First-principles study of Zn-doping effects on phase stability and magnetic anisotropy of Ni-Mn-Ga alloys

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 T-M and Curie temperature T-C were predicted from calculated energy differences between austenite and nonmodulated martensite, Delta EA-NM, and energy differences between paramagnetic and ferromagnetic state, Delta EPM-FM. Doping upon the Ga-sublattice results in stabilization of martensitic phase which indicates the increase in T-M. T-C is affected only weakly or slightly decreases, because Delta EPM-FM of martensite does not change significantly with doping. The substitution of Mn atoms by Zn causes the decrease in both T-M and T-C. Comparing to Cu-doped Ni-Mn-Ga alloys, we predict that doping with Zn results in smaller decrease in T-C but also in smaller increase in T-M. 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 T-C can result in significant increase in both transformation temperatures without strong decrease of magnetic anisotropy.

Keywords

magnetic shape memory alloy, ab initio calculations, doping, phase stability, martensitic transformation, Curie temperature, magnetic anisotropy

Citation

Materials Research Express. 2020, vol. 7, issue 2, p. 026101--.
https://iopscience.iop.org/article/10.1088/2053-1591/ab6925

Document type

Peer-reviewed

Document version

Published version

Language of document

en

Document licence

Creative Commons Attribution 4.0 International
http://creativecommons.org/licenses/by/4.0/