Structure and transport properties of the R 2 Co 2 Al compounds (R=Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Y)

✍ Scribed by Pani, M.; Merlo, F.; Fornasini, M. L.

• Book ID: 119993488
• Publisher: Oldenbourg Wissenschaftsverlag
• Year: 2002
• Tongue: English
• Weight: 336 KB
• Volume: 217
• Category: Article
• ISSN: 2194-4946
• DOI: 10.1524/zkri.217.7.415.23677

✦ Synopsis

Abstract

The new R~2~Co~2~Al compounds (R=Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Y), studied by single crystal and powder X-ray diffraction, crystallize with the W~2~CoB~2~ structure type. Pr~2~Co~2~Al is dimorphic, showing also its own monoclinic structure (a=9.595 Å, b=5.602 Å, c=7.753 Å, β=103.89°), which is closely related to the W~2~CoB~2~ type. Both structures are based on different packing of chains of cobalt-centred double trigonal prisms formed by rare earth and aluminum atoms. The electrical resistivity, measured in the 13-300K temperature range for all phases (save Y~2~Co~2~Al), always shows a transition point at temperatures going from 14K for Tm~2~Co~2~Al to 94K for Tb~2~Co~2~Al. As already found for Gd~2~Co~2~Al, these points should correspond to an order-disorder magnetic transition, and the deviations from de Gennes scaling indicate the influence of both the crystalline electric field and the strong coupling between 4f and conduction electrons.