Magnetocaloric effect across first order transformations of energy conversion materials

The Magnetocaloric Effect is a promising phenomenon which supports the development of innovative refrigerators and heat pumps which will be environmentally friendly and characterized by higher efficiency if compared to actual technologies. The aim of this work is the study this effect across first order magneto-structural martensitic transformations of NiMnGa-based alloys. The possibility to ''tune'' the properties of this phase transition by suitably controlling the material composition makes them very attractive. The aim of this work is to study such transformations to understand the real applicative potential of these systems. Three different experimental approaches are compared: magnetic characterization, the direct measurement of the temperature change induced by the applied magnetic field and a in-field Differential Scanning Calorimeter which allows to study the transformation latent heat and the specific heat at different applied magnetic fields. The adiabatic temperature change probe and the DSC are purposely realized for this aim. Moreover a new experimental setup is presented to analyze the material MCE while it is stressed by magnetization and demagnetization cycles in nearly operative conditions.