d-d hybridization controlled large-volume-change martensitic phase transition in Ni-Mn-Ti-based all-d-metal Heusler compounds

Martensitic phase transition in all-d-metal Heusler compounds was investigated by using first principles calculations. The large change in volume during martensitic phase transition and its physical origin were revealed in representative compound Ni2MnTi. It was found that the enhanced d-d interatomic hybridization due to intrinsic volume shrinkage during martensitic phase transition led to significant increase in thermodynamic driving force and great improvement in the deformation ability. Their strong correlations induced large volume change during martensitic phase transition. The tetragonal martensitic phase in Ni2MnTi preferred the weaker magnetic state. Herein, it was proposed that a metamagnetic martensitic phase transition from cubic ferromagnetic phase to tetragonal ferrimagnetic phase with large volume change can be realized by tuning d-d interatomic hybridization level. The investigations indicate that careful control of interatomic hybridization level in Ni-Mn-Ti-based compounds can serve as an inherent tuning parameter to design and explore high-performance candidates as phase transition materials for solid-state refrigeration.