Si-induced superconductivity and structural transformations in DyRh4B4

DyRh4B4 has been known to crystallize in the primitive tetragonal (pt)-structure and to exhibit a ferromagnetic transition at 12 K, the highest magnetic transition temperature in the entire series of the RRh4B4 materials [For an extensive review on the magnetic and superconducting properties on the ternary superconductors, including RRh4B4, see, for example, Ø. Fischer, in: K.H.J. Buschow, E.P. Wohlfarth (Eds.), Ferromagnetic Materials, vol. 5, Elsevier Science Publishers B.V., 1990 (Chapter 6)]. We show here that our silicon-added samples of the nominal composition DyRh4B4Si0.2 exhibit superconductivity below Tc ∼ 4.5 K and an antiferromagnetic transition below TN ∼ 2.7 K. The 12 K transition observed in the pt-DyRh4B4 is completely suppressed. Our annealed samples mainly consist of domains of the chemical composition DyRh3.9B4.2Si0.08. These domains contain two crystallographic phases belonging to the body-centred tetragonal (bct)-structure and the orthorhombic (o)-structure. We have reasons to suggest that superconductivity and antiferromagnetic ordering arise from bct-DyRh4B4 phase and, therefore, coexist below TN ∼ 2.7 K.