First-principles study of Zn-doping effects on phase stability and magnetic anisotropy of Ni-Mn-Ga alloys
Abstract
The effect of Zn doping on Ni-Mn-Ga magnetic shape memory alloy was studied by the first-principles calculations using exact muffin-tin orbital method in combination with the coherent-potential approximation and projector augmented-wave method. Trends in martensitic transformation temperature TM and Curie temperature TC were predicted from calculated energy differences between austenite and nonmodulated martensite, ΔEA-NM, and energy differences between paramagnetic and ferromagnetic state, ΔEPM-FM. Doping upon the Ga-sublattice results in stabilization of martensitic phase which indicates the increase in TM. TC is affected only weakly or slightly decreases, because ΔEPM-FM of martensite does not change significantly with doping. The substitution of Mn atoms by Zn causes the decrease in both TM and TC. Comparing to Cu-doped Ni-Mn-Ga alloys, we predict that doping with Zn results in smaller decrease in TC but also in smaller increase in TM. Moreover, Cu doping upon the Ga-sublattice strongly decreases the magnetic anisotropy energy of martensite, whereas such strong effect was not observed for Zn doping. Based on the calculations of Zn-doped Ni-Mn-Ga alloys we suggest that simultaneous doping with Zn and an element increasing TC can result in significant increase in both transformation temperatures without strong decrease of magnetic anisotropy.
- Publication:
-
Materials Research Express
- Pub Date:
- February 2020
- DOI:
- 10.1088/2053-1591/ab6925
- Bibcode:
- 2020MRE.....7b6101J
- Keywords:
-
- magnetic shape memory alloy;
- ab initio calculations;
- doping;
- phase stability;
- martensitic transformation;
- Curie temperature;
- magnetic anisotropy