Magnetic and Electrical Properties, 151Eu Mössbauer Spectroscopy, and Chemical Bonding of REAgMg (RE=La, Ce, Eu, Yb) and EuAuMg
✍ Scribed by Dirk Johrendt; Gunter Kotzyba; Henning Trill; Bernd D. Mosel; Hellmut Eckert; Thomas Fickenscher; Rainer Pöttgen†
- Publisher
- Elsevier Science
- Year
- 2002
- Tongue
- English
- Weight
- 411 KB
- Volume
- 164
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
Single-phase samples of REAgMg (RE ؍ La, Ce, Eu, Yb) and EuAuMg were prepared by reacting the elements in sealed tantalum tubes in a high-frequency furnace. LaAgMg and CeAgMg adopt the hexagonal ZrNiAl-type structure, while EuAgMg, YbAgMg, and EuAuMg crystallize with the orthorhombic TiNiSi type. Chemical bonding was exemplarily investigated for EuAgMg and EuAuMg on the basis of TB-LMTO-ASA calculations. Magnetic susceptibility measurements indicate Pauli paramagnetism for LaAgMg and YbAgMg with roomtemperature susceptibilities of 2.4(1)؋10 ؊9 and 1.5(1)؋ 10 ؊9 m 3 /mol, respectively. CeAgMg remains paramagnetic down to 2 K. The experimental magnetic moment of 2.52(2) B /Ce above 50 K is compatible with trivalent cerium. EuAgMg and EuAuMg are paramagnetic above 50 K with experimental magnetic moments of 7.99(5) B /Eu for the silver and 7.80(5) B / Eu for the gold compound, indicating divalent europium. Ferromagnetic ordering is detected at T C ؍ 22.0(3) K (EuAgMg) and T C ؍ 36.5(5) K (EuAuMg). At 4.2 K and 5 T the saturation magnetizations are 7.1(1) and 7.3(1) B /Eu for EuAgMg and EuAuMg, respectively. According to the very small hysteresis, EuAgMg and EuAuMg may be classi5ed as soft ferromagnets. All compounds are metallic conductors. For EuAgMg and Eu-AuMg freezing of spin-disorder scattering is observed below T C . At 78 K 151 Eu MoK ssbauer spectra show isomer shifts of ؊9.00(4) and ؊8.72(8) mm/s for EuAgMg and EuAuMg, respectively. Full magnetic hyper5ne 5eld splitting is detected at 4.2 K with hyper5ne 5elds of 17.4(1) and 18.3(2) T at the europium nuclei of EuAgMg and EuAuMg.
2002 Elsevier Science (USA)