Journal Article

FZJ-2016-07343

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Europium mixed-valence, long-range magnetic order, and dynamic magnetic response in EuCu$_2$(Si$_x$Ge$_{1 − x}$)$_2$

Nemkovskiy, K. (Corresponding author)FZJ* ; Kozlenko, D. P. ; Alekseev, P. A. ; Mignot, J.-M. ; Menushenkov, A. P. ; Yaroslavtsev, A. A. ; Clementyev, E. S. ; Ivanov, A. S. ; Rols, S. ; Klobes, B. ; Hermann, R.FZJ* ; Gribanov, A. V.

2016
Inst. Woodbury, NY

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Please use a persistent id in citations: http://hdl.handle.net/2128/13431  doi:10.1103/PhysRevB.94.195101

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 fluctuations. 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 field, chemical composition). Recently, similar effects (mixed-valence, Kondo fluctuations, 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 fluctuation can exist even in the magnetic order regime. This paper presents a detailed study of the latter material using different microscopic probes (XANES, Mössbauer 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 fluctuations into the antiferromagnetic state over a sizable composition range below the critical Si concentration xc≈0.65. The sequence of magnetic ground states in the series is shown to reflect the evolution of the magnetic spectral response.

Keyword(s): Magnetic Materials (1st) ; Magnetism (2nd) ; Condensed Matter Physics (2nd)

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Contributing Institute(s):

1. JCNS-FRM-II (JCNS (München) ; Jülich Centre for Neutron Science JCNS (München) ; JCNS-FRM-II)
2. Streumethoden (JCNS-2)

Research Program(s):

1. 524 - Controlling Collective States (POF3-524) (POF3-524)
2. 6212 - Quantum Condensed Matter: Magnetism, Superconductivity (POF3-621) (POF3-621)
3. 6G15 - FRM II / MLZ (POF3-6G15) (POF3-6G15)
4. 6G4 - Jülich Centre for Neutron Research (JCNS) (POF3-623) (POF3-623)

Experiment(s):

1. No specific instrument

Appears in the scientific report 2016

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Database coverage:
; ; ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; IF < 5 ; JCR ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

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