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file = NMR˙RSA˙24feb14˙final.tex, printing time = 12 : 01) Resonant cooling of different nuclear isotopes manifested in optically-induced nuclear magnetic resonances (NMR) is observed in n-doped CdTe/(Cd,Mg)Te and ZnSe/(Zn,Mg)Se quantum wells and for donor-bound electrons in ZnSe:F and GaAs epilayers. By time-resolved Kerr rotation used in the regime of resonant spin amplification we can expand the range of magnetic fields where the effect can be observed up to nuclear Larmor frequencies of 170 kHz. The mechanism of the resonant cooling of the nuclear spin system is analyzed theoretically. The developed approach allows us to model the resonant spin amplification signals with NMR resonances.

Spin coherence of resident electrons and holes is measured in ZnSe‐based quantum wells by means of time‐resolved Kerr rotation technique. At a temperature of 1.8 K spin dephasing time for localized electrons can be as long as 33 ns, and for holes of 0.8 ns. Electron spin precession is clearly observed in a wide temperature range up to 230 K. The electron spin dephasing becomes much shorter of 0.2 ns for the quantum well with a high‐density electron gas. Using vector magnet all components of the g‐factors tensor are evaluated for the electrons and heavy‐holes, revealing strong anisotropy for the heavy‐holes.

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Zeeman splitting of the quantum confined states of excitons in the InGaAs quantum wells (QWs) is experimentally found to strongly depend on the quantization energy. Moreover, it changes its sign when the quantization energy increases with the decrease of the QW width. In the 87-nm QW, the sign change is observed for the excited quantum confined states, which are above the ground state only by a few meV. A two-step approach for the numerical solution of two-particle Schrödinger equation with taking into account for the Coulomb interaction and the valence-band coupling is used for theoretical justification of the observed phenomenon. The calculated variation of the g-factor convincingly follows the dependencies obtained in the experiments.