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Superconductivity in the Nb-Ru-Ge σ phase

Author(s): Carnicom, Elizabeth M.; Xie, Weiwei; Sobczak, Zuzanna; Kong, Tai; Klimczuk, Tomasz W.; et al

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Abstract: © 2017 American Physical Society. We show that the previously unreported ternary σ-phase material Nb20.4Ru5.7Ge3.9 (Nb0.68Ru0.19Ge0.13) is a superconductor with a critical temperature of 2.2 K. Temperature-dependent magnetic susceptibility, resistance, and specific-heat measurements were used to characterize the superconducting transition. The Sommerfeld constant γ for Nb20.4Ru5.7Ge3.9 is 91mJmolf.u.-1K-2 (∼3mJmolatom-1K-2) and the specific-heat anomaly at the superconducting transition, ΔC/γTc, is approximately 1.38. The zeroerature upper critical field [μ0Hc2(0)] was estimated to be 2 T by resistance data. Field-dependent magnetization data analysis estimated μ0Hc1(0) to be 5.5 mT. Thus, the characterization shows Nb20.4Ru5.7Ge3.9 to be a type-II BCS superconductor. This material appears to be the first reported ternary phase in the Nb-Ru-Ge system, and the fact that there are no previously reported binary Nb-Ru, Nb-Ge, or Ru-Ge σ phases shows that all three elements are necessary to stabilize the material. An analogous σ phase in the Ta-Ru-Ge system did not display superconductivity above 1.7 K, which suggests that electron count cannot govern the superconductivity observed. Preliminary characterization of a possible superconducting σ phase in the Nb-Ru-Ga system is also reported.
Publication Date: Dec-2017
Electronic Publication Date: 7-Dec-2017
Citation: Carnicom, E.M., Xie, W., Sobczak, Z., Kong, T., Klimczuk, T., Cava, R.J. (2017). Superconductivity in the Nb-Ru-Ge σ phase. Physical Review Materials, 1 (7), 10.1103/PhysRevMaterials.1.074802
DOI: doi:10.1103/PhysRevMaterials.1.074802
EISSN: 2475-9953
Pages: 1.7:074802-1 - 074802-7
Type of Material: Journal Article
Journal/Proceeding Title: Physical Review Materials
Version: Final published version. This is an open access article.
Notes: Physical Review Materials. Volume 1, Issue 7, 7 December 2017, Article number 074802.

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