Elastic constants and their pressure dependences in ${\mathrm{Cd}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{Mn}}_{\mathrm{x}}$Te with 0≤x≤0.52 and in ${\mathrm{Cd}}_{0.52}$${\mathrm{Zn}}_{0.48}$Te

We have measured ultrasonic transit times to determine the elastic constants of ${\mathrm{Cd}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Mn}}_{\mathrm{x}}$Te crystals with 0≤x≤0.52 and of ${\mathrm{Cd}}_{0.52}$ ${\mathrm{Zn}}_{0.48}$Te at 296 K using hydrostatic pressures up to 4 kbar. It is found that Mn, but not Zn, weakens the zinc-blende crystal structure and makes it less stable under pressure. Applying a modified Born criterion to our data, we deduce the pressure expected to cause the transition to the rocksalt structure in each compound. The influence of Mn we attribute to Mn 3d orbitals hybridizing into the tetrahedral bonds.