Variations in strain amplitude and phase in a cylindrical specimen of Tb/sub 0.3/Dy/sub 0.7/Fe/sub 1.95/ in an AC magnetic field

In the light of differences between magnetostrictive strains measured on the surface of Terfenol with strain gauges and from a dilatometer, an optical interferometer has been used to probe the spatial variations of the magnetostrictive strains across the plane surface of a polished disc (6 mm diameter, 1 mm thick) of grain-orientated Tb/sub 0.27/Dy/sub 0.73/Fe/sub 1.95/ DC and AC fields ( approximately 15 kA/m and approximately 440 A/m RMS, respectively) were applied normal to the disk surface parallel to the