A First-Principles Investigation of Phonon Softenings and Lattice Instabilities in the Shape-Memory System Ni${}_2$MnGa

Abstract

Ferromagnetic \nmg has unique magnetoelastic properties. These are investigated by detailed computational studies of the phonon dispersion curves for the non-modulated cubic \Ltw and tetragonal structures. For the \Ltw\ structure, a complete softening of the transverse acoustic mode has been found around the wave vector $\mathbf{q}=[1/3,1/3,0](2\pi /a)$. The softening of this \TA{2} phonon mode leads to the premartensitic modulated super-structure observed experimentally. Further phonon anomalies, related to other structural transformations in \nmg, have also been found and examined. These anomalies appear to be due to the coupling of particular acoustic phonon modes and optical modes derived from Ni.

4 pages, 4 figures

References in corpus (3)

• Premartensitic transition driven by magnetoelastic interaction in bcc ferromagnetic $N{i}_{2}MnGa$
• Magnetic shape-memory effects in La2-xSrxCuO4 crystals
• First-principles calculations of spin spirals in Ni2MnGa and Ni2MnAl

Cited by in corpus (27)

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• Magnetism in tetragonal manganese-rich Heusler compounds
• Martensitic transition, ferrimagnetism and Fermi surface nesting in Mn_2NiGa
• Modulations in martensitic Heusler alloys originate from nanotwin ordering
• Free energy calculation of mechanically unstable but dynamically stabilized bcc titanium
• Local Atomic Structure of Martensitic Ni${}_{2+x}$Mn${}_{1-x}$Ga: An EXAFS Study
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• Ordering tendencies and electronic properties in quaternary Heusler derivatives
• Observation of Phasons in Magnetic Shape Memory Alloy Ni2MnGa
• Ab initio prediction of stable nanotwin double layers and 4O structure in Ni${}_2$MnGa
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• Lattice dynamics and phonon softening in Ni-Mn-Al Heusler alloys
• Interplay of phase sequence and electronic structure in the modulated martensites of Mn${}_2$NiGa from first-principles
• Magnetic phase diagram of the semi-Heusler alloys from first-principles
• Electronic structure beyond the generalized gradient approximation for Ni${}_2$MnGa
• Phonon-assisted diffusion in bcc phase of titanium and zirconium from first-principles
• First-principles study of the lattice instabilities in Mn${}_2$Ni{\it X} ({\it X}= Al, Ga, In, Sn) magnetic shape memory alloys
• Coherent phonon dynamics at the martensitic phase transition of Ni_2MnGa
• Predicted superconductivity of Ni2VAl and pressure dependence of superconductivity in Ni2NbX (X = Al, Ga and Sn) and Ni2VAl
• Ab-initio study of structure and dynamics properties of crystalline ice
• Broken Dynamic Symmetry and Phase Transition Precursor
• Crystal Structures of Ni${}_2$MnGa from Density Functional Calculations
• Stress-induced Martensitic transformation in epitaxial Ni-Mn-Ga thin films and its correlation to optical and magneto-optical properties