LARMOR PRECESSION OF MN2+ MOMENTS INITIATED BY THE EXCHANGE FIELD OF PHOTOINJECTED CARRIERS IN CDTE CD1-XMNXTE QUANTUM-WELLS/

We observed dynamical processes of the magnetic moments of photoinject ed carriers and resultant perturbed magnetic moment of Mn2+ ions in Cd Te/Cd1-xMnxTe quantum wells by means of the femtosecond time-resolved magneto-optical Kerr rotation measurement in transverse magnetic field s. The time-resolved Kerr rotation signal shows that the Larmor preces sion of Mn2+ moment is initiated by photoinjected carriers. In particu lar, we observed a time delay in terms of the phase and an amplitude o f Mn2+ beats as a function of the external field to confirm the mechan ism of perturbing the Mn2+ moment, i.e., a transient p-d exchange fiel d, proposed in earlier studies. The motion of the Mn2+ moment is also simulated by the Bloch model including the impulsive transverse exchan ge fields produced by the conduction electron and heavy-hole spins. Fr om this it is found that the exchange field of the heavy-hole spin con tributes dominantly to tipping the Mn2+ moment away from the external field axis. The exchange field estimated by the Bloch model so as to f it experimental data is in reasonable agreement with the exchange fiel d estimated from p-d exchange interaction, which also supports the abo ve mechanism.