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On the evaluation of specific heat from thermoelectric power



Thermoelectric power (TEP) measurement have been performed in the temperature range of 77–300 K for polycrystalline RFeAsO (R = Ce, Pr, Nd, and Sm) compounds. These compounds show sharp change in the TEP, SS (T),with an inflexion point resulting a peak in dSS (T)/dT. This peak temperature is slightly above the reported spin-density-wave (SDW) type magnetic ordering and slightly below the structural transition. The analysis of the reported data on single crystal suggest that this peak in polycrystals is resultant of two well defined, closely separated peaks at the above two temperatures. An attempt has been made to extract the excess entropy around these temperatures from SS (T) data using the simple formula developed by Tang et al. while analyzing the TEP data of itinerant ferromagnetic Ni [Phys. Rev. Lett. 27, 593 (1971)]. The present work focuses on the limitation of universal applicability of Tang et al.’s formulation in any arbitrary magnetic system.