Uniaxial stress dependence of the [ζ ζ 0]-TA 2 anomalous phonon branch in Ni 2MnGa

Abstract

Results of neutron scattering experiments on single crystals of Ni 2MnGa as a function of uniaxial stress and temperature are reported. Emphasis is placed on the behavior of the low-energy part of the [ζ ζ 0] TA 2 phonon branch and the associated premartensitic phase transformation. The dip in the phonon dispersion curve is stress-dependent and shifts from ζ = 0.33 for zero stress to ζ = 0.36 for an applied stress of 95 MPa. The energy of the soft phonon decreases with increasing stress. The premartensitic transition temperature is increased from 265 K in the unstrained sample to ≈ 300 K at 95 MPa.