Lack of superconductivity in the phase diagram of single-crystalline Eu(Fe1-xCox)(2)As-2 grown by transition metal arsenide flux
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The interplay of magnetism and superconductivity (SC) has been a focus of interest in condensed matter physics for decades. EuF e 2 A s 2 has been identified as a potential platform to investigate interactions between structural, magnetic, and electronic effects as well as the coexistence of magnetism and SC with similar transition temperatures. However, there are obvious inconsistencies in the reported phase diagrams of Eu ( F e 1 − x C o x ) 2 A s 2 crystals grown by different methods. For transition metal arsenide (TMA)-flux-grown crystals, even the existence of SC is uncertain. Here we reexamine the phase diagram of single-crystalline Eu ( F e 1 − x C o x ) 2 A s 2 grown by TMA flux. We found that the lattice parameter c shrinks linearly with Co doping, almost twice as fast as that of the tin-flux-grown crystals. With Co doping, the spin-density-wave (SDW) order of the Fe sublattice is quickly suppressed, being detected only up to x = 0.08 . The magnetic ordering temperature of the E u 2 + sublattice ( T Eu ) shows a systematic evolution with Co doping, first going down and reaching a minimum at x = 0.08 , then increasing continuously up to x = 0.24 . Over the whole composition range investigated, no signature of SC is observed above 1.8 K.