Abstracts Category : Other

SUPERCONDUCTING PROPERTIES OF Zr1+XNi2-XGa AND Zr1-XNi2+XGaHEUSLER COMPOUNDS

by Saad Alzahrani

The superconducting and magnetic properties of aseries of Zr1+xNi2-xGa and Zr1-xNi2+xGa compounds have beeninvestigated by x-ray diffraction, scanning electron microscope,electrical resistivity, dc magnetization, and ac susceptibilitymeasurements. Van hove singularity, which refers to a high densityof states near the fermi energy level, are believed to causesuperconductivity in these materials. The electron concentration isless than 6.5 in Zr1+xNi2-xGa compounds while greater than 6.5 inZr1-xNi2+xGa compounds. While the parent compound, ZrNi2Ga,exhibited the cubic L21 Heusler structure, multiple non-cubicstructures of tetragonal and monoclinic phases formed in the dopedZr1+xNi2-xGa and Zr1-xNi2+xGa materials. For x > 0.3, theZr1+xNi2-xGa compounds show structural order of dominant monoclinicphase with a small presence of the tetragonal phase. On the otherhand, the Zr1-xNi2+xGa compounds show structural disorder of cubic,tetragonal, and monoclinic phases. For x = 0.3, all Zr1-xNi2+xGacompounds demonstrated superconducting behavior, but nosuperconductivity was observed in the Zr1+xNi2-xGa alloys for x> 0.2. The magnetization data revealed that all materials inboth the Zr1+xNi2-xGa and Zr1-xNi2+xGa series exhibited type-IIsuperconductivity. With increasing doping concentration x, theparamagnetic ordering was enhanced in both systems while thesuperconducting properties were found to weaken. The observationsare discussed considering the structural disorders in thesystems.Advisors/Committee Members: Khan, Mahmud (Advisor).