Abstract
In this article, we studied the specific heat data of iron-based superconductors LaO1− x F x FeAs (x = 0.1) and SmO1− x F x FeAs (x = 0.13, 0.12, and 0.1). (i) The contribution of phonons in specific heat above Tc depends exponentially on temperature. (ii) The specific heat has different contributions, and they change differently at Tc . This change must be the effect of a physical function on heat capacity. Therefore, transition temperature is defined by thermal parameters. For LaO0.9F0.1FeAs and SmO0.87F0.13FeAs, a transition point was evaluated at 22.11 and 26.32 K, respectively. This is in close agreement with the midpoint transition temperatures obtained from dc resistivity and magnetization experiments, where the modified electronic heat capacity led to the approximate value of the transition point in two samples. The jump, ΔC/γT c, and the electronic and lattice heat capacity coefficients, γ and β, respectively, were evaluated.