The varying nature of the martensitic phase transition and associated entropy changes in a Co and Cr doped pseudo-ternary Heusler alloy system

Abstract

We have investigated the magnetostructural phase transitions and the associated entropy changes in a system of three Heusler alloys, namely: Ni2Mn0.55Cr0.45Ga, Ni2Mn0.55Co0.10Cr0.35Ga, and Ni2.15Mn0.75Cr0.1Ga. All three alloys exhibited first-order martensitic phase transition. An inter-martensitic phase transition raised the magnetic and structural phase transition temperatures, and partially decoupled the said transitions. Furthermore, field magnetization measurements demonstrated that a significant reduction in magnetic hysteresis is achieved in the Ni2Mn0.55Co0.10Cr0.35Ga compound, resulting in improved effective refrigerant capacity values. The largest magnetic entropy change of −23.5 J/kg K and refrigeration capacity of 97.7 J/kg were observed in Ni2.15Mn0.75Cr0.1Ga. This observation of mitigated deficiencies in materials experiencing a first-order phase transition is relevant towards their application in magnetic refrigeration.