Jump in specific heat at the superconducting transition temperature in Ba(Fe1-xCox)2As2 and Ba(Fe1-xNix)2As2 single crystals

We present detailed heat capacity measurements for Ba(Fe1-xCox)(2)As-2 and Ba(Fe1-xNix)(2)As-2 single crystals in the vicinity of the superconducting transitions. The specific-heat jump at the superconducting transition temperature (T-c), Delta C-p/T-c, changes by a factor of similar to 10 across these series. The Delta C-p/T-c vs Tc data of this work [together with the literature data for Ba(Fe0.939Co0.061)(2)As-2, (Ba0.55K0.45(Fe2As2, and (Ba0.6K0.4)Fe2As2] scale well to a single log-log plot over two orders of magnitude in Delta C-p/T-c and over about an order of magnitude in T-c, giving Delta C-p/T-c proportional to T-c(2).