Domain observation and magnetostriction in Tb0.3Dy0.7Fe2 twinned single crystals

Abstract

The ternary alloy Tb0.3Dy0.7Fe2 (Terfenol-D) exhibits the largest known magnetostriction to anisotropy ratio near room temperature. To better determine the interaction between the elastic and magnetic properties of this material, a stoichiometric twinned single crystal was grown by a free-standing float-zone technique. Observations using Scanning electron microscopy and energy dispersive spectroscopy confirmed that the sample was free of the normally present rare-earth (RE) eutectic phase and simultaneously free of Widmanstatten precipitate (RE Fe3). A bar with (111) and (11̄0) faces perpendicular to the [112̄] growth direction was examined. Also, a [111̄] slab was cut from the boule. This slab was studied along the [111̄] and [11̄0] directions with prestress applied along the [111̄]. This is the first report of the effects of applying prestress and magnetic fields in a direction not collinear with the [112̄] growth direction. From magnetization (M) and magnetostriction (λ) measurements as a function of field, prestress, and temperature, we determined the hysteresis and saturation parameters. These measurements do not indicate the [11̄0] λ and M behaviors found previously for RE-rich Terfenol-D. Domain observations with differential phase contrast and x-ray topography have shown different orientations in the twin and parent sections of the [111̄] specimen. The observed structures can be interpreted as arising from domains with magnetization components normal to the surface. The domain observations on the (111) and (11̄0) bar faces and on the [111̄] slab correlate with each other with respect to orientations and domain interpretations.