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Abstract:
We present a calorimetric study on single crystals of Ca(Fe 1â x Co x ) 2 As 2 ( x = 0, 0.032, 0.051, 0.056, 0.063, and 0.146). The combined first order spin-density wave/structural transition occurs in the parent CaFe 2 As 2 compound at 168 K and gradually shifts to lower temperature for low doping levels ( x = 0.032 and x = 0.051). It is completely suppressed upon higher doping x ⥠0.056. Simultaneously, superconductivity appears at lower temperature with a transition temperature around T c ~ 14.1 K for Ca(Fe 0.937 Co 0.063 ) 2 As 2 . The phase diagram of Ca(Fe 0.937 Co 0.063 ) 2 As 2 has been derived and the upper critical field is found to be μ 0 H ( c ) 2 = 11.5 T and μ 0 H (ab) c 2 = 19.4 T for the c and ab directions, respectively.
