Role of covalent hybridization in martensitic structure and magnetic properties of shape memory alloys: the case of Ni50Mn5+xGa35-xCu10

TL;DR

This study explores how covalent hybridization influences the martensitic structure and magnetic properties of Ni50Mn5+xGa35-xCu10 shape memory alloys, revealing a critical composition at Ga(%)=25 where properties peak.

Contribution

It demonstrates that controlling main-group atom concentration in Heusler alloys tunes their structural and magnetic properties via covalent hybridization effects.

Findings

Lattice distortion varies monotonously with Mn substitution and shows a kink at Ga(%)=25.

Magnetic moment and Curie temperature peak at Ga(%)=25.

Covalent hybridization strength correlates with structural and magnetic changes.

Abstract

We have investigated the impact of covalent hybridization on martensitic structure and magnetic properties of Ni50Mn5+xGa35-xCu10 shape memory alloys. We found that the lattice distortion ((c-a)/a) of L10 martensite monotonously changes with the substitution of Mn for Ga atoms and shows a kink behavior at Ga(at.%)= 25 due to the weakened covalent effect between main-group and transition-metal atoms. Moreover, owing to the competition between covalence hybridization and magnetic ordering of introduced Mn atoms, the molecular magnetic moment and Curie temperature coincidently show maximums at Ga(at.%)=25 as well. These behaviors are closely associated with corresponding changes of the strength of covalent hybridization. The results therefore suggest that careful control of the concentration of main-group atoms in Heusler alloys can serve as an additional general tuning parameter for searching new multifunctional materials.