TY - JOUR
T1 - Critical evaluation of Eu valences from LIII-edge x-ray-absorption and Mössbauer spectroscopy of EuNi2Si2-xGex
AU - Wortmann, G.
AU - Nowik, I.
AU - Perscheid, B.
AU - Kaindl, G.
AU - Felner, I.
PY - 1991
Y1 - 1991
N2 - In the quasiternary EuNi2Si2-xGex 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 EuNi2Si0.5Ge1.5 by Eu LIII x-ray-absorption and Eu151 Mössbauer 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, v(LIII), derived from LIII-edge measurements, and the mean Mössbauer isomer shift is only observed if a variation of the recoil-free fraction at the different Eu sites is taken into account. The Eu LIII spectra of EuNi2Ge2, in which the Eu is divalent according to Mössbauer and magnetization measurements, result in v(LIII)=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 EuNi2Si0.5Ge1.5 is in accord with the intermediate-valence character of this compound, which orders ferromagnetically at 25 K.
AB - In the quasiternary EuNi2Si2-xGex 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 EuNi2Si0.5Ge1.5 by Eu LIII x-ray-absorption and Eu151 Mössbauer 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, v(LIII), derived from LIII-edge measurements, and the mean Mössbauer isomer shift is only observed if a variation of the recoil-free fraction at the different Eu sites is taken into account. The Eu LIII spectra of EuNi2Ge2, in which the Eu is divalent according to Mössbauer and magnetization measurements, result in v(LIII)=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 EuNi2Si0.5Ge1.5 is in accord with the intermediate-valence character of this compound, which orders ferromagnetically at 25 K.
UR - http://www.scopus.com/inward/record.url?scp=0000915425&partnerID=8YFLogxK
U2 - 10.1103/PhysRevB.43.5261
DO - 10.1103/PhysRevB.43.5261
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AN - SCOPUS:0000915425
SN - 0163-1829
VL - 43
SP - 5261
EP - 5268
JO - Physical Review B
JF - Physical Review B
IS - 7
ER -