Coupling of elastic waves to the "nonactivated" spin-flop mode in MnF2

The coupling of the nonactivated spin-flop mode in MnF2 to two elastic modes via the linear magnetoelastic interaction is shown to lead to discontinuities at the spin-flop transition in the elastic constants c11 and c=12(c11-c12). The directions of easy magnetization in the basal plane are determined to be the equivalent [110] axes. © 1970 The American Physical Society.