Determination of a new structure type in the Sc–Fe–Ge–Sn system

Abstract

A new structure type has been discovered in the system Sc–Fe–Ge–Sn by employing Sn as a flux medium. According to single crystal X-ray diffraction, the new structure has a composition of Sc4Fe5Ge6.10(3)Sn1.47(2) and crystallizes in the space group Immm (No. 71, oI144) with lattice parameters of a=5.230(1)Å, b=13.467(3)Å, and c=30.003(6)Å. The structure is composed of square anti-prismatic clusters that are condensed into zig-zag chains along the [010] direction. These chains are further condensed through a split Sn/Ge position, forming a three-dimensional network. Magnetization measurements indicate an antiferromagnetic phase transition near 240K. Electronic structure calculations identified the most favorable bonding network in this new system. Using crystal orbital Hamilton population (COHP) curves and their integrated values (ICOHP), a polar intermetallic bonding network involving Sc–Ge as well as Fe–Sn and Fe–Ge contacts can be assigned to this new structure type.