  We report on magnetic field induced oscillations of the photon echo signal
from negatively charged excitons in a CdTe/(Cd,Mg)Te semiconductor quantum
well. The oscillatory signal is due to Larmor precession of the electron spin
about a transverse magnetic field and depends sensitively on the polarization
configuration of the exciting and refocusing pulses. The echo amplitude can be
fully tuned from maximum down to zero depending on the time delay between the
two pulses and the magnetic field strength. The results are explained in terms
of the optical Bloch equations accounting for the spin level structure of
electron and trion.
