Abstract
Neutron scattering and ultrasonic methods have been used to study the lattice dynamics of two single crystals of Ni-Mn-In Heusler alloys close to magnetic superelastic composition. The paper reports on the experimental determination of the low-lying phonon-dispersion curves and the elastic constants for this alloy system. We found that the frequencies of the branch are relatively low and it exhibits a small dip anomaly at a wave number , which softens with decreasing temperature. Associated with the softening of this phonon, we also observed the softening of the shear elastic constant . Both temperature softenings are typical for bcc-based solids which undergo martensitic transformations and reflect the dynamical instability of the cubic lattice against shearing of {110} planes along directions. Additionally, we measured low-lying phonon-dispersion branches and elastic constants in applied magnetic fields aimed to characterize the magnetoelastic coupling.
- Received 4 March 2009
DOI:https://doi.org/10.1103/PhysRevB.79.214118
©2009 American Physical Society