Superconductivity in Y₄RuGe₈ with a Vacancy-Ordered CeNiSi₂-Type Superstructure

Abstract

We report a new compound, Y4RuGe8, with a transition metal vacancy-ordered CeNiSi2-type superstructure, which has a superconducting transition at 1.3 K. Y4RuGe8 crystals were grown by indium flux at relatively low temperatures (below 1273 K), which makes it possible to stabilize such a vacancy-ordered phase. The crystal structure of Y4RuGe8 was solved by single-crystal X-ray diffraction and confirmed by transmission electron microscopy. The as-grown Y4RuGe8 crystals are always twinned, crystallizing in the space group P1̅ (no. 2) with the lattice parameters a = 5.7680(1) Å, b = 8.2042(2) Å, c = 11.5093(3) Å, α = 79.696(1)°, β = 88.491(1)°, and γ = 79.637(2)°; this structure is a superstructure deriving from the higher symmetry CeNiSi2-type structure (Cmcm, no. 63) due to the ordering of Ru vacancies. The ordering of Ru sites breaks slightly distorted Ge planes in the CeNiSi2 prototype into infinite cis–trans Ge chains in Y4RuGe8. The presence of bulk superconductivity in Y4RuGe8 is well supported by zero resistance and a jump in specific heat at the critical transition temperature. The Sommerfeld coefficient (19 mJ K–2 mol–1) of the specific heat is greater than that (11 mJ K–2 mol–1) estimated using the bare density of states (4.7 states/eV/f.u.) from first-principles calculations. The ab initio calculations indicate that 4d electrons of both Y and Ru and 4p electrons of Ge are the main contributors to the total density of states at the Fermi level in Y4RuGe8.

Investigating the An+1BnX3n+1 Homologous Series: A New Platform for Studying Magnetic Praseodymium Based Intermetallics

“…Unexpectedly, raising the Sn concentration of the reaction has been the most successful method of obtaining phase pure homologous series members, despite producing the byproduct Pr 2 Co 3 Ge 5 . This is similar to recent findings regarding Y 4 RuGe 8 . The possibility of altering the flux concentration to isolate different n members presents a promising new method of reaction tuning that has inspired an investigation into in situ X-ray powder diffraction methods − and thermal analysis , to understand how changing flux conditions influence the formation of homologous series members and other related phases. , …”

“…This is similar to recent findings regarding Y 4 RuGe 8 . 80 The possibility of altering the flux concentration to isolate different n members presents a promising new method of reaction tuning that has inspired an investigation into in situ X-ray powder diffraction methods 81−83 and thermal analysis 84,85 to understand how changing flux conditions influence the formation of homologous series members and other related phases. 86,87 Despite these structural challenges, the Pr n+1 Co n Ge 3n+1 series presents new opportunities for 4f 2 electron systems.…”

Competition of magnetocrystalline anisotropy of uranium layers and zigzag chains inUNi0.34Ge2single crystals

“…To rule out the possibility for an ordered Ni-site occupancy, recently reported for different ternary rare earth germanides, [27][28][29] electron diffraction has been performed. The SAED patterns along various zone axes (Fig.…”

Competition of Magnetocrystalline Anisotropy of Uranium Layers and Zig-Zag Chains in UNi$_{0.34}$Ge$_2$ Single Crystals

“…To rule out the possibility for an ordered Ni-site occupancy, recently reported for different ternary rare earth germanides, [27][28][29] electron diffraction has been performed. The SAED patterns along various zone axes (Fig.…”