Eu₁₁Zn₄Sn₂As₁₂: A Ferromagnetic Zintl Semiconductor with a Layered Structure Featuring Extended Zn₄As₆ Sheets and Ethane-like Sn₂As₆ Units

We report the synthesis, structure, and magnetic properties of a new Zintl phase and structure type, Eu11Zn4Sn2As12. The structure and composition of this phase have been established by single-crystal X-ray diffraction and electron microprobe analysis. Eu11Zn4Sn2As12 crystallizes in monoclinic space group C2/c (No. 15) with the following lattice parameters: a = 7.5679(4) Å, b = 13.0883(6) Å, c = 31.305(2) Å, and β = 94.8444(7)° [R1 = 0.0398; wR2 = 0.0633 (all data)]. The anisotropic structural features staggered ethane-like [Sn2As6]12– units and infinite ∞2[Zn2As3]5– sheets extended in the a–b plane. Eu cations fill the space between these anionic motifs. Temperature-dependent magnetic properties and magnetoresistance of this Zintl phase have been studied, and the electronic structure and chemical bonding were elucidated using first-principles quantum chemical calculations (TB-LMTO-ASA). Quantum chemical calculations show that the ethane-like units can be considered as consisting of covalent single bonds; however, the ∞2[Zn2As3]5– sheets are best described with delocalized bonding and there is evidence of Eu–As interactions. Temperature-dependent magnetization and transport properties between 2 and 300 K show a ferromagnetic transition at 15 K, a band gap of 0.04 eV, and negative colossal magnetoresistance.