Phase transitions and magnetic entropy change in Mn-rich Ni2MnGa alloys

Thermomagnetic and magnetocaloric (MC) properties of Ni2MnGa Heusler alloys are found to be very sensitive to small composition variations. It is shown that the temperature behavior of ac susceptibility mimics that of MC properties of the samples. The coincidence of magnetic and structural transformations is found for a Mn-rich composition. As in the case of Ni-rich alloys, the magnetocaloric effect is enhanced at the transitions co-occurrence. The increase of Mn content, with respect to the stoichiometric value, rapidly decreases anisotropy field and saturation magnetization.