Superconducting and calorimetric properties of the quaternary borocarbide superconductor LaPd2B2C

Abstract

A superconducting transition temperature Tc of 1.8 K with a transition width of 1.4–2.2 K and a diamagnetic onset as high as 4.6 K are reported for a metastable LaPd2B2C compound with the LuNi2B2C-type structure. The low-temperature normal-state specific-heat data yield an electronic-term coefficient γ of 7.1 mJ/mol K2, a Debye temperature θD of 310 K, and a bulk superconducting heat-capacity-jump ratio ΔC/γTc of 1.4. The systematic variation of Tc for the metastable compounds in the RPd2B2C system (R=Y, Th, Th1−xLax, La) is correlated with the Pd-Pd nearest-neighbor in-plane distance d. A longer d value of 2.797 Å was observed for 1.8-K LaPd2B2C superconductor while an optimum d value of 2.652 Å was reported for 23-K YPd2B2C. Small Pd-Pd wave function overlapping, along with the observed small specific-heat γ value and normal-state Pauli paramagnetic susceptibility of LaPd2B2C, suggest that the variation of the Pd(4d)-dominated conduction band and thus the Fermi-level density of states N(EF) are the determining factors for the Tc variation of the present system.

Source-reported materials — not catalogue approval

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