Giant Magnetic-Field-Induced Strain in Ni2MnGa-based polycrystal

TL;DR

This study demonstrates that by substituting elements in Ni2MnGa alloys, large, reproducible magnetic-field-induced strains near room temperature can be achieved with relatively low magnetic fields, advancing practical applications.

Contribution

It shows that substitution on the Mn site can tune magnetostructural transitions to near room temperature, enabling large strains at low magnetic fields in polycrystalline Ni2MnGa alloys.

Findings

Achieved strains up to 2.6% at 8 T near 305 K.

Induced strains as low as 1.6% at 0.25 T near 297.4 K.

Demonstrated potential for scalable, low-cost shape memory applications.

Abstract

Ferromagnetic Ni2MnGa-based alloys play an important role in technological fields, such as smart actuators, magnetic refrigeration and robotics. The possibility of obtaining large non-contact deformation induced by an external perturbation is one of its key strengths for applications. However, the search for materials with low cost, practical fabrication procedures and large signal output under small perturbing fields still poses challenges. In the present study we demonstrate that by judicial choice of substitution on the Mn site, an abrupt magnetostructural transition from a paramagnetic austenite phase to a ferromagnetic martensite one can be tuned to close to room temperature achieving large and reproducible strains. The required magnetic field to induce the strain varies from small values, as low as 0.25 T for 297.4 K and 1.6% of strain, to 8 T for 305 K and 2.6% of strain. Our findings point to encouraging possibilities for application of shape memory alloys in relatively inexpensive, scalable polycrystalline materials.