Chemical Tuning of Magnetic Properties through Ru/Rh Substitution in Th₇Fe₃‑type FeRh_6–<i>n</i>Ru_<i>n</i>B₃ (<i>n</i> = 1–5) Series

The new quaternary boride series FeRh_6–<i>n</i>Ru_<i>n</i>B₃ (<i>n</i> = 1–5) was synthesized by arc melting and characterized by powder and single-crystal X-ray diffraction (XRD), energy-dispersive X-ray analysis, and superconducting quantum interference device magnetometry. Single-crystal structure refinement showed the distribution of the iron atoms in two of three possible crystallographic 4d metal sites in the structure (Th₇Fe₃-type, space group <i>P</i>6₃<i>mc</i>). Rietveld refinements of the powder XRD data indicated single-phase synthesis of all the members. A linear decrease of the lattice parameters and the unit cell volume with increasing Ru content was found, indicating Vegard’s behavior. Susceptibility measurements show decreasing Curie temperature and magnetic moment (μ_a^5T) recorded at 5 T with increasing Ru content from <i>T</i>_C = 295 K and μ_a^5T = 3.35 μ_B (FeRh₅RuB₃) to <i>T</i>_C = 205 K and μ_a^5T = 0.70 μ_B (FeRhRu₅B₃). The measured coercivities lie between 1.0 and 2.2 kA/m indicating soft to semihard magnetic materials