The effects of magnetic annealing and compressive stress on the magnetic properties of the rare earth-iron compound Terfenol-D

Abstract

The rare earth-iron compound Terfenol-D (Tb x Dy 1− x Fe y with x ≈ 0.3 and y ≈ 1.92) is known to be highly magnetostrictive (1500–2000 ppm) and to possess a magnetomechanical coupling coefficient of around 0.7, properties which are affected by the application of compressive stress. Measurements have been made of the variation in the magnetostriction (λ), induction ( B), magnetostrain coefficient ( d 33), permeability (μ σ) and magnetomechanical coupling ( k 33) as a function of applied field and uniaxial compressive stress in the range 0 to 20 MPa and remeasured after being subjected to a magnetic heat treatment. After magnetic annealing, increases in the magnetostriction in the absence of an applied pre-stress are evident. However, under the conditions used in these annealing experiments, this improvement in the magnetostriction is at the expense of a reduced μ σ and d 33.