Nonlinear Dependence of Velocity of Elastic Waves on Uniaxial Tension in Single-Crystal Terbium

A.Andrianov, A.A.Korobov (Department of Acoustics, Faculty of Physics, Moscow State University, Moscow, Russia)

e-mail: andr@lt.phys.msu.su

The results of experimental investigation of dependencies of a longitudinal sound velocity on uniaxial tension in a terbium single crystal are presented. Tension was applied along the hexagonal axis and changed in an interval 0-60 MPa. The ultrasound was propagated perpendicularly to the hexagonal axis. Measurements were performed in a pulse mode at room temperature. Under the pressure ~30 MPa nonlinear dependence of sound velocity on the static pressure was observed. The results can be treated as the following. Terbium is rare-earth metal with a hexagonal close-packed crystallographic structure. When applying uniaxial tension along a hexagonal axis the change of parameters of a lattice without change of its symmetry occurs. This change causes, at pressure 30 MPa, a change of topology of Fermi surface: electronic topological transition, which results in anomaly in behavior of some physical properties, including velocity of elastic waves.


Section : 2