The effect of TM doping on the superconducting properties of ZrNi2-xTMxGa (TM = Cu, Co) Heusler compounds.

We have explored the structural and superconducting properties of ZrNi2-xTMxGa (TM = Cu, Co) Heusler compounds via x-ray diffraction, scanning electron mi croscopy, electrical resistivity, dc magnetization and ac susceptibility measurements. All samples crystallized in the cubic L21 structure at room temperature. For <italic>x</italic> ≤ 0.25, all the ZrNi2-<italic>x</italic>Cu<italic>x</italic>Ga compounds showed superconducting properties and a decrease in <italic>T</italic>C with increasing Cu concentration. The dc magnetization data suggested type-II superconductivity for all the Cu-doped compounds. Contrary to the ZrNi2-<italic>x</italic>Cu<italic>x</italic>Ga compounds, no superconductivity was observed in the ZrNi2-<italic>x</italic>Co<italic>x</italic>Ga compounds. Substitution of Ni by a small concentration of Co destroyed superconductivity in the Co-doped compounds. The experimental results are discussed and possible explanations are provided. [ABSTRACT FROM AUTHOR]