Homoatomic Clustering in the Intermediate Valence Compounds Yb1−yAl3−xSix and Yb1−yAl3−xGex

✍ Scribed by Jing-Tai Zhao; Walter Schnelle; Yuri Grin

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 452 KB
• Volume: 163
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2001.9379

✦ Synopsis

Two new phases, Yb 1؊x Al 3؊x Si x and Yb 1؊y Al 3؊x Ge x , were found by systematic investigations of the according ternary systems. The crystal structures of Yb 1؊y Al 2.8 Si 0.2 and Yb 1؊y Al 2.8 Ge 0.2 (defect HT-PuAl 3 type) were studied by X-ray powder methods (CuK 1 radiation, ‫؍‬ 1.54056 A > , hexagonal system, space group P6 3 /mmc (No. 194), a ‫؍‬ 6.009(1) and 6.015(1) A > , c ‫؍‬ 14.199(2) and 14.241(5) A > , V ‫؍‬ 444.0(2) and 446.2(3) A > 3 , 93 and 92 re6ections, and 8200 and 8000 pro5le points for silicide and germanide, respectively). Full pro5le re5nements with 11 and 13 structural parameters resulted in R I ‫؍‬ 0.049 and 0.054, and R p ‫؍‬ 0.088 and 0.104, respectively. The ternary structures are distorted closest packings in comparison with the binary YbAl 3 compound with AuCu 3 -type structure. They are characterized by the formation of Al 3 -, Si 3 -, and Ge 3 -homoatomic clusters and aluminum networks. Magnetization measurements show that both the silicide and germanide are valence 6uctuation compounds with enhanced electronic density of states at the Fermi level similar to the binary YbAl 3 . The characteristic maximum of the magnetic susceptibility increases from +120 K for YbAl 3 to +140 K for Yb 1؊y Al 2.8 Si 0.2 or Yb 1؊y Al 2.8 Ge 0.2 and further to +150 K for Yb 1؊y Al 2.75 Si 0.25 . The S-shape of the electrical resistivity curves is also characteristic of valence 6uctuations.