Phason mode in the incommensurate martensitic phase of Ni2MnGa - observed by neutron spectroscopy
Loading...
Date
2006-12-04
Journal Title
Journal ISSN
Volume Title
Publisher
Australian Institute of Physics
Abstract
The ferromagnetic shape-memory alloy Ni2MnGa, of technological interest as a magnetically driven actuator, undergoes a martensitic transformation from a cubic austenite to a tetragonally distorted martensite structure. Previous inelastic neutron scattering experiments, performed in the martensite phase, show an anomaly in the phonon dispersion for the [110] transverse acoustic branch TA2 [1]. This anomaly is identified (in ab-initio calculations through examination of Fermi-surface nesting and electron-phonon coupling) as a Kohn anomaly [2] and occurs at a wave vector incommensurate with the underlying lattice. Elastic neutron scattering reveals a modulation of the martensite phase with this incommensurate wave vector [1]. In very recent inelastic experiments, performed with cold- and thermal-neutron triple-axis-spectrometers, in addition to the known acoustic branch a new dispersive branch was found, showing all characteristics of a phason mode. In our interpretation, the new mode is caused by a charge-density-wave in the incommensurately distorted lattice. Inelastic neutron scattering is the only technique able to unambiguously detect a phason branch - and successful examples are rare.
[1] P. Vorderwisch and S.M. Shapiro, submitted
[2] C. Bungaro et al., Phys. Rev. B 68 (2003) 134104
Description
Keywords
Ferromagnetic materials, Alloys, Actuators, Martensitic steels, Transformations, Austenite, Inelastic scattering, Spectrometers
Citation
Vorderwisch, P., Shapiro, S., Habicht, K., Hradil, K., & Schneider, H. (2006). Phason mode in the incommensurate martensitic phase of Ni2MnGa - observed by neutron spectroscopy. Paper presented at the Australian Instute of Physics 17th National Congress 2006, Brisbane Convention and Exhibition Centre, Brisbane Australia, Sunday 3 - Friday 8 December 2006. Retrieved from: https://www.aip.org.au/resources/Documents/Congress/AIPCongress-2006-Program.pdf