Lattice dynamics in magnetic superelastic Ni-Mn-In alloys: Neutron scattering and ultrasonic experiments


Moya X. , GONZALEZ-ALONSO D., MANOSA L., PLANES A., Garlea V. O. , Lograsso T. A. , ...More

PHYSICAL REVIEW B, vol.79, no.21, 2009 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 79 Issue: 21
  • Publication Date: 2009
  • Doi Number: 10.1103/physrevb.79.214118
  • Title of Journal : PHYSICAL REVIEW B

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 Ni(50)Mn(34)In(16) 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 TA(2) branch are relatively low and it exhibits a small dip anomaly at a wave number xi(0) approximate to 1/3, which softens with decreasing temperature. Associated with the softening of this phonon, we also observed the softening of the shear elastic constant C' = (C(11)-C(12))/2. 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 < 1 (1) over bar0 > directions. Additionally, we measured low-lying phonon-dispersion branches and elastic constants in applied magnetic fields aimed to characterize the magnetoelastic coupling.