Temperature and magnetic field dependence of the heat capacity in itinerant electron ferromagnets

Based on the spin fluctuation mechanism we have succeeded in deriving formulae for the magnetic entropy and the specific heat of itinerant electron ferromagnets that cover the wide range of the temperature and the external field strength. We show that it is necessary to include an extra term into the free energy for a thermodynamically consistent treatment. We are able to predict several new features on the temperature and the external field dependence, an extra enhancement of the T-linear coefficient at low temperature and the presence of a critical peak anomaly of the specific heat, for instance. They result from terms proportional to the second-order temperature derivative of the spontaneous magnetization. The presence of the terms is connected with the Maxwell relation of thermodynamics.