Statistical fluctuations of the magnetization are measured on the nanometer scale. As the experimental monitor we use the characteristic photoluminescence signal of a single electron-hole pair confined in one magnetic semiconductor quantum dot, which sensitively depends on the alignment of the magnetic ion spins. Quantitative access to statistical magnetic fluctuations is obtained by analyzing the linewidth broadening of the single dot emission. Our all-optical technique allows us to address a magnetic moment of only approximately equal 100 micro(B) and to resolve statistical changes on the order of a few micro(B).

present the results of magnetoluminescence study of ZnSe:CdMnSe quantum dots samples in a magnetic field up to 11 T both in the Faraday and Voigt geometries at liquid He temperatures and various levels of laser excitation. We found that the intensity of the quantum dot photoluminescence strongly increases (up to two orders of magnitude) in the Faraday geometry and only slightly (∼ 1.5 times) in the Voigt geometry within the range of B=0-11 T. We explain the strong increase of the photoluminescence in the Faraday geometry within the frame of the spin-dependent Auger recombination of excitons through Mn ions. We relate the observed anisotropy of the quantum dot emission with the high anisotropy of the hole spins in QDs. We present a theoretical model which allows us to obtain selection rules for the Auger transition and thoroughly explains experimental results. The selections rules allow to explain characteristic fitures in single quantum dot spectra.

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Mechanisms of non-radiative recombination of electron-hole complexes in Cd(Mn)Se/Zn(Mn)Se quantum dots accompanied by interconfigurational excitations of Mn(2+) ions are analyzed within the framework of the single-electron model of deep 3d levels in semiconductors. In addition to the mechanisms caused by Coulomb and exchange interactions, which are related because of the Pauli principle, another mechanism due to sp-d mixing is considered. It is shown that the Coulomb mechanism reduces to long-range dipole-dipole energy transfer from photoexcited quantum dots to Mn(2+) ions. The recombination due to the Coulomb mechanism is allowed for any states of Mn(2+) ions and e-h complexes. In contrast, short-range exchange and sp-d recombinations are subject to spin selection rules, which are the result of strong lh-hh splitting of hole states in quantum dots. Estimates show that efficiency of the sp-d mechanism can considerably exceed that of the Coulomb mechanism. The phonon-assisted recombination and processes involving the upper excited states of Mn(2+) ions are studied. The increase in PL intensity of an ensemble of quantum dots in a magnetic field perpendicular to the sample growth plane observed earlier is analyzed as a possible manifestation of the spin-dependent recombination.

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