ChemInform Abstract: Tailoring Magnetic Behavior in the Tb‐Au‐Si Quasicrystal Approximant System.

Abstract

Tailoring Magnetic Behavior in the Tb-Au-Si Quasicrystal Approximant System.-"Arc-melting-self-flux" as a new preparative method isemployed to prepare five Tsai-type 1/1 approximant crystals in the Tb-Au-Si system. The method employs a temperature program which oscillates near the melting and nucleation points of the approximants, thus, providing large high-quality single crystals superior to those obtained by e.g. standard arc-melting-annealing. The compounds are prepared from stoichiometric amounts of the elements by repeated homogenization melting (Al 2O3 crucible sealed in stainless steel tubes, complex heating and cooling schedule) and are nearly isostructural with subtle variations (space group Im3, Z = 24, single crystal XRD). The nominal compositions were calculated from the corresponding structure models as Tb(13.6)Au(68.8)Si(17.5), Tb(14.3)Au(69.8)Si(15.9), Tb(14.5)Au(69.5)Si(15.9), Tb(14.9)Au(69.5)Si(15.6), and Tb(15.4)Au(66.9)Si(17.7) (in at%); Two types of atomic clusters which mainly vary at their cluster centers are observed. One type contains a Tb site at the center, the other contains a disordered tetrahedron decorated with Au/Si mixed sites. Both cluster types coexist in the approximants. Magnetic measurements reveal that the magnetic transition temperature decreases as the occupancy of the central Tb site increases (11.5 K for 0% to 8 K for 100% occupancy). Enhanced magneto crystalline anisotropy is observed for the approximants with higher central Tb occupancy. -(GEBRESENBUT*, G. H.; ANDERSSON, M. S.; NORDBLAD, P.; SAHLBERG, M.; PAY GOMEZ, C.; Inorg. Chem. 55 (2016) 5, 2001-2008, http://dx.doi.org/10.1021/acs.inorgchem.5b02286 ; Dep. Chem., Uppsala Univ., S-751 23 Uppsala, Swed.; Eng.) -J. Schramke 20-006