SPECIAL FEATURES OF THE EXCHANGE INTERACTION OF SPIN AND ACOUSTIC WAVES IN ANTIFERROMAGNETS.

It is shown that a very small deviation of the applied magnetic field from the easy-axis direction results in a strong exchange coupling between spin and acoustic waves in fields close to the spin-flop field. This effect can explain large peaks in the absorption of longitudinal acoustic waves which were observed for MnF//2, Cr//2O//3, and alpha -FeO//3 crystals when the angle between the easy axis and the applied field was such that there was no domain structure in the sample. It should also lead to analogous peaks in the absorption of transverse acoustic waves with wave vector k and polarization vector e//t not in the basal plane of the crystal under study.