krill S., Kozlenko, D. P., Alekseev, Pavel A., Mignot, J. -M., Menushenkov, A. P., Yaroslavtsev, A. A., Clementyev, E. S., Ivanov, Alexander S., Rols, Stephane, Klobes, B., Hermann, Rachel P., and Gribanov, A. V. Europium mixed-valence, long-range magnetic order, and dynamic magnetic response in EuCu2(SixGe1-x)2. United States: N. p., 2016. Web. doi:10.1103/PhysRevB.94.195101.
Nemkovski, Krill S., Kozlenko, D. P., Alekseev, Pavel A., Mignot, J. -M., Menushenkov, A. P., Yaroslavtsev, A. A., Clementyev, E. S., Ivanov, Alexander S., Rols, Stephane, Klobes, B., Hermann, Rachel P., & Gribanov, A. V. Europium mixed-valence, long-range magnetic order, and dynamic magnetic response in EuCu2(SixGe1-x)2. United States. doi:10.1103/PhysRevB.94.195101.
Nemkovski, Krill S., Kozlenko, D. P., Alekseev, Pavel A., Mignot, J. -M., Menushenkov, A. P., Yaroslavtsev, A. A., Clementyev, E. S., Ivanov, Alexander S., Rols, Stephane, Klobes, B., Hermann, Rachel P., and Gribanov, A. V. Tue . "Europium mixed-valence, long-range magnetic order, and dynamic magnetic response in EuCu2(SixGe1-x)2". United States. doi:10.1103/PhysRevB.94.195101. https://www.osti.gov/servlets/purl/1331099.
@article{osti_1331099,
title = {Europium mixed-valence, long-range magnetic order, and dynamic magnetic response in EuCu2(SixGe1-x)2},
author = {Nemkovski, Krill S. and Kozlenko, D. P. and Alekseev, Pavel A. and Mignot, J. -M. and Menushenkov, A. P. and Yaroslavtsev, A. A. and Clementyev, E. S. and Ivanov, Alexander S. and Rols, Stephane and Klobes, B. and Hermann, Rachel P. and Gribanov, A. V.},
abstractNote = {In mixed-valence or heavy-fermion systems, the hybridization between local f orbitals and conduction band states can cause the suppression of long-range magnetic order, which competes with strong spin uctuations. Ce- and Yb-based systems have been found to exhibit fascinating physical properties (heavy-fermion superconductivity, non-Fermi-liquid states, etc.) when tuned to the vicinity of magnetic quantum critical points by use of various external control parameters (temperature, magnetic eld, chemical composition). Recently, similar effects (mixed-valence, Kondo uctuations, heavy Fermi liquid) have been reported to exist in some Eu-based compounds. Unlike Ce (Yb), Eu has a multiple electron (hole) occupancy of its 4f shell, and the magnetic Eu2+ state (4f7) has no orbital component in the usual LS coupling scheme, which can lead to a quite different and interesting physics. In the EuCu2(SixGe1-x)2 series, where the valence can be tuned by varying the Si/Ge ratio, it has been reported that a significant valence uctuation can exist even in the magnetic order regime. This paper presents a detailed study of the latter material using different microscopic probes (XANES, Mossbauer spectroscopy, elastic and inelastic neutron scattering), in which the composition dependence of the magnetic order and dynamics across the series is traced back to the change in the Eu valence state. In particular, the results support the persistence of valence uctuations into the antiferromagnetic state over a sizable composition range below the critical Si concentration xc ≈ 0:65. In conclusion, the sequence of magnetic ground states in the series is shown to re ect the evolution of the magnetic spectral response.},
doi = {10.1103/PhysRevB.94.195101},
journal = {Physical Review B},
number = 19,
volume = 94,
place = {United States},
year = {2016},
month = {11}
}

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