Superconducting properties of Zr-doped Ni$_{\mathrm{2}}$ZrGa$_{\mathrm{1-}}_{x}$Ge$_{x}$

ZrNi$_{\mathrm{2}}$Ga is a Heusler compound of AB$_{\mathrm{2}}$C formula that exhibits type-II superconductivity with a critical temperature of 2.9 K. The critical temperature of this compound has been attributed to its valence electron concentration of 6.75. It is interesting to investigate the effect of increased valence electron concentration on the critical temperature. In light of this, we have performed an experimental investigation on a series of Ni$_{\mathrm{2}}$ZrGa$_{\mathrm{1-}}_{x}$Ge$_{x}$ Heusler alloys by means of X-ray diffraction, magnetization, and electrical resistivity measurements. All alloys were found to primarily crystallize in the L2$_{\mathrm{1}}$ cubic structure at room temperature, with some secondary phases in samples with $x$ \textgreater 0.15. The magnetization and electrical resistivity measurements revealed that all samples exhibit type-II superconductivity despite the increase in structural disorder across the series, and that the critical temperature decreases with Ge content. The experimental results and conjectures as to the role of Ge in determining the superconducting properties will be discussed.