Domain structures in polycrystalline Tb0.27Dy0.73Fe2 (Terfenol) in the applied field region of optimum magnetoelastic properties

Abstract

A Bitter colloid technique has been used to study field-induced domain changes in polycrystalline Tb0.27Dy0.73Fe2 (Terfenol) in the bias field region where the incremental strain and magnetomechanical coupling coefficients are known to maximize. The dominant feature of the structures in this critical field region was found to be the formation of stripelike domains with their long directions inclined at large angles to the applied field. One of a series of optical micrographs showing domain changes at increasing applied fields, and electron micrographs of the dried colloid showing finer details of these domains at chosen bias fields, are presented for grains whose orientations have been determined by x-ray methods. It was found that the majority of these domains were separated by 71° walls. Such an arrangement might be expected in view of the high magnetoelastic coefficients characteristic of this field region.