Crystal Structure, Chemical Bonding and Magnetism Studies for Three Quinary Polar Intermetallic Compounds in the (Eu1-xCax)(9)In-8(Ge1-ySny)(8) (x=0.66, y=0.03) and the (Eu1-xCax)(3)In(Ge3-ySn1+y) (x=0.66, 0.68; y=0.13, 0.27) Phases

Abstract

Three quinary polar intermetallic compounds in the (Eu1-xCax)(9)In-8(Ge1-ySny)(8) (x = 0.66, y = 0.03) and the (Eu1-xCax)(3)In(Ge3-ySn1+y) (x = 0.66, 0.68; y = 0.13, 0.27) phases have been synthesized using the molten In-metal flux method, and the crystal structures are characterized by powder and single-crystal X-ray diffractions. Two orthorhombic structural types can be viewed as an assembly of polyanionic frameworks consisting of the In(Ge/Sn)(4) tetrahedral chains, the bridging Ge-2 dimers, either the annulene-like 12-membered rings for the (Eu1-xCax)(9)In-8(Ge1-ySny)(8) series or the cis-trans Ge/Sn-chains for the (Eu1-xCax)(3)In(Ge3-ySn1+y) series, and several Eu/Ca-mixed cations. The most noticeable difference between two structural types is the amount and the location of the Sn-substitution for Ge: only a partial substitution (11%) occurs at the In(Ge/Sn)(4) tetrahedron in the (Eu1-xCax)(9)In-8(Ge1-ySny)(8) series, whereas both a complete and a partial substitution (up to 27%) are observed, respectively, at the cis-trans Ge/Sn-chain and at the In(Ge/Sn)(4) tetrahedron in the (Eu1-xCax)(3)In(Ge3-ySn1+y) series. A series of tight-binding linear muffin-tin orbital calculations is conducted to understand overall electronic structures and chemical bonding among components. Magnetic susceptibility measurement indicates a ferromagnetic ordering of Eu atoms below 5 K for Eu1.02(1)Ca1.98InGe2.87(1)Sn1.13.