Sign change in c-axis thermal expansion and lattice collapse by Ni substitution in Co1-xNixZr2 superconductors

Abstract

We investigated the structural, electronic, and superconducting properties of Co1-xNixZr2, in which c-axis thermal expansion is systematically controlled. At x (smaller than) 0.3, c-axis negative thermal expansion (NTE) was observed, and the thermal expansion constant αc approached zero with increasing x. At x = 0.4-0.6, zero thermal expansion was observed, and positive thermal expansion (PTE) appeared for x (greater than) 0.7. By analyzing the c/a ratio, we observed a possible collapsed transition in the tetragonal lattice at around x = 0.6-0.8. The lattice collapse results in c-axis PTE and the suppression of bulk superconductivity.

16 pages, 5 figures, 1 table, Supporting materials

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• Synthesis of high-entropy-alloy-type superconductors (Fe,Co,Ni,Rh,Ir)Zr2 with tunable transition temperature
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Cited by in corpus (5)

• Axis thermal expansion switching in transition-metal zirconides TrZr2 by tuning the c/a ratio
• Specific heat analyses on optical-phonon-derived uniaxial negative thermal expansion system $Tr$Zr${}_2$ ($Tr$ = Fe and Co${}_{1-x}$Ni${}_x$)
• Pressure-induced volumetric negative thermal expansion in CoZr2 superconductor
• Uniaxial negative thermal expansion in a tetragonal V3S-type superconductor IrZr3
• Superconducting properties and electronic structure of CuAl2-type transition-metal zirconide Fe1-xNixZr2