Magnetomechanical effects in textured polycrystalline Tb76Dy24

Abstract

Uniaxial stress-strain measurements were performed on polycrystalline Tb76Dy24 alloys which exhibit "giant magnetostriction" at cryogenic temperatures. The Young's moduli were reduced by up to a factor of five at 77 K, in comparison to their values at 300 K. We attribute this reduction to a mechanical compliance from domain rotation. Large mechanical hysteresis is also found in nominally elastic stress-strain curves measured below the Curie temperature. Hysteretic curves from 0 to 25 MPa demonstrate up to 19% dissipation of the applied mechanical energy. The anisotropy of thermal expansion was also measured and used as a parameter for the degree of crystallographic texture. This anisotropy was correlated to bulk magnetostriction and to mechanical hysteresis.