MgPd2Sb : A Mg-based Heusler-type superconductor

Abstract

We report the synthesis and physical properties of a new full Heusler compound, MgPd2Sb, which we found to show superconductivity below Tc = 2.2 K. MgPd2Sb was obtained by a two-step solid state reaction method and its purity and cubic crystal structure (F m-3m, a = 6.4523(1) Å) were confirmed by powder x-ray diffraction. Normal and superconducting states were studied by electrical resistivity, magnetic susceptibility and heat capacity measurements. The results show that MgPd2Sb is a type-II, weak coupling superconductor (λep = 0.56). The observed pressure dependence of Tc (ΔTc/p ≈ -0.23 K/GPa) is one of the strongest reported for a superconducting Heusler compound. The electronic structure, phonons and electron-phonon coupling in MgPd2Sb were theoretically investigated. The obtained results are in agreement with the experiment, confirming the electron-phonon coupling mechanism of superconductivity. We compare the superconducting parameters to those of all reported Heusler-type superconductors.

Superconductivity in High-Entropy Antimonide M1–xPtxSb (M = Equimolar Ru, Rh, Pd, and Ir)

“…The observed upper critical fields were relatively high but did not exceed the Pauli paramagnetic limit of 3.96 T. A coherence length ξ 0 of 160 Å was obtained from H c2 (0) GL , which is lower than that of other superconductors with similar T c values: T c = 1.32 K, μ 0 H c2 (0) = 0.09 T for PdSb; T c = 2.2 K, μ 0 H c2 (0) = 0.194 T, ξ 0 = 412 Å for MgPd 2 Sb; T c = 2.1 K, μ 0 H c2 (0) = 0.14 T, ξ 0 = 480 Å for BaIr 2 P 2 . , H c2 (0) tends to be relatively high in HEA superconductors. , The highly disordered arrangement of the TM atoms may be related to their short coherence lengths.…”

“…The heat capacity of the normal state just above T c was reproduced well by C / T ( T ) = γ + β T 2 , yielding γ = 2.85(2) mJ mol –1 K –2 and β = 0.346(3) mJ mol –1 K –4 by fitting the data. A Debye temperature (Θ D ) of 224 K was obtained from the β value; the obtained Θ D was comparable to those of other TM antimonides: Θ D = 212 K for RuSb, Θ D = 308 K for IrSb 3 , and Θ D = 250 K for MgPd 2 Sb . The comparable Θ D values indicate that neither significant softening nor hardening of the lattice vibrations occurred in the HE antimonides.…”

“…The comparable Θ D values indicate that neither significant softening nor hardening of the lattice vibrations occurred in the HE antimonides. The Sommerfeld constant γ was smaller than in the analogous antimony compounds: γ = 5.5 mJ mol –1 K –2 for RuSb, γ = 2.63 mJ mol –1 K –2 for PdSb, and γ = 4.9 mJ mol –1 K –2 for MgPd 2 Sb . The smaller γ values were likely due to the high degree of disorder at the TM sites, which reduced in the density of states (DOS) at the Fermi energy ( E F ).…”

“…A Debye temperature (Θ D ) of 224 K was obtained from the β value; 38 the obtained Θ D was comparable to those of other TM antimonides: Θ D = 212 K for RuSb, 39 Θ D = 308 K for IrSb 3 , 40 and Θ D = 250 K for MgPd 2 Sb. 41 The comparable Θ D values indicate that neither significant softening nor hardening of the lattice vibrations occurred in the HE antimonides. The Sommerfeld constant γ was smaller than in the analogous antimony compounds: γ = 5.5 mJ mol −1 K −2 for RuSb, 39 γ = 2.63 mJ mol −1 K −2 for PdSb, 26 and γ = 4.9 mJ mol −1 K −2 for MgPd 2 Sb.…”

“…The Sommerfeld constant γ was smaller than in the analogous antimony compounds: γ = 5.5 mJ mol −1 K −2 for RuSb, 39 γ = 2.63 mJ mol −1 K −2 for PdSb, 26 and γ = 4.9 mJ mol −1 K −2 for MgPd 2 Sb. 41 The smaller γ values were likely due to the high degree of disorder at the TM sites, which reduced in the density of states (DOS) at the Fermi energy (E F ). Using the obtained Sommerfeld constant to evaluate the jump in heat capacity, ΔC/(γT c ) = 1.56 was obtained, which was slightly larger than the value of 1.43 expected for conventional weakcoupling BCS superconductors.…”