Critical evaluation of Eu valences from L sub III -edge x-ray-absorption and Moessbauer spectroscopy of EuNi sub 2 Si sub 2 minus x Ge sub x

Journal Article · Fri Mar 01 00:00:00 EST 1991 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.43.5261· OSTI ID:5693103

Wortmann, G; Nowik, I; Perscheid, B; Kaindl, G ^[1]; Felner, I ^[2]

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1. Institut fuer Experimentalphysik, Freie Universitaet Berlin, D-1000 Berlin 33, Germany (DE)
2. Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem, (Israel)

In the quasiternary EuNi{sub 2}Si{sub 2{minus}{ital x}}Ge{sub {ital x}} system most of the Eu ions exhibit an intermediate-valence character, depending on the number of Si neighbors and the temperature. A detailed study of EuNi{sub 2}Si{sub 0.5}Ge{sub 1.5} by Eu {ital L}{sub III} x-ray-absorption and {sup 151}Eu Moessbauer spectroscopy reveals a sharp temperature-induced valence change, which is more complete than in any other Eu system. A linear correlation between the mean Eu valence, {ital v}({ital L}{sub III}), derived from {ital L}{sub III}-edge measurements, and the mean Moessbauer isomer shift is only observed if a variation of the recoil-free fraction at the different Eu sites is taken into account. The Eu {ital L}{sub III} spectra of EuNi{sub 2}Ge{sub 2}, in which the Eu is divalent according to Moessbauer and magnetization measurements, result in {ital v}({ital L}{sub III})=2.15, which is similar to other divalent intermetallic Eu systems. This observation is attributed to final-state effects due to covalency. The magnetic susceptibility of EuNi{sub 2}Si{sub 0.5}Ge{sub 1.5} is in accord with the intermediate-valence character of this compound, which orders ferromagnetically at 25 K.

• OSTI ID: 5693103
• Journal Information: Physical Review, B: Condensed Matter; (USA), Vol. 43:7; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
EUROPIUM 151
MOESSBAUER EFFECT
EUROPIUM ALLOYS
VALENCE
GERMANIUM ALLOYS
NICKEL ALLOYS
SILICON ALLOYS
ABSORPTION SPECTRA
LOW TEMPERATURE
MAGNETIC SUSCEPTIBILITY
MEDIUM TEMPERATURE
TEMPERATURE DEPENDENCE
ULTRALOW TEMPERATURE
VERY LOW TEMPERATURE
X-RAY SPECTRA
ALLOYS
EUROPIUM ISOTOPES
INTERMEDIATE MASS NUCLEI
ISOTOPES
MAGNETIC PROPERTIES
NUCLEI
ODD-EVEN NUCLEI
PHYSICAL PROPERTIES
RARE EARTH ALLOYS
RARE EARTH ISOTOPES
RARE EARTH NUCLEI
SPECTRA
STABLE ISOTOPES
360104* - Metals & Alloys- Physical Properties