A physical insight into magnetocaloric materials by calorimetry in magnetic field

In this paper we discuss the determination of the s(Ha,T) entropy constitutive relation of magnetocaloric materials by means of heat flux calorimetry. In particular we discuss a method to account for the temperature lag in scanning experiments. We show as examples Gd and hydrogenated La(Fe-Mn-Si)13-H (without hysteresis) and La-(Fe-Co-Si)13 and the Heusler Ni-Mn-Co-Sn (with hysteresis). The resulting magnetocaloric properties, i.e. the specific heat capacity as a function of the magnetic field and the magnetic field induced entropy change, are interpreted and discussed in terms of the ferromagnetic, electronic and structural contributions to the free energy and the entropy.