Vibrational properties of Ni–Mn–Ga shape memory alloy in the martensite phases
Studying the phonon dispersion of the ferromagnetic shape memory alloy system Ni–Mn–Ga gives insight into the mechanism of the martensite transition and the forces driving the transition. Transformation of austenite single crystals under uniaxial stress results in the coexistence of two martensitic...
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2013-01-01
|
| Series: | New Journal of Physics |
| Online Access: | https://doi.org/10.1088/1367-2630/15/12/123016 |
| _version_ | 1797751711150899200 |
|---|---|
| author | Semih Ener Tarik Mehaddene Björn Pedersen Michael Leitner Jürgen Neuhaus Winfried Petry |
| author_facet | Semih Ener Tarik Mehaddene Björn Pedersen Michael Leitner Jürgen Neuhaus Winfried Petry |
| author_sort | Semih Ener |
| collection | DOAJ |
| description | Studying the phonon dispersion of the ferromagnetic shape memory alloy system Ni–Mn–Ga gives insight into the mechanism of the martensite transition and the forces driving the transition. Transformation of austenite single crystals under uniaxial stress results in the coexistence of two martensitic variants with perpendicular modulation vector. Here we report on inelastic neutron scattering studies of martensite crystals with off-stoichiometric compositions, varying from non-modulated (NM) to five- (5M) and seven- (7M) layer modulated martensite phases. Both the 5M and 7M crystals show fully commensurate satellite peaks along [ $\xi \bar {\xi }$ 0], corresponding to the five- and seven-layer modulation. These superstructure peaks become Γ-points of the modulated structure. Due to the coexistence of two variants within the (001) plane, both new acoustic phonons reflecting the modulation vector [ $\xi \bar {\xi }$ 0] and acoustic TA _2 [ ξ ξ 0] phonons corresponding to the non-modulated direction are observed. The latter display a pronounced softening around ξ = 0.2–0.4 when approaching the martensite–austenite transition from above and below, i.e. this soft mode has lowest frequency at the transition temperature. Overall the phonon dispersion of the austenite and martensite phase resemble each other very much. The coexistence of two martensitic variants after uniaxial transformation explains the particular behaviour of the low-energy excitations, in contrast to previous interpretations involving charge-density waves and associated phason modes. |
| first_indexed | 2024-03-12T16:52:33Z |
| format | Article |
| id | doaj.art-55dc4edf5c5c4e5c9ab606daafa216e0 |
| institution | Directory Open Access Journal |
| issn | 1367-2630 |
| language | English |
| last_indexed | 2024-03-12T16:52:33Z |
| publishDate | 2013-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | New Journal of Physics |
| spelling | doaj.art-55dc4edf5c5c4e5c9ab606daafa216e02023-08-08T11:06:23ZengIOP PublishingNew Journal of Physics1367-26302013-01-01151212301610.1088/1367-2630/15/12/123016Vibrational properties of Ni–Mn–Ga shape memory alloy in the martensite phasesSemih Ener0Tarik Mehaddene1Björn Pedersen2Michael Leitner3Jürgen Neuhaus4Winfried Petry5Physics Department, Technische Universität München , James-Franck-Straße 1, 85748 Garching, GermanyPhysics Department, Technische Universität München , James-Franck-Straße 1, 85748 Garching, GermanyHeinz Maier–Leibnitz Zentrum (MLZ), Technische Universität München , Lichtenbergstraße 1, 85748 Garching, GermanyPhysics Department, Technische Universität München , James-Franck-Straße 1, 85748 Garching, Germany; Heinz Maier–Leibnitz Zentrum (MLZ), Technische Universität München , Lichtenbergstraße 1, 85748 Garching, GermanyHeinz Maier–Leibnitz Zentrum (MLZ), Technische Universität München , Lichtenbergstraße 1, 85748 Garching, GermanyPhysics Department, Technische Universität München , James-Franck-Straße 1, 85748 Garching, Germany; Heinz Maier–Leibnitz Zentrum (MLZ), Technische Universität München , Lichtenbergstraße 1, 85748 Garching, GermanyStudying the phonon dispersion of the ferromagnetic shape memory alloy system Ni–Mn–Ga gives insight into the mechanism of the martensite transition and the forces driving the transition. Transformation of austenite single crystals under uniaxial stress results in the coexistence of two martensitic variants with perpendicular modulation vector. Here we report on inelastic neutron scattering studies of martensite crystals with off-stoichiometric compositions, varying from non-modulated (NM) to five- (5M) and seven- (7M) layer modulated martensite phases. Both the 5M and 7M crystals show fully commensurate satellite peaks along [ $\xi \bar {\xi }$ 0], corresponding to the five- and seven-layer modulation. These superstructure peaks become Γ-points of the modulated structure. Due to the coexistence of two variants within the (001) plane, both new acoustic phonons reflecting the modulation vector [ $\xi \bar {\xi }$ 0] and acoustic TA _2 [ ξ ξ 0] phonons corresponding to the non-modulated direction are observed. The latter display a pronounced softening around ξ = 0.2–0.4 when approaching the martensite–austenite transition from above and below, i.e. this soft mode has lowest frequency at the transition temperature. Overall the phonon dispersion of the austenite and martensite phase resemble each other very much. The coexistence of two martensitic variants after uniaxial transformation explains the particular behaviour of the low-energy excitations, in contrast to previous interpretations involving charge-density waves and associated phason modes.https://doi.org/10.1088/1367-2630/15/12/123016 |
| spellingShingle | Semih Ener Tarik Mehaddene Björn Pedersen Michael Leitner Jürgen Neuhaus Winfried Petry Vibrational properties of Ni–Mn–Ga shape memory alloy in the martensite phases New Journal of Physics |
| title | Vibrational properties of Ni–Mn–Ga shape memory alloy in the martensite phases |
| title_full | Vibrational properties of Ni–Mn–Ga shape memory alloy in the martensite phases |
| title_fullStr | Vibrational properties of Ni–Mn–Ga shape memory alloy in the martensite phases |
| title_full_unstemmed | Vibrational properties of Ni–Mn–Ga shape memory alloy in the martensite phases |
| title_short | Vibrational properties of Ni–Mn–Ga shape memory alloy in the martensite phases |
| title_sort | vibrational properties of ni mn ga shape memory alloy in the martensite phases |
| url | https://doi.org/10.1088/1367-2630/15/12/123016 |
| work_keys_str_mv | AT semihener vibrationalpropertiesofnimngashapememoryalloyinthemartensitephases AT tarikmehaddene vibrationalpropertiesofnimngashapememoryalloyinthemartensitephases AT bjornpedersen vibrationalpropertiesofnimngashapememoryalloyinthemartensitephases AT michaelleitner vibrationalpropertiesofnimngashapememoryalloyinthemartensitephases AT jurgenneuhaus vibrationalpropertiesofnimngashapememoryalloyinthemartensitephases AT winfriedpetry vibrationalpropertiesofnimngashapememoryalloyinthemartensitephases |