Magnetic and Electrical Properties, 151Eu Mössbauer Spectroscopy, and Chemical Bonding of REAgMg (RE=La, Ce, Eu, Yb) and EuAuMg

• Published in: Journal of solid state chemistry 2002-03, Vol.164 (2), p.201-209
• Main Authors: Johrendt, Dirk, Kotzyba, Gunter, Trill, Henning, Mosel, Bernd D., Eckert, Hellmut, Fickenscher, Thomas, Pöttgen†, Rainer
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron density of states and band structure of crystalline solids; Electron states; electronic structure; Exact sciences and technology; Magnetic properties and materials; Magnetic resonances and relaxations in condensed matter, mössbauer effect; magnetism; Mossbauer effect; other γ-ray spectroscopy; Mössbauer effect; other γ-ray spectroscopy; mössbauer spectroscopy; Other ferromagnetic metals and alloys; Other metals and alloys; Physics; Studies of specific magnetic materials
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1006/jssc.2001.9460

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 investigatedfor EuAgMg and EuAuMg on the basis of TB-LMTO-ASAcalculations. Magnetic susceptibility measurements indicatePauli paramagnetism for LaAgMg and YbAgMg with room-temperature susceptibilities of 2.4(1)×10−9 and 1.5(1)×10−9 m3/mol, respectively. CeAgMg remains paramagnetic down to 2 K. The experimental magnetic moment of 2.52(2) μB/Ce above 50 K is compatible with trivalent cerium. EuAgMg and EuAuMg are paramagnetic above 50 K with experimentalmagnetic moments of 7.99(5) μB/Eu for the silver and 7.80(5) μB/Eu for the gold compound, indicating divalent europium. Ferromagnetic ordering is detected at TC=22.0(3) K (EuAgMg) and TC=36.5(5) K (EuAuMg). At 4.2 K and 5 T the saturation magnetizations are 7.1(1) and 7.3(1) μB/Eu for EuAgMg and EuAuMg, respectively. According to the very small hysteresis, EuAgMg and EuAuMg may be classified as soft ferromagnets. All compounds are metallic conductors. For EuAgMg and EuAuMg freezing of spin-disorder scattering is observed below TC. At 78 K 151Eu Mössbauer spectra show isomer shifts of −9.00(4) and −8.72(8) mm/s for EuAgMg and EuAuMg, respectively. Full magnetic hyperfine field splitting is detected at 4.2 K with hyperfine fields of 17.4(1) and 18.3(2) T at the europium nuclei of EuAgMg and EuAuMg.