Work

Sub-nanosecond structural dynamics of the martensitic transformation in Ni-Mn-Ga

Year: 2026

Type: article

Abstract: Martensitic transformations drive many emerging applications, ranging from actuation and mechanocaloric refrigeration to thermoelastic energy harvesting. All these applications benefit from faster transformations. However, systematic investigations of the fast dynamics and fundamental speed limits of martensitic transformations are scarce. Especially for fast transformations, the temperature evolution throughout the transformation is not measured. Here, we present a time-resolved X-ray diffraction study of a fs laser-induced martensitic transformation in a Ni-Mn-Ga-based epitaxial film. We observe the transformation from martensite to austenite within about 90 ps, an upper limit set by the duration of the synchrotron probe pulse, so the transformation may occur even faster. Furthermore, a full transformation cycle can be finished within 5 ns, which is the fastest value reported so far. Measurements and calculations of the temperature evolution allow us to analyse the influence of temperature on transformation time. By time-resolved strain measurements, we demonstrate that in addition to temperature, stress must be considered as a competing influence on the martensitic transformation. Our experimental findings are extended to the ps time scale through molecular dynamics simulations using machine-learned force fields trained on density functional theory calculations. These simulations reveal that the large lattice distortion during a martensitic transformation necessitates the collective displacement of many atoms, which is the key factor limiting the transformation speed.

Source: Communications Materials

DOI: 10.1038/s43246-026-01317-4