The Coefficient of Refrigeration Performance and Stress-Assisted Magnetocaloric Effect in Meta-Magnetic Shape Memory Alloys

Meta-magnetic shape memory alloys (MMSMAs) exhibit multi-physical couplings across a reversible first-order martensitic transition which leads to their potential applications in solid-state cooling, thermally or magnetically driven precision actuation, energy harvesting, and magnetic memory storage. Through their magneto-structural transitions and simultaneous transformation latent heat, MMSMAs are capable of the magnetocaloric effect (MCE) at two distinct operating temperatures (i.e., the critical martensitic transformation temperature and the ferromagnetic Curie point of either the austenite or martensite phase). In this study, the Refrigeration Capacity (RC) and Coefficient of Refrigeration Performance (CRP) in MMSMAs are shown to depend on the critical martensite transformation temperatures and, by extension, uniaxial mechanical stress. A loading sequence, namely the stress-assisted magnetic field-induced phase transformation (SAMFIT) is described, whereby mechanical stress and magnetic field are applied to an MMSMA specimen in sequence to effectively increase the thermal operating range and CRP for a single MMSMA composition.