Anomalous thermal expansion in a CuAl2-type superconductor CoZr2

Abstract

In this work, we show that the CuAl2-type superconductor CoZr2 and alloyed systems exhibit anomalous thermal expansion in a wide temperature range. We performed neutron powder diffraction and X-ray powder diffraction on CoZr2 and observed remarkably anisotropic thermal expansion with a c-axis negative thermal expansion constant of αc < -15 μK-1 in a wide temperature range of T = 50-573 K. With decreasing temperature, the lattice constant a decreases, while the lattice constant c continuously increases in CoZr2. The origin of the anisotropic shrinkage/expansion of the a-axis/c-axis by cooling is explained by the small change in the Co-Zr bond and the systematic decrease in the Zr-Co-Zr angle. Similar thermal expansion was observed in alloyed systems, (Fe,Co,Ni)Zr2 and (Fe,Co,Ni,Rh,Ir)Zr2, which suggests that the phenomenon is common feature in the TrZr2 system. We propose that zero-thermal expansion metals would be achieved by optimizing the contrasting thermal expansion of a-axis and c-axis in TrZr2.

arXiv comment17 pages, 5 figures, supplementary data

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• Magnetic Ordering and Negative Thermal Expansion in PrFeAsO
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Cited by in corpus (7)

• Sign change in c-axis thermal expansion and lattice collapse by Ni substitution in Co1-xNixZr2 superconductors
• Axis thermal expansion switching in transition-metal zirconides TrZr2 by tuning the c/a ratio
• Uniaxial negative thermal expansion in an orthorhombic superconductor CoZr3
• Uniaxial negative thermal expansion in a tetragonal V3S-type superconductor IrZr3
• Pressure-induced volumetric negative thermal expansion in CoZr2 superconductor
• Specific heat analyses on optical-phonon-derived uniaxial negative thermal expansion system $Tr$Zr${}_2$ ($Tr$ = Fe and Co${}_{1-x}$Ni${}_x$)
• Superconducting properties and electronic structure of CuAl2-type transition-metal zirconide Fe1-xNixZr2