Phase transitions and the magnetocaloric effect in Mn rich Ni–Mn–Ga Heusler alloys

In Mn rich polycrystalline Heusler alloys, Ni50Mn25+−xGa25−x, prepared by Arc melting, it is found that the structural/first-order magnetic transition temperature Tm increases as the Mn content increases. The Curie temperature Tc is higher than that of Ni rich alloys (Ni50+xMn25−xGa25 ) of the same series, and is less affected by composition x. Magnetic entropy change of |ΔSM| also increases as Mn content increases, while behaviour of the field dependence of ΔSM is similar to that of single crystal Ni52.6Mn23.1Ga24.3.