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Phase diagram of iron-arsenide superconductors Ca(Fe1-xCox)2As2 (0 ≤ x ≤ 0.2)

Surjeet Singh - Indian Institute of Science Education and Research, Pune

We studied Ca(Fe1-xCox)2As2 single crystals obtained using high-temperature solution method. Pristine CaFe2As2 shows a combined spin-density-wave and structural transition near T = 166 K which gradually shifts to lower temperatures and splits with increasing Co-doping. Both transitions terminate abruptly at a critical Co-concentration of xc = 0.075. For x ≥ 0.05, superconductivity appears at low temperatures with a maximum transition temperature TC of around 20 K. The superconducting volume fraction increases with Co concentration up to x = 0.09 followed by a gradual decrease with further increase of the doping level. The electronic phase diagram of Ca(Fe1-xCox)2As2 (0 ≤ x ≤ 0.2) series is constructed from the magnetization and electric resistivity data. We show that the low-temperature superconducting properties of Co-doped CaFe2As2 differ considerably from those of BaFe2As2 reported previously. These differences are related to the extreme pressure sensitivity of CaFe2As2 relative to its Ba counterpart.


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