Coherent spin dynamics of localized ${\mathrm{Mn}}^{2+}$ spins are studied in a single (Cd,Mn)Te/(Cd,Mg)Te diluted-magnetic-semiconductor quantum well using a two-color pump-probe Faraday rotation technique. The initial phase of the manganese Larmor precession in magnetic field is measured at the maximum of exciton absorption, where the probe is set. The pump is detuned at lower energies with weak absorption of the quantum well excitons. The measured dependence of the initial phase on the pump power allows us to conclude that the manganese Larmor precession is induced by two mechanisms: the exchange field of optically oriented photogenerated holes and the magnetic field resulting from the inverse Faraday effect. The initial phase depends also on the strength of the external magnetic field. The modeled dependence of the phase on the pump power in various magnetic fields is in good agreement with the experimental data.

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• Faraday effect
• Spin coherence
• Spin dynamics
• Quantum wells