Origin of magnetic interactions and their influence on the structural properties of Ni2MnGa and related compounds

Abstract

In this work, we perform first principles DFT calculations to investigate the interplay between magnetic and structural properties in Ni2MnGa. We demonstrate that the relative stability of austenite (cubic) and non-modulated martensite (tetragonal) phases depends critically on the magnetic interactions between Mn atoms. While standard approximate DFT functionals stabilize the latter phase, a more accurate treatment of electronic localization and magnetism, obtained with DFT+U, suppresses the non-modulated tetragonal structure for the stoichiometric compound, in better agreement with the experiments. We show that the Anderson impurity model, with Mn atoms treated as magnetic impurities, can explain this observation and that the fine balance between super-exchange RKKY type interactions mediated by Ni d and Ga p orbitals determines the equilibrium structure of the crystal. The Anderson model is also demonstrated to capture the effect of the number of valence electrons per unit cell on the structural properties, often used as an empirical parameter to tune the behavior of Ni2MnGa based alloys. Finally, we show that off-stoichiometric compositions with excess Mn promote transitions to a non-modulated tetragonal structure, in agreement with experiments.

16 pages, 25 figures

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Cited by in corpus (7)

• Hubbard-corrected DFT energy functionals: the LDA+U description of correlated systems
• Hubbard-corrected density functional perturbation theory with ultrasoft pseudopotentials
• Correlation in noncollinear antiferromagnetic $\alpha$-Mn
• Correlation effects on ground-state properties of ternary Heusler alloys: first-principles study
• Effect of L21 and XA ordering on phase stability, half-metallicity and magnetism of Co2FeAl Heusler Alloy: GGA and GGA+U approach
• Electronic structure beyond the generalized gradient approximation for Ni${}_2$MnGa
• Shear Deformation of Nonmodulated Ni${}_2$MnGa Martensite: An Ab Initio Study