<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Mg</mml:mi><mml:msub><mml:mi>Pd</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi>Sb</mml:mi></mml:mrow></mml:math>: A Mg-based Heusler-type superconductor
Michał J. Winiarski, Gabriel Kuderowicz, Karolina Górnicka, Leszek Sławomir Litzbarski, Kamila Stolecka, Bartłomiej Wiendlocha, R. J. Cava, Tomasz Klimczuk
Abstract
We report the synthesis and physical properties of a full Heusler compound, $\mathrm{Mg}{\mathrm{Pd}}_{2}\mathrm{Sb}$, which we found to show superconductivity below ${T}_{c}=2.2\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. $\mathrm{Mg}{\mathrm{Pd}}_{2}\mathrm{Sb}$ was obtained by a two-step solid-state reaction method and its purity and cubic crystal structure [$Fm\text{\ensuremath{-}}3m, a=6.4523(1)\phantom{\rule{0.16em}{0ex}}\AA{}$] 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 $\mathrm{Mg}{\mathrm{Pd}}_{2}\mathrm{Sb}$ is a type-II, weak coupling superconductor (${\ensuremath{\lambda}}_{e\text{\ensuremath{-}}p}=0.53$). The observed pressure dependence of ${T}_{c}$ ($\mathrm{\ensuremath{\Delta}}{T}_{c}/p\ensuremath{\approx}--0.23\phantom{\rule{0.16em}{0ex}}\mathrm{K}/\mathrm{GPa}$) is one of the strongest reported for a superconducting Heusler compound. The electronic structure, phonons, and electron-phonon coupling in $\mathrm{Mg}{\mathrm{Pd}}_{2}\mathrm{Sb}$ 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.