Magnetic structure changes in amorphous RE-Fe2 alloys as detected by ultrasonic measurements

Abstract The velocity of ultra sound as a function of magnetic field was measured from room temperature to 80 K in amorphous DyFe 2 and TbFe 2 . Shear waves polarized parallel to the magnetic field had lower velocities than those polarized perpendicular to the field. The velocity as a function of field reached a minimum in parallel case at a field which increased as the temperature was lowered. The difference between the perpendicular and parallel moduli at 25 kOe has a maximum at roughly one-third the Curie temperature in both samples. A discussion is presented to the relation between these effects and the nature of the magnetic structure of rare earth-iron amorphous materials.