Triangular Arrangement of Ferromagnetic Iron Chains in the High-T C Ferromagnet TiFe 1-x Os 2+x B 2 .

Transition-metal borides (TMBs) containing B n -fragment (n>3) have recently gained interest for their ability to enable exciting magnetic materials. Herein, we show that the B 4 -containing TiFe 0.64(1) Os 2.36(1) B 2 is a new ferromagnetic TMB with a Curie temperature of 523(2) K and a Weiss constant of 554(3) K, originating from the chain of M 3 -triangles (M=64 %Fe+36 %Os). The new phase was synthesized from the elements by arc-melting, and its structure was elucidated by single-crystal X-ray diffraction. It belongs to the Ti 1+x Os 2-x RuB 2 -type structure (space group P 6 ‾ 2 m, no. 189) and contains trigonal-planar B 4 boron fragments [B-B distance of 1.87(4) Å] interacting with M 3 -triangles [M-M distances of 2.637(8) Å and 3.0199(2) Å]. The experimental results were supported by computational calculations based on the ideal TiFeOs 2 B 2 composition, which revealed strong ferromagnetic interactions within and between the Fe 3 -triangles. This discovery represents the first magnetically ordered Os-rich TMB, thus it will help expand our knowledge of the role of Os in low-dimensional magnetism of intermetallics and enable the design of such materials in the future.