Influence of superelastic training and huge strains on field-induced martensitic variants reorientation in particulate Ni–Mn–Ga/silicone composite

Ni–Mn–Ga ferromagnetic shape memory alloys (FSMAs) are promising materials for actuator and transducer devices. Their intrinsic brittleness and high fabrication cost in the bulk form are issues to be solved. One of the solutions is a development of composites comprising these materials as a filler component whereby representing an emerging research field in the FSMAs. To address the improvement and stability challenges of the magnetic field-induced martensitic variant reorientation (MVR) characteristics of the particles in the previously elaborated ‘Ni–Mn–Ga single-crystalline particles/silicone rubber’ composites and to unveil new aspects of their functional behaviors, in the present work, we have investigated MVR characteristics as a function of compression cycling and under huge in-situ opposing contractions. It was found that after cycling with the 30% of compressive strain along the particle chains, the value of switching magnetic field needed to start MVR events was notably reduced, whereas it was almost intact when in-situ measured under the same compression level. In-situ measurements of the ‘magnetization versus magnetic field’ curves of the composite squeezed by 50% or 70% did not show MVR blocking. Instead, they revealed both a drastic decrease of the MVR switching field and narrowing of the MVR interval caused by the barreling effect. The results can be useful for the development of novel types of actuators and transducers.