High-pressure effects on high-field magnetophotoluminescence in ${\mathrm{Cd}}_{1\mathrm{-}\mathit{x}}$${\mathit{M}}_{\mathit{x}}$Se (M=Mn,Co)

Photoluminescence measurements have been performed in the diluted magnetic semiconductors ${\mathrm{Cd}}_{1\mathrm{-}\mathit{x}}$${\mathit{M}}_{\mathit{x}}$Se(M=Mn,Co) at 4.2 K under combined extreme conditions of high hydrostatic pressure up to 2 GPa and high magnetic field up to 27 T. The field-induced shift of the energy of the A exciton is enhanced significantly by pressure in ${\mathrm{Cd}}_{0.988}$${\mathrm{Co}}_{0.012}$Se and ${\mathrm{Cd}}_{0.95}$${\mathrm{Mn}}_{0.05}$Se, while it is rather reduced in ${\mathrm{Cd}}_{0.75}$${\mathrm{Mn}}_{0.25}$Se. The former effect arises from strengthening of the p-d exchange interaction by pressure, and the latter effect shows that pressure strengthens not only the p-d exchange interaction but also the antiferromagnetic coupling among magnetic ions. The anisotropy energy of the trigonal crystal field is sensitive to pressure, as well. When magnetic field is applied perpendicular to the c axis of the wurtzite structure, the pressure effect on the exciton energy depends strongly on the external magnetic field, demonstrating that the transverse exchange field critically competes with the trigonal crystal field and the spin-orbit coupling. © 1996 The American Physical Society.