The coloring problem in intermetallics: bonding and properties of Tb3Zn3.6Al7.4 with the La3Al11 structure type

Abstract

<p>Single crystals of the new compound Tb₃Zn_3.6(1)Al_7.4(1) were obtained from Al and Zn-rich ternary solutions. The title compound crystallizes in the orthorhombic La₃Al₁₁ structure type (space group <em>Immm</em> (No. 71), <em>Z</em> = 2; <em>a</em> = 4.2334(1) Å, <em>b</em> = 9.9725(3) Å, <em>c</em> = 12.4659(1) Å). The inverse susceptibility above ca. 50 K shows Curie-Weiss behavior, and a metamagnetic transition is apparent in the <em>T</em> = 2 K field-dependent magnetization around <em>H_c</em> ∼ 20 kG. The resistivity increases with temperature in a roughly linear fashion, indicating the metallic character of this material. TB-LMTO-ASA electronic structure calculations indicate that this new intermetallic phase has all bonding states optimized in the [Zn_4–xAl_7+x] network, which classifies this compound among the so-called “polar intermetallics”. The calculations also provide a rationalization of the nonrandom ordering of Zn and Al atoms, which can be attributed to optimizing (Zn, Al)—(Zn, Al) orbital interactions.</p>