Wednesday, December 5, 2012

1212.0302 (G. J. Li et al.)

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

G. J. Li, E. K. Liu, H. G. Zhang, Y. J. Zhang, G. Z Xu, H. Z. Luo, H. W. Zhang, W. H. Wang, G. H. Wu
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.
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