Ultrasonic studies below Tc in amorphous rare earth‐iron alloys

Measurements of the velocity of sound as a function of magnetic field are presented for amorphous DyFe2 and HoFe2. The samples were prepared by rapid sputtering. Measurements were taken over a series of temperatures from above to well below the magnetic transition temperatures of both specimens. In DyFe2 shear waves polarized parallel to the field were observed to propagate more slowly than those polarized perpendicular to it. The velocity difference increased with decreasing temperature below the transition temperature becoming one percent of the velocity at sixty percent of the transition temperature. No such mode splitting was observed in HoFe2 down to seventy percent of its transition temperature. Comparison is made with a similar room temperature measurement in a‐TbFe2 and with magnetostriction measurements.