Peltier cell calorimetry “as an option” for commonplace cryostats: Application to the case of MnFe(P,Si,B) magnetocaloric materials

Abstract

Peltier cell calorimetry is a powerful technique to record both the heat capacity and the latent heat, yet its availability is limited as it often requires homemade dedicated cryostats. Here, we describe the development of a Peltier cell differential scanning calorimeter facilitating the accessibility to the technique, since it is designed “as an option” for commonplace commercial cryostats equipped with high magnetic fields. This yields an apparatus well suited to detailed studies of magnetic transitions in general and of first-order magnetic transitions in particular. For magnetocaloric materials, our system can also be used to measure directly the isothermal entropy change ΔS induced by a magnetic field change; it even allows separating the cyclic (reversible) effect due to successive magnetization/demagnetization, which is the one relevant for applications, from the total magnetocaloric effect. To illustrate the versatility of this system, a thorough study of the ferromagnetic first-order transition of MnFe_0.95P_0.585Si_0.34B_0.075 is carried out. An exceptionally large cyclic entropy change at an intermediate field is observed in this compound, ΔS_cyclic = 13.2 J kg⁻¹ K⁻¹ for µ₀ΔH = 1 T. This confirms that MnFe(P,Si,B) shows one of the most promising giant magnetocaloric effects to be used in emergent green technologies such as magnetocaloric cooling, heating or thermomagnetic waste heat recovery.