It is shown that the four-wave mixing technique can be used as a spect
roscopic tool for studying the properties of bistable centers in semic
onductors. Two metastable centers with different lattice relaxation en
ergy have been identified in the Cd1-xMnxTe1-ySex: In crystal. The pow
er dependence of the FWM signal provides additional support for the ''
negative-U'' model of metastable centers in this material. (C) 1998 El
sevier Science B.V. All rights reserved.