Superconductivity in the $\eta$-carbide-type oxides Zr4Rh2Ox

Abstract

We report on the synthesis and the superconductivity of Zr${}_4$Rh${}_2$O${}_x$ ($x$ = 0.4, 0.5, 0.6, 0.7, 1.0). These compounds crystallize in the $\eta$-carbide structure, which is a filled version of the complex intermetallic Ti${}_2$Ni structure. We find that in the system Zr${}_4$Rh${}_2$O${}_x$, already a small amount ($x$ $\ge$ 0.4) of oxygen addition stabilizes the $\eta$-carbide structure over the more common intermetallic CuAl${}_2$ structure-type, in which Zr${}_2$Rh crystallizes. We show that Zr${}_4$Rh${}_2$O${}_{0.7}$ and Zr${}_4$Rh${}_2$O are bulk superconductors with critical temperatures of $T_c\approx$ 2.8 K and 4.7 K in the resistivity, respectively. Our analysis of the superconducting properties reveal both compounds to be strongly type-II superconductors with critical fields up to ${\mu }_0{H}_{c1}$(0) $\approx$ 8.8 mT and ${\mu }_0{H}_{c2}$(0) $\approx$ 6.08 T. Our results support that the $\eta$-carbides are a versatile family of compounds for the investigation of the interplay of interstitial doping on physical properties, especially for superconductivity.

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Cited by in corpus (5)

• Superconductivity with High Upper Critical Field in the Cubic Centrosymmetric $\eta$-Carbide Nb${}_4$Rh${}_2$C${}_{1-\delta }$
• Group-9 Transition Metal Suboxides Adopting the Filled-Ti${}_2$Ni Structure: A Class of Superconductors Exhibiting Exceptionally High Upper Critical Fields
• Superconductivity with a Violation of Pauli Limit and Evidences for Multigap in $\eta$-Carbide type Ti${}_4$Ir${}_2$O
• Discovery of the Type-II Superconductor Ta${}_4$Rh${}_2$C${}_{1-\delta }$ with a High Upper Critical Field
• Structure, Composition, and High-Field Superconductivity in Metal-Rich $\eta$-Carbide-Type Compounds