Magnetic and magnetocaloric properties of Ni47Mn40Sn13−xZnx alloys: Direct measurements and first-principles calculations

In the present study, the martensitic transformation (MT) and magnetic properties exhibited by the Ni-Mn-Sn Heusle-type magnetic shape memory alloys (MSMAs) doped with Zn have been investigated experimentally and theoretically. The inverse magnetocaloric effect (MCE) in ${\text{Ni}}_{47}{\text{Mn}}_{40}{\text{Sn}}_{13\ensuremath{-}x}{\text{Zn}}_{x}$ (x = 0, 1) was studied by direct measurements of the adiabatic temperature change, $\mathrm{\ensuremath{\Delta}}{T}_{\text{ad}}$, in pulsed magnetic fields of 5, 10, and 20 T. The Zn doping of the Ni-Mn-Sn alloy led to a striking enhancement of the value of $\mathrm{\ensuremath{\Delta}}{T}_{\text{ad}}$, e.g., from --2.5 for undoped to --11 K for Zn-doped alloys under a magnetic field amplitude of 20 T. The first-principles calculations were used to understand the origin of Zn-doping influence on MT, magnetic, and magnetocaloric properties. Particularly, the crystal structure and magnetic ordering influenced by the site occupancy in the undoped and Zn-doped alloys were analyzed. The results show that, whereas the usual transition metal elements with more valence electrons tend to enter the Ni sites, Zn atom prefers to occupy the Sn sublattice. The underlying physics of the drastic enhancement of MCE by Zn doping is discussed in terms of a partial disorder in the occupation sites of Zn atoms.