Observation of a Phase Transition at 55 K in Single-Crystal CaCu1.7As2

Abstract

We present the structural, magnetic, thermal and ab-plane electronic transport properties of single crystals of CaCu1.7As2 grown by the self-flux technique that were investigated by powder x-ray diffraction, magnetic susceptibility chi, isothermal magnetization M, specific heat Cp, and electrical resistivity rho measurements as a function of temperature T and magnetic field H. X-ray diffraction analysis of crushed crystals at room temperature confirm the collapsed tetragonal ThCr2Si2-type structure with \sim 15% vacancies on the Cu sites as previously reported, corresponding to the composition CaCu1.7As2. The chi(T) data are diamagnetic, anisotropic and nearly independent of T. The chi is larger in the ab-plane than along the c-axis, as also observed previously for SrCu2As2 and for pure and doped BaFe2As2. The Cp(T) and rho(T) data indicate metallic sp-band character. In contrast to the chi(T) and Cp(T) data that do not show any evidence for phase transitions below 300 K, the rho(T) data exhibit a sharp increase in slope on cooling below a temperature Tt = 54-56 K, depending on the crystal. The ρ(T) data show no hysteresis on warming and cooling through Tt and the transition appears to be second order. The phase transition may arise from spatial ordering of the vacancies on the Cu sublattice. The Tt is found to be independent of H for H \leq 8 T. A positive magnetoresistance is observed below Tt that increases with decreasing T and attains a value in H = 8.0 T of 8.7% at T = 1.8 K.

9 pages, 7 figures, 4 tables, 38 references; v2: Added discussion of Fe vacancies in AFe2Se2 compounds. Added new resistivity data for CaCu1.7As2 and new discussion of them; v3: minor changes, published version

References in corpus (15)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• Superconductivity at 22 K in Co-doped BaFe2As2 Crystals
• Superconductivity up to 37 K in (A1-xSrx)Fe2As2 with A=K and Cs
• To What Extent Iron-Pnictide New Superconductors Have Been Clarified: A Progress Report
• Pressure induced superconductivity in CaFe${}_2$As${}_2$
• Superconductivity up to 29 K in SrFe2As2 and BaFe2As2 at high pressures
• Anisotropy in the electrical resistivity and susceptibility of superconducting BaFe${}_2$As${}_2$ single crystals
• High-Temperature Superconductivity in Eu0.5K0.5Fe2As2
• Different resistivity response to spin density wave and superconductivity at 20 K in $C{a}_{1-x}N{a}_{x}F{e}_{2}A{s}_2$
• Structural transition and anisotropic properties of single crystalline SrFe2As2
• Structural, Thermal, Magnetic and Electronic Transport Properties of the LaNi2(Ge{1-x}P{x})2 System
• Crystal Growth and Physical Properties of SrCu2As2, SrCu2Sb2 and BaCu2Sb2
• Electronic properties of 3d transitional metal pnictides : A comparative study by optical spectroscopy
• Electronic structure of BaCu${}_2$As${}_2$ and SrCu${}_2$As${}_2$: sp-band metals
• Structural, Magnetic and Electronic Properties of the Iron-Chalcogenide A${}_x$Fe${}_{2-y}$Se${}_2$ (A=K, Cs, Rb, Tl and etc.) Superconductors

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