Switchable Ni–Mn–Ga Heusler nanocrystals

We examined bulklike Heusler nanocrystals using real-space pseudopotentials constructed within density functional theory. The nanocrystals were made of various compositions of Ni–Mn–Ga in the size range from 15 up to 169 atoms. Among these compositions, the closest to the stoichiometric $Ni2MnGa$ were found to be the most stable. The Ni-based nanocrystals retained a tendency for tetragonal distortion, which is inherited from the bulk properties. Surface effects suppress the tetragonal structure in the smaller Ni-based nanocrystals, while bigger nanocrystals develop a bulklike tetragonal distortion. We suggest the possibility of switchable Ni–Mn–Ga nanocrystals, which could be utilized for magnetic nanoshape-memory applications.