title: Ladders of a magnetically active element in the structure of the novel complex boride Ti9Fe2Ru18B8: synthesis, structure, bonding, and magnetism.
abstract: Polycrystalline samples and single crystals of the complex boride Ti9Fe2Ru18B8 were synthesized by arc-melting the elements and characterized by single-crystal X-ray diffraction and energy-dispersive X-ray analysis. Ti9Fe2Ru18B8 is a new substitutional variant of the Zn11Rh18B8 structure type, space group P4/mbm (No. 127), whose remarkable feature is that it contains one-dimensional chains of dumbbells of magnetically active Fe atoms, which form "ladders" along the c axis. The Fe-Fe distance within a dumbbell is 2.489(2) A, and the Fe2-Fe2 distance between two dumbbells is 2.968(1) A; in contrast, the chains are well-separated from each other by distances of at least 11.217(2) A. According to the results of tight-binding electronic structure calculations, Ru-B and Ti-Ru contacts are responsible for the structural robustness, while Fe-Fe interactions influence the magnetic behavior. According to magnetization measurements, Ti9Fe2Ru18B8 orders ferromagnetically between 10 and approximately 200 K. A model for ferromagnetism in this ladder-based structure identifies ferromagnetic coupling among neighboring spin-triplet Fe2 dimers along the c axis as the origin of the magnetic behavior.
authors.affiliation: Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, D-52056 Aachen, Germany. boniface.fokwa@ac.rwth-aachen.de
authors.forename: Boniface P T
authors.initials: BP
authors.lastname: Fokwa
authors.forename: German D
authors.initials: GD
authors.lastname: Samolyuk
authors.forename: Gordon J
authors.initials: GJ
authors.lastname: Miller
authors.forename: Richard
authors.initials: R
authors.lastname: Dronskowski