MgPd2Sb : A Mg-based Heusler-type superconductor

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.