Influence of atomic order on [110] phonon softening [4] and displacive phase transition in Invar alloys

Kästner, J.; Petry, W.; Shapiro, S. M.; Zheludev, A.; Neuhaus, J.; Roessel, Th.; Wassermann, E.F.; Bach, H.

doi:10.1007/s100510050896

Cited by 22 publications

(31 citation statements)

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“…A strong anomalous softening of the TA 1 branch is a widely discussed observation from neutron diffraction experiments on ordered Fe 3 Pt. 21,24,27,28 With decreasing temperature starting from the paramagnetic phase, the TA 1 mode becomes increasingly softer at the M-point, finally reaching phonon energies as low as 3 meV for T = 12 K. The microscopic nature of the corresponding displacements will be discussed in the following section. An incomplete softening of the TA 1 branch with anomalous temperature dependence is also found for the disordered alloys.…”

Section: A Phonon Dispersion Relationsmentioning

confidence: 94%

“…Therefore the term antiferrodistortive transformation has been has been coined for the condensation of the unstable phonon mode. 27 The displacements can be inferred from the corresponding eigenvectors and are sketched in Fig. 7.…”

Section: 9697mentioning

confidence: 99%

“…This indirect procedure often leaves room for ambiguities and has lead to a controversy about the nature of the unstable mode in the past. 24,27 A more direct approach is to monitor the variation of the total energy as a function of the displacement according to the (frozen) phonon modes. This can be realized in a straight forward manner within a density functional theory approach.…”

Section: 9697mentioning

confidence: 99%

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Lattice dynamics and structural stability of orderedFe3Ni,Fe3Pdand
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We investigate the binding surface along the Bain path and phonon dispersion relations for the cubic phase of the ferromagnetic binary alloys Fe3X (X = Ni, Pd, Pt) for L12 and D022 ordered phases from first principles by means of density functional theory. The phonon dispersion relations exhibit a softening of the transverse acoustic mode at the M-point in the L12-phase in accordance with experiments for ordered Fe3Pt. This instability can be associated with a rotational movement of the Fe-atoms around the Ni-group element in the neighboring layers and is accompanied by an extensive reconstruction of the Fermi surface. In addition, we find an incomplete softening in [111] direction which is strongest for Fe3Ni. We conclude that besides the valence electron density also the specific Fe-content and the masses of the alloying partners should be considered as parameters for the design of Fe-based functional magentic materials.

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Section: A Phonon Dispersion Relationsmentioning

confidence: 94%

Section: 9697mentioning

confidence: 99%

Section: 9697mentioning

confidence: 99%

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Lattice dynamics and structural stability of orderedFe3Ni,Fe3Pdand
Gruner
¹
,
Adeagbo
²
,
Zayak
³

et al. 2010
Phys. Rev. B

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“…50,51 In this case, for the ordered Fe 3 Pt MSMA, a strong anomalous softening of the TA 1 branch in ͓110͔ direction is found at the zone boundary, which disappears in the disordered case in favor of a smeared out anomaly much closer to the ⌫ point. [52][53][54][55] Thus, the type and degree of disorder of a Co-Ni-Ga alloy, which is controlled experimentally by the annealing conditions, should be considered very important for the martensitic transformation and the ͑magnetic͒ shape-memory properties of the sample.…”

Section: Systemmentioning

confidence: 99%

Electronic structure and lattice dynamics of the magnetic shape-memory alloyCo2NiGa

et al. 2010

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In addition to the prototypical Ni-Mn-based Heusler alloys, the Co-Ni-Ga systems have recently been suggested as another prospective materials class for magnetic shape-memory applications. We provide a characterization of the dynamical properties of this material and their relation to the electronic structure within a combined experimental and theoretical approach. This relies on inelastic neutron scattering to obtain the phonon dispersion while first-principles calculations provide the link between dynamical properties and electronic structure. In contrast to Ni 2 MnGa, where the softening of the TA 2 phonon branch is related to Fermi-surface nesting, our results reveal that the respective anomalies are absent in Co-Ni-Ga, in the phonon dispersions as well as in the electronic structure. Keywords Materials Science and Engineering Disciplines Condensed Matter Physics | Materials Science and Engineering CommentsThis article is from Physical Review B 82 (2010) In addition to the prototypical Ni-Mn-based Heusler alloys, the Co-Ni-Ga systems have recently been suggested as another prospective materials class for magnetic shape-memory applications. We provide a characterization of the dynamical properties of this material and their relation to the electronic structure within a combined experimental and theoretical approach. This relies on inelastic neutron scattering to obtain the phonon dispersion while first-principles calculations provide the link between dynamical properties and electronic structure. In contrast to Ni 2 MnGa, where the softening of the TA 2 phonon branch is related to Fermisurface nesting, our results reveal that the respective anomalies are absent in Co-Ni-Ga, in the phonon dispersions as well as in the electronic structure.

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“…The elastic properties of Fe-Pt alloys were also examined by constructing phonon dispersion curves [22][23][24]. Tajima et al [22] reported that [110] TA 1 mode of an ordered Fe-27.8Pt (at %) alloy exhibits significant softening near the Γ-point (center of the Brillourin zone) with decreasing temperature.…”

Section: Introductionmentioning

confidence: 99%

Lattice Softening in Fe3Pt Exhibiting Three Types of Martensitic Transformations

Fukuda

Kakeshita

2017

Metals

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Abstract:We have investigated the relation between the softening of elastic constants and martensitic transformation in Fe 3 Pt, which exhibits various kinds of martensitic transformation depending on its long-range order parameter S. The martensite phases of the examined alloys are BCT (S = 0.57), FCT1 (S = 0.75, c/a < 1) and FCT2 (S = 0.88, c/a > 1). The elastic constants C and C 44 of these alloys decrease almost linearly with decreasing temperature. Although the temperature coefficient of C decreases as S increases, C at the transformation temperature is the smallest in the alloy with S = 0.75, which transforms to FCT1. This result implies that softening is most strongly related to the formation of the FCT1 martensite with tetragonality c/a < 1 among the three martensites.

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Influence of atomic order on [110] phonon softening [4] and displacive phase transition in Invar alloys

Cited by 22 publications

References 0 publications

Lattice dynamics and structural stability of orderedFe3Ni,Fe3Pdand
Gruner
¹
,
Adeagbo
²
,
Zayak
³

et al. 2010
Phys. Rev. B

Lattice dynamics and structural stability of orderedFe3Ni,Fe3Pdand
Gruner
¹
,
Adeagbo
²
,
Zayak
³

et al. 2010
Phys. Rev. B

Electronic structure and lattice dynamics of the magnetic shape-memory alloyCo2NiGa

Lattice Softening in Fe3Pt Exhibiting Three Types of Martensitic Transformations

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Influence of atomic order on [110] phonon softening [4] and displacive phase transition in Invar alloys

Cited by 22 publications

References 0 publications

Lattice dynamics and structural stability of orderedFe3Ni,Fe3PdandGruner1, Adeagbo2, Zayak3 et al. 2010Phys. Rev. B

Lattice dynamics and structural stability of orderedFe3Ni,Fe3PdandGruner1, Adeagbo2, Zayak3 et al. 2010Phys. Rev. B

Electronic structure and lattice dynamics of the magnetic shape-memory alloyCo2NiGa

Lattice Softening in Fe3Pt Exhibiting Three Types of Martensitic Transformations

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Lattice dynamics and structural stability of orderedFe3Ni,Fe3Pdand
Gruner
¹
,
Adeagbo
²
,
Zayak
³

et al. 2010
Phys. Rev. B

Lattice dynamics and structural stability of orderedFe3Ni,Fe3Pdand
Gruner
¹
,
Adeagbo
²
,
Zayak
³

et al. 2010
Phys. Rev. B