Magneto-Elastic Interactions in Gadolinium

The effect of the change in easy direction of magnetization on the elastic constants $c_{33}$ and $c_{44}$ has been measured in single-crystal gadolinium by means of a pulse-echo technique. One of the constants $c_{33}$ exhibited a sharp decrease of about 2% over the temperature range -37 to -51°C after which it slowly returned to its normal, monotonic increasing behavior with decreasing temperature. Magnetic fields of up to 8 kOe, either parallel or perpendicular to the unique axis of the hexagonal crystal, were applied to the sample. These decreased the absolute magnitude of the change in $c_{33}$. It is thought that the acoustic wave is coupled to the spin structure by volume magnetostriction.