Low-temperature specific-heat and neutron-diffraction studies on Li2Pd3B and Li2Pt3B superconductors
H. Takeya, K. Hirata, K. Yamaura, K. Togano, M. El Massalami, R. Rapp, F. A. Chaves, B. Ouladdiaf
DOI 10.1103/PhysRevB.72.104506 · Physical Review B
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Abstract
Powder neutron diffraction analysis on B11-enriched samples of Li2Pd3B and Li2Pt3B confirms the stability, down to liquid helium temperatures, of their antiperovskite structure (space group P4332). The low-temperature normal-state specific heats (measured within the range 400mK<T<20K and H⩽70kOe) follow a superposition of a linear and a cubic term: for Li2Pd3B the Sommerfeld coefficient γ=9.0(1)mJ∕molK2 and the Debye temperature θD=221(1)K while for Li2Pt3B, γ=7.0(1)mJ∕molK2 and θD=228(1)K. Their thermodynamic superconducting temperatures Tc are, respectively, 7.5(3) K and 2.17(5) K while ΔC∕γTc are 2.0(3) and 1.39(3). The thermal evolution of the superconducting specific heat of Li2Pd3B is Ces(T<Tc)=22γTcexp(−2.1Tc∕T)J∕molK while for Li2Pt3B is Ces(T<Tc)=8.5γTcexp(−1.42Tc∕T)J∕molK. The analysis of these features, within the framework of the strong-coupled theory, suggests that Li2Pt3B is weakly coupled BCS-type superconductor [Tc∕ωlog→0, λ=0.48(2), N(EF)=1.00(2)states∕eV∕formula unit, and 2Δ0∕Tc=3.53] while Li2Pd3B is an intermediate-coupled BCS-type superconductor [Tc∕ωlog=0.068(5), λ=1.09(7), N(EF)=0.91(4)states∕eV∕formula unit, and 2Δ0∕Tc=3.94(4)]. We discuss the reported reduction of Tc with x in the solid solution Li2(PtxPd1−x)3B.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Li2Pd3B Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 7.5 | Pressure not reported | unknown |
| Li2Pt3B Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 2.17 | Pressure not reported | unknown |
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