Optical observation of closure domains in Terfenol-D single crystals

Optical differential interference contrast microscopy is used to observe the topological features in surfaces of single crystal Terfenol-D (Tb_0.3Dy_0.7Fe_1.95) which arise from macroscopic lattice tilts due to the magnetostrictive strain between neighboring magnetic domains at the surface. The domain configurations observed can all be interpreted as being composed of low-energy 71 degrees and 109 degrees walls which have components of magnetization normal to the surface. Domain widths on the order of 2 mu m can readily be resolved. Observations from surfaces polished parallel to [110] and [112] are presented as a function of temperature, between 250 K and 350 K, and as a function of magnetic field applied parallel to the specimen surface.