Pd₂ MnGa Metamagnetic Shape Memory Alloy with Small Energy Loss

Metamagnetic shape memory alloys (MMSMAs) are attractive functional materials owing to their unique properties such as magnetostrain, magnetoresistance, and the magnetocaloric effect caused by magnetic-field-induced transitions. However, the energy loss during the martensitic transformation, that is, the dissipation energy, E_dis , is sometimes large for these alloys, which limits their applications. In this paper, a new Pd₂ MnGa Heusler-type MMSMA with an extremely small E_dis and hysteresis is reported. The microstructures, crystal structures, magnetic properties, martensitic transformations, and magnetic-field-induced strain of aged Pd₂ MnGa alloys are investigated. A martensitic transformation from L2₁ to 10M structures is seen at 127.4 K with a small thermal hysteresis of 1.3 K. The reverse martensitic transformation is induced by applying a magnetic field with a small E_dis (= 0.3 J mol^-1 only) and a small magnetic-field hysteresis (= 7 kOe) at 120 K. The low values of E_dis and the hysteresis may be attributed to good lattice compatibility in the martensitic transformation. A large magnetic-field-induced strain of 0.26% is recorded, indicating the proposed MMSMA's potential as an actuator. The Pd₂ MnGa alloy with low values of E_dis and hysteresis may enable new possibilities for high-efficiency MMSMAs.