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Rare earth-copper-magnesium intermetallics: crystal structure of CeCuMg, magnetocaloric effect of GdCuMg and physical properties of the Laves phases RECu4Mg (RE=Sm, Gd, Tb, Tm)

Rare earth-copper-magnesium intermetallics: crystal structure of CeCuMg, magnetocaloric effect of... AbstractThe intermetallic magnesium compounds CeCuMg and GdCuMg as well as the ternary Laves phases RECu4Mg (RE=Sm, Gd–Tm) were synthesized from the elements by different annealing sequences in high-frequency and muffle furnaces using niobium ampoules as crucibles. All samples were characterized through the lattice parameters using X-ray powder diffraction (Guinier technique). Two structures were refined from single-crystal X-ray diffractometer data: a=764.75(6), c=414.25(4) pm, space group P6̅2m, wR2=0.0389, 338 F2 values, 15 parameters for CeCuMg (ZrNiAl type) and a=723.18(2) pm, space group F4̅3m, wR2=0.0818, 91 F2 values, eight parameters for Gd1.06(3)Cu4Mg0.94(3) (MgCu4Sn type). The Laves phase shows a small homogeneity range (Gd/Mg mixing). An investigation of the magnetocaloric effect (MCE) of ferromagnetic GdCuMg (ZrNiAl type; TC=82 K) revealed a magnetic entropy change of ΔSM=6.5 J kg−1 K−1 and a relative cooling power of RCP=260 J kg−1 for a field change from 0 to 70 kOe, classifying GdCuMg as a moderate magnetocaloric material for the T=80 K region. Of the Laves phases RECu4Mg, SmCu4Mg shows van-Vleck paramagnetism above a Néel temperature of 10.8(5) K, whereas GdCu4Mg and TbCu4Mg undergo antiferromagnetic phase transitions at about 48 and 30 K, respectively. TmCu4Mg shows Curie-Weiss behavior in the entire temperature range. The electrical resistivity of SmCu4Mg and the specific heat capacity of GdCu4Mg were measured for further characterization. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Zeitschrift für Naturforschung B de Gruyter

Rare earth-copper-magnesium intermetallics: crystal structure of CeCuMg, magnetocaloric effect of GdCuMg and physical properties of the Laves phases RECu4Mg (RE=Sm, Gd, Tb, Tm)

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References (63)

Publisher
de Gruyter
Copyright
©2018 Walter de Gruyter GmbH, Berlin/Boston
ISSN
0932-0776
eISSN
1865-7117
DOI
10.1515/znb-2018-0191
Publisher site
See Article on Publisher Site

Abstract

AbstractThe intermetallic magnesium compounds CeCuMg and GdCuMg as well as the ternary Laves phases RECu4Mg (RE=Sm, Gd–Tm) were synthesized from the elements by different annealing sequences in high-frequency and muffle furnaces using niobium ampoules as crucibles. All samples were characterized through the lattice parameters using X-ray powder diffraction (Guinier technique). Two structures were refined from single-crystal X-ray diffractometer data: a=764.75(6), c=414.25(4) pm, space group P6̅2m, wR2=0.0389, 338 F2 values, 15 parameters for CeCuMg (ZrNiAl type) and a=723.18(2) pm, space group F4̅3m, wR2=0.0818, 91 F2 values, eight parameters for Gd1.06(3)Cu4Mg0.94(3) (MgCu4Sn type). The Laves phase shows a small homogeneity range (Gd/Mg mixing). An investigation of the magnetocaloric effect (MCE) of ferromagnetic GdCuMg (ZrNiAl type; TC=82 K) revealed a magnetic entropy change of ΔSM=6.5 J kg−1 K−1 and a relative cooling power of RCP=260 J kg−1 for a field change from 0 to 70 kOe, classifying GdCuMg as a moderate magnetocaloric material for the T=80 K region. Of the Laves phases RECu4Mg, SmCu4Mg shows van-Vleck paramagnetism above a Néel temperature of 10.8(5) K, whereas GdCu4Mg and TbCu4Mg undergo antiferromagnetic phase transitions at about 48 and 30 K, respectively. TmCu4Mg shows Curie-Weiss behavior in the entire temperature range. The electrical resistivity of SmCu4Mg and the specific heat capacity of GdCu4Mg were measured for further characterization.

Journal

Zeitschrift für Naturforschung Bde Gruyter

Published: Dec 19, 2018

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