Magnetocaloric Effect in Ni–Mn–Ga Alloys

Heusler alloys with nickel rich nominal composition Ni2+xMn1-xGa (x = 0.16 - 0.26) were prepared by arc-melting and subsequent homogenization by annealing. A large magnetic entropy change around room temperature was observed in the alloy where martensite-austenite structural and ferro-para magnetic transition temperatures almost coincide with each other. It also shows large hysteresis in the magnetization isothermals. A sharp peak in the specific heat versus temperature curve indicates a first-order transition at the temperature of large entropy change.