Phonon softening in Ni46.8Ti50Fe3.2

Abstract

Inelastic neutron scattering has been used to study the premartensitic phase transition in NiTi:Fe. A phonon softening of the [110]-T${\mathrm{A}}_2$ branch near $q_{\mathrm{I}}=(\frac{1}{3},\frac{1}{3},0)$ has been observed. This is near the wave vector where incommensurate superlattice peaks appear below the premartensitic-phase-transition temperature of 232 K. This phonon softening can be understood in terms of a Fermi-surface-driven electron-phonon anomaly.