The magneto-thermal properties of Ni-deficient Mn0.5+xFe0.5Ni1-xSi0.95Al0.05 intermetallic System

The thermal response of a magnetic material to an external magnetic field is often described as the magnetocaloric effect (MCE). The magnetic entropy change of a material is one of the parameters that quantifies MCE. The intermetallic compound Mn_0.5Fe_0.5NiSi_0.95Al_0.05 exhibits a first order magnetostructural phase transition near 315 K. In the vicinity of the phase transition, a large magnetic entropy change of -15 J/kg K for a field change of 20 kOe is observed. This property along with the fact that the material consist of inexpensive, nontoxic, and non-rare earth elements, is considered a viable candidate for use in the magnetic refrigeration technology. A major issue that need to be solved in this material is a large thermal hysteresis that accompanies the first order phase transition. Therefore, it is interesting to explore possible ways to suppress the thermal hysteresis in Mn_0.5Fe_0.5NiSi_0.95Al_0.05 and related compounds. Here, we will present an experimental study on the effects of substituting Mn with Ni on the magnetic and magnetocaloric properties of a series of Mn_0.5+xFe_0.5Ni_1-xSi_0.95Al_0.05 intermetallic compounds. A detailed discussion on the structural, magnetic and magnetocaloric properties of the materials will be presented.